Bullet Proofing Walls | Resistant Wall Construction

Bullet proofing walls and the design thereof. You may consider to consult with a professional within the “hardened structures” industry.

With that said, this article originally published during 2014. It received excellent and informative discussion which I suggest you read down in the comments below.

The basis for the original post came from an online report (forgot how / where I found it). It covered various techniques being considered for bullet resistant wall construction for the city of Boulder, Colorado. One of which I briefly outlined below.

In particular they were looking for economical solutions (though apparently less than ideal).

It inspired lots of discussion. In particular pointing out one major flaw in the specific technique described (read on to discover it). As well as excellent alternative ideas, some from professionals in this industry, and some references to “bullet proof wall cheap” (using sand or gravel). At least “cheap” comparative to other techniques.

So I will segue to the OP which is as follows, which may inspire further discussion.

For those concerned about their security in this regard (bullet resistant wall construction). This is one technique using poured concrete.

Bullet Proofing Walls With Poured Concrete

(actually, we’re talking about bullet resistance)

Based on these tests, it is my professional recommendation, when practical, that we utilize the combination of Oriented Strand Board (OSB) and concrete. For new construction this combination appears to offer the best results at a cost far less than the commercially available ballistic fiberglass.”

There are many ways to build a bullet resistant wall. Or to beef up the resistance to slow or stop a bullet. This particular recommendation was made to the city of Boulder following a series of bullet penetration tests conducted by the city facility manager there.

He concluded that the best bullet resistant wall construction (versus cost) would be poured concrete filling the cavity between 2″X4″ studs, using 1-1/8″ OSB (oriented strand board) fastened to both sides, followed by 5/8″ Gypsum.

The OSB would be screwed to to the 2×4’s and used as a material strong enough to hold the poured concrete. Then apparently left in place afterwards as an integral part of the wall. The Gypsum (drywall) is fastened for the interior wall aesthetic appearance.

Bullet Caliber Penetration Tests

They performed bullet penetrations tests. This determined the ability to withstand penetrations by a number of commonly used bullets.

9mm, .45 auto, .357, .44, 12 ga. slug, .223, .270 Win

The calibers were selected based on press coverage of incidents around the nation, as weapons-calibers commonly used in attacks on citizens.

All test shots were from 7 yards downrange.

Materials Cost

The materials cost for the recommended solution above (at the time) was determined to be a little more than $3 per square foot (approximately $100 for a 4×8 section).

Of course your own cost of materials may vary. Consider labor costs. Diy or otherwise. At the time of the recommendation, the labor costs were estimated to be similar to the materials cost itself.

Note: If seriously considering constructing a bullet-resistant wall such as this (and looking to save cost and weight). Fill the wall only 4-feet high. Or 4×8 sections sideways. This will still maintain a safe zone from that height to the floor.

Concrete Weight Density

Typically, concrete has a density of 150 pounds per cubic foot. This means that a block of concrete that is one foot wide, one foot long, and one foot high would weigh 150 pounds.

The gap in a 2×4 stud constructed wall (studs are actually 1.5 x 3.5) is approximately 8.6 – 9 cubic feet within a 4×8 section (depending on stud spacing). Therefore, each 4×8 section when filled with concrete will have a downward force weight of approximately 1,300 pounds.

If you’re filling to a height of 4′ then you’re looking at about 160-lbs per linear foot.

If you’re filling the entire wall, then you’re looking at about 320-lbs per linear foot.

Be sure that your floor and foundation can support it! Properly support the walls using techniques to avoid toppling!

Note: Plywood is stronger than OSB and resists moisture better. It is more expensive – although you won’t need 1-1/8″ (OSB) – while 3/4″ (plywood) should suffice.

There are other ways to accomplish this.
This is for educational-informational purposes only.
When in doubt, get architectural-engineering advice.
Check your own local codes and do your own due-diligence.

The bullet/ballistic resistance of concrete masonry

From the National Concrete Masonry Association

The actual resistance of concrete masonry assemblies to high velocity projectiles such as bullets varies considerably depending on the details of the assembly and the type and energy of the projectile.

While many tests have been conducted through the years documenting the ballistic resistance of concrete masonry construction, much of this research is not available in the public domain. The most current published comprehensive study was conducted in Canada by the Canadian Masonry Research Institute and the Royal Canadian Mounted Police as reported in Resistance of Exterior Walls to High Velocity Projectiles. A key conclusion of this report noted that:

“Walls finished with either a clay brick or concrete brick veneer prevented all but the 0.50 Browning from complete penetration of the wall assembly.”

Although the firearms and bullets used in this study do not exactly match Underwriters Laboratories bullet resistance levels under UL 752, Standard for Bullet-Resisting Equipment, (the standard often cited for bullet resistance), a comparison can be made by adjusting for the impact energy level as shown in the table below.

Before the Canadian study, most published ballistic testing on concrete masonry walls was carried out during World War II to make sure that adequate protection was provided for transformers, switching stations, and similar installations subject to sabotage.

Wall Section Descriptions:

A. Concrete masonry or clay masonry brick veneer with a nominal thickness of 90 mm (4 in.).

B. 150 mm (6 in.) nominal hollow concrete masonry units.

C. 150 mm (6 in.) nominal split-face hollow architectural concrete masonry units

D. Multi-wythe wall with either 90 mm (4 in.) nominal clay or concrete masonry brick with 150 mm (6 in.) nominal hollow concrete masonry unit backup.

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  1. This is some very limited protection offered by this method. However as a Licensed Architect in the Hardened Structures industry I cannot endorse this method.

    Please consider the following,
    2×4 stud walls are built at 16″ on center, the stud is 1.5″ thick. Basically you have a softwood material for a wall every 16″, nearly 10% of your wall is soft. in a sustained fire event (“suppressive fire” to my fellow combat arms peers), some rounds will get through at the soft wood. This would be an unacceptable design failure. (I would not do this method to protect my child and neither should you)

    Next, a 2×4 is 3.5″ wide. 3.5″ and 8 feet tall is a VERY narrow cavity to pour concrete into. Various aggregate (gravel) sizes are used in concrete mix design and a 3.5″ wall cavity could have a very high probability of voids in the wall.

    Also regarding 3.5″ thickness and a sustained fire event, this thin wall cross section will experience degradation much sooner than thicker sections of concrete.

    In our designs we baseline 8″ of concrete as a bare minimum. (most are 16″ to 24″ but other threat types are being considered in the engineering) Also We include a grid, (usually multiple grids) of rebar to hold the concrete together, designed and specified by structural engineers.

    I understand folks are looking for a low cost solution. Please allow me to offer the following adaptation of this design, which will have dramatically higher performance, for a very modest increase in cost.

    1. Switch to metal studs. The “C” channel shape of metal studs allows the concrete to fill the entire wall cavity. use the heaviest gauge your budget will allow and your tools can drive a self tapping screw. Usually a good driver can self tap through up to 16 gauge, but often 18 gauge is a working limit for faster productivity, but I would not feel bad if you could only use 20ga studs.

    2. Use 6″ studs at a minimum. A 6″ wide 8 foot tall cavity would be the minimum thickness I could recommend. (a double stud wall w/ 2 rows of 3.5″ or 4″ metal studs would be even better )Be sure when filling the wall with concrete you have a long piece of rod or rebar to use to push down the concrete to make certain there are no remaining voids or air pockets in your wall.

    3. Use higher strength concrete. Standard concrete from the plant is 3,000-3,500 psi, but you can request higher values, 5,000psi would be a great improvement for a modest price increase.

    Alternatively, many systems of ICF – insulated concrete form type walls have a default thickness of 8″ of concrete plus a system to add rebar. 8″ of 5,000 psi concrete with rebar is pretty good wall for non “AP” small arms protection.

    Always remember small arms are just one of a myriad bag of tools an aggressor will use to neutralize or eject a defender. Your air supply and fire resistance should be considered as well as resistance to breaching methods at doors and windows.

    Proven methods to harden defenses for these any many more threats are possible.

    1. Thanks for the informative response.


      Are any metal trusses and rafters available for use with a metal roof? I’m thinking fire.

      1. Yes, light gauge metal trusses exist. no that is not your best option for fire protection. Metal under load deforms until collapse in a fire event.

        Metal roofing is of some value. I live in big fire country, the wild fire guys tell me soffits and eaves are where the fires start.

        One solution for existing structures is intumescent paint. it is very pricey, $300 for 5 gallons, which only covers half as much as regular paint, plus two coats are needed. but two coats are worth an hour of tested and proven UL rated fire protection.

        A better structural solution than light gauge metal for fire resistance is heavy timber.

        This has long been known to char over and resist fire. There is a building code for this.

    2. Im thinking that using concrete is a really bad ideal fir Denver. Especially in 2x frame construction. They have very cold winters. Icf or real rock facade would be a much better ideal. Just an okie’s ideal.

    3. this a great piece of research, but aren’t a lot of shoots randomly and much larger calibers. Ak and 308 or even the 5.56. I’ve seen their after math of an. 308 and AK rounds on 6×6 trees and beams. that wall design does not give me feelings of safe happy security.

      1. If you reread the article, you’ll see they tested .223 (same as 5.56) and 270 Win (ballistics exceed 308 and are double those of the 7.62×39 (AK round)

    4. What do you think about lining the interior of metal walls with rock/gravel? Ive seen a few gambion walls and wondered about small arms stopping power.

  2. As a person with no options to rebuild I have often thought of how to add a layer of protection to walls to prevent bullet penetration. Unfortunately I don’t have many options. The best solution that I have conceived so far is to move several of our bookcases to the outer walls. As a packed bookcase of books adds a thickness of 6 to 10 inches (depending on the thickness of the books) its better than nothing. I know there are gaps above the books on each shelf so something can still get through. Its the best solution I have been able to come up with at this time.

    I also have 3 files cabinets which I would also move to the outer walls. I know these are not optimal solutions but it is better than nothing. I am also sure that there are some calibers that would penetrate even these options.

    1. Look up the product gigacrete.

      Applied like interior plaster, a 1″ layer over plywood was tested and shown to stop magnum handguns plus 7.62×39, the AK-47 ammunition, at indoor distances.

      This is actually quite impressive.

      I have samples of this product ready to construct boards for my own testing, so I’ll know more soon, but the videos were very impressive.

      1. J2H
        even gambion structure filled with dirt will work, 36” generally stops .50
        double offset row of 36” circulars holds up well, lots of material to come up with,
        set up like US forces utilize filled with a loader and stacked 2 high, i think generally 6’ across are excellent block for all sorts of threats

    1. This was just a technique that was apparently considered for the city of Boulder Colorado to be used for some portions of ‘at risk’ structures (they were not more specific than that as I recall the original report) and it was unclear whether they were considering this for new construction, or otherwise.

      They were looking for a cost-versus-reward method so that they could work within their budget (I was actually surprised that a government entity was working within a budget ;) ), and this is apparently what they came up with – which seems reasonable, given the evident testing with the calibers used.

      Like someone else already mentioned here, there is a vulnerability at the studs with sustained fire – however my suspicion is they were not budgeting for battle-hardened walls but more-so against a fairly unlikely shooting ‘incident’.

      Windows will always be a vulnerability unless big $$ are spent on bullet-proof glass. One could employ drop-down (or slide-across) steel plates I suppose – but now you’re getting into battle-bunker design…

      1. I’m a PI / Security Advisor of 25 years & my husband a Deputy. Bullet resistant film for windows (looks like car window tint) is available for @$40 a roll via Amazon & EBay. Heavy guage metal sheets run @$25 a panel. Both are resistant to lower calibre and can slow higher grades. Both can deflect direct injury from low grade explosions too. Better than “nothing” drywall alone.

  3. I have spent many years in the structural concrete business. The proposal to simply fill the cavity between 2 x 4 studs is not well thought out. To build a concrete wall you must first start with a footing that is designed to support the load and provide sufficient reinforcement to prevent the wall, that must bear directly on the footing, from toppling. Other things also must be addressed. The electric lines have to be in conduit. The list goes on.

    For those who have a slab on grade and are thinking of an interior safe room, the slab area beneath the concrete wall has to be designed to support the additional load.

    I recommend that a professional person design this properly for you.

      1. Off the top of my head the samurai Japanese had a very interesting method for making armour not from metal or anything u might think and live testin showed hell I think they stabbed and shot it with just about everything short of a Sherman tank and nothing made it thru real strong practically free in material costs

  4. MY $0.02.
    The idea I have come up with has not been tested and may have to wait until a SHTF scenario. Or until I can acquire such item and test at my range.

    But, my idea is to acquire steel man hole covers and place them upright along my exterior walls on the inside. Good for low cover and cannot be seen from the outside. I have noticed multiple such items all around the area I live in. Also would make for a nasty “pothole” in my surrounding intersections.

    Good, bad or what’s your opinion?

    Always looking for ideas and always offering ideas to help make (pun intended) bulletproof ideas.

    1. We will all do what we can Urban Redneck. I have sand bags in my shed. I figured I would pull back my fake lawn and fill the bags with the 1/4″ to dust material and stack in certain areas of the house. BTW, I do have 3/4″ plywood cut with bracing for my windows and doors. (Not bullet proof, but aides in security and blackout)

    2. Since the U.S. military is leaving the sand box overseas you should look into surplus collapsible Hesco Barriers being sold by our government. Once the Hesco barrier is set up, and filled with dirt and gravel, they will easily stop 50 cal rounds, plus they will deflect and absorb the blast from explosives too.

  5. Although I agree with the architect, that would be for new construction. I built my safe at home in a closet in my office, but didn’t want to upset the wife by removing the bathroom walls on the other side. I wouldn’t be alive if I tried that one.

    I removed the drywall, ripped the 2X4’s in half, leaving the corner studs. Installed 1/2″ hardi backer, caulked all corners extremely well. Installed 2 layers of 6″ mess concrete wire alternated to provide 3″ mesh. Installed 3/4″ fire treated plywood and caulked again. I screwed 3″ screws through the plywood into the cavity all over to provide a bond to the grout. I also used fire caulking in certain areas. Support braced the walls with 2×4’s, then pumped and poured construction grout in the cavity. If you do this, pour about 1-2 feet at a time and let it set up. My door is hollow metal door and frame, with a total of 5 non removable pin hinges with bolts extended into the door. I then poured the door cavity & frame as well. The ceiling and floor, I got lazy and installed 2 layers of 3/4″ fire treated plywood and 1 Hardi backer in between. I built this as my gun safe, as the costs for a really good gun safe was a lot more than doing this, and I don’t have a safe sitting in my home. I had also just came off a job and most materials were left over, but I have a 2′ x 4′-6″ safe. I also carpeted the walls, but you can use anything.

  6. Has anyone considered plate steel? One other thing to consider is EMPs. The next time you have an MRI, look at the construction of the room and how they handle the windows. Of course if you decide to do a two for one protection for any SHTF occasion, remember what to do for electricity. If you go for the 6 or 8 inch concrete wall, do you embed conduit or surface mount. If you’re heading to stave off an EMP, a generator in the house is a must, and all wires, metal pipes must be able to be isolated from the EMP so it does not enter the house through any metal path.

    1. Plate steel is very expensive. You would almost certainly be better increasing the thickness of the concrete. If EMP is a worry you should have a manual switch to break the curcuit to the shelter.

      1. The steel plate will deflect the EMP, concrete will not unless you build in a Farraday cage, maybe.

        1. Everyone, There is a HUGE amount of “snake oil” being sold to the public in the form of EMP protection. Our EMP engineering consultant is a licensed Professional engineer with mil spec experience.

          He performs a demonstration showing how any hole in a faraday cage lets the EMP wave through and the cage is worthless.

          I am expressing even a pin hole can fully compromise the effectiveness unless planned as a wave guide.

          The Milspec standard is a fully seam welded 1/8″ plate steel enclosure, fully grounded. Less than that and we can describe all sorts of reasons why the enclosure will fail to protect for certain frequencies and amplitudes.

          As for hardening with steel. 5.56 855A1 ammo will punch through 3/8″ “mild” plate at 300 meters. Read it yourself in the NRA magazine this month.

          You’ll need HY80 or HY100 or at least AR500 steel to stop AP ammo with less than 1/2″ plating. Its great stuff, just not in everyone’s budget.

        2. your faraday emp man conning you. The holes mean nothing in a faraday. The cage works by capturing the emp. It hits the cage and follows the metal around to ground. The hole size is only dependent on the strength of what you are stopping and even then it is simple physics. It does not go through the holes.

          We tested many of these in military and ran many simulations. It actually does not take much to protect from an emp. As of right now, Texas is the only state that is actually hardening it’s grid against emp and solar storms. And it is not costing that much money. the cage will work just fine. You can take smaller items you want to protect and put inside metal trash can that is grounded. The stuff must be off the ground and not touching sides and it will be protected. it is not rocket science.

          solar storm can be different because you are talking not just an emp pulse but radiation. Different animal.

    2. Super simple any electromagnetic field or pulse which comes in contact with another field or Paul a bucking effect occurs which creates what’s known as the block wall effect and it’s kind of like canceling each other out except your feel the energized something as simple as some really thin wire screening around your room rcontainin electronic components or parts or devices could be simply energized with justa few volts from 6 12 your field would stay as to where the magnetic pulses or wave would dissapate over distance be cancelled out completely when coming in contact with your field which is more permanent FYI if all electronics are off fields and pulses are harmless to these items

      1. We found this not to be true. Unless protected being off does not protect certain circuitry from being fused. Solar storms can be worse. It is like an electric force being applied to the device and despite it being off the current still travels through the wires and fries processors and fuses wires etc. Being off has nothing to do with it. It is a myth, just like old time trucks and cars will run cus they don’t have computers… not true.. they still have batteries and alternators, wound coils that will be fused etc. true, it will be easier to get many of these up and running again where newer ones won’t run at all.

  7. I live in a mobile home in a remote area (off grid), but feel the need to provide some bullet resistance, as typical M. H. construction provides none. My solution is to construct a heavy duty skirting setting on a simple concrete foundation, placing 3/4″ X 18″ high density steel plate to the exterior above the floor level and vertically at the right side of window/door openings to allow for return fire (to the 6′ level). Then place 3/4″ furring strips above the steel (for attachment of vinyl siding). Next, I plan to apply Tyvek (or similar), then the siding. This makes it more permanent, but I own the property and have the flexibility to do this.

    It’s the only viable alternative I can come up with, but if anyone has other good suggestions – I’m open to them.


    Son of Liberty

      1. What about this new areocrete I think it’s called. I Suppose to Tornado debris resistant?

    1. outside the trailer, one could build up a new exterior wall with 8″ hollow concrete block, with the hollow cores filled with high strength grout. vertical #5 rebars at 24″ on center and for horizontals two #3 rebars in the joints at 16″ center will help hold this wall together for longevity, but that’s not a high impact reinforcing spec, the grout is doing most of the bullet stopping.

      This wall should be on a spread footing. I cannot know your soil type, but usually 16″ wide 10″ thick w/ two #5 rebars is typical for many basement walls.

      Keep this wall at least 1.5″ out from the trailer siding to prevent moisture from being trapped and rotting out the trailer walls.top the wall with a “c” channel to keep moisture out, especially if you live where it freezes; water freezing in the wall is s sure way for cracks to form.

      Paint the wall really well. a waterproofing concrete floor paint if possible.

      U- Block door and window lintels.

      1. Back in 1992 I was thinking this way with the addition I built. The basement is an 8 inch block wall with a few grouted columns with 5/8th inch rebar. Horizontal reinforcing and filled all other cells with clay, thinking insulation of some sort. But, that worked. In 22 years, no cracks in the blockwall.

    2. I live Louisville Kentucky and it gets kind of crazy around here these young kids seems like all of them want to be gangsters I have already had a pistol to my face twice in my own front yard I’m a veteran so I’m not allowed to carry firearms but I have negated that fact Ernie might seem silly and I don’t know how you feel about decorum but me personally I’ve just been hanging street signs in a single room in my trailer and big heavy pieces of aluminum that I’ve gathered from Power amplifiers I’ve seen what bullets do to aluminum street signs and for some reason they tend to ricochet very seldom do I ever see one that goes through strangely enough as it may seem I don’t know if that’ll do any help but it sure has brought me a little bit of comfort

      1. Please clarify. You’re a vet so you’re not allowed to carry firearms? First time I’ve heard that idea.

      2. its uncommon but not unheard of that vets get singled out. I live in Thurston County Washington (state) and the sheriff’s office mainly consisting of dishonorable fat and lazy county workers who deny all vets a CLP License to carry concealed or to purchase a firearm in a county controlled gun selling store. A vet can usually have their rights reinstated once they play nice and show the corrupt sheriff’s office they “are not a threat to public safety” and don’t have PTSD…I’m preparing to file a lawsuit as the county has continued to retaliate and take punitive actions, fines, civil lawsuit, harassment, etc. once I appealed their unlawful decisions…worst government agency in the country by far….

  8. There is a product called FRP Clad Foam. These composite wall panels consist of 1” thick polyisocyanurate foam core bonded to interior and exterior skins consisting of heavy fiberglass cloth/resin matrix bonded to marine grade plywood cores. Exterior finish is bright white gel-coat, interior in off-white resin coat or gel-coat(accepts paint). It is used to build high-end Fusion Splicing Trailers. They do not advertise that it will stop most hand gun rounds, but it does. I have seen the tests. You can get it in 4×8 sheets and it is pricy($100+ range).

    1. handguns vs.rifle rounds.

      Even a .44 magnum handgun is trying to approach 900 foot pounds of energy from a blunt projectile.

      9mm, .40 and .45acp are trying to get over 450 foot pounds with +p ammo.

      7.62 NATO “ball” rifle ammo puts out 2,600 foot pounds of energy from a very pointed “spitzer” bullet shape.

      7.62 Nato has more energy at 300 yards than 44 magnum point blank.

      Hornady.com has great ballistics tables to reference.

      apples to oranges.
      We don’t send the infantry to combat with a handgun for good reason.

      1. Sectional density is the ratio of an object’s mass to its cross-sectional area. It conveys how well an object’s mass is distributed (by its shape) to overcome resistance. For illustration, a needle can penetrate a target medium with less force than a coin of the same mass.

        A bullets sectional density is key to penetration. The higher the SD the better. The other important components are velocity and bullet composition.

        Foot Pounds of energy is not a good indicator of how well a bullet will penetrate.

        1. Yes. point well taken, and that is why I included “blunt projectile” for the 44 mag and “very pointy spitzer” for the 7.62.
          However Sectional density w/ good metallurgy alone w/o ft lbs of energy is not a valid claim, otherwise a steel blowgun dart would be the optimal projectile.
          You also mention velocity, velocity x mass equals energy. Two equal masses one at higher velocity, IS more ft lbs.

          Its a very complex topic, so I tried to stay simple with “blunt ” and “pointy” and I just deleted a much longer technical reply.

          But my main point however is, rifles vs. handguns is apples to oranges.

          We don’t harden Buildings to just stop handguns. Rifles are just too common to design for less.

  9. had this idea, which I think would only work for a new construction type thing..

    I suspect one does not necessarily want to announce to the neighbours that one is building a bullet proof house, however, one could build as per above suggestions, and just tell everyone

    “it’s tornado/hurricane proof”

  10. I don’t think it’s realistic to think you can stop bullets in almost any home in the USA, the cost and hassle is just too high for an event that may never happen.

    1. It may never happen, but it does, and it happened at my house a couple weeks ago. 9mm luger casings were found nearby on the street. 1 lodged in bedroom window ac, 3 dents in ac where others bounced.

  11. A true EMP Door with copper fingerleaf edging will cost between $30K and $50K.

    1. I used to work in buildings equipped with doors like you are describing. An airlock arrangement. TEMPEST. Cost an arm and a leg to build. Fake windows, etc. The doors were cheap in the scheme of things. Active protection for several thousand square feet of building against all RF types threats.

      Had to laugh when part of the building was downgraded. Saw folks carrying in boomboxes. Not a chance in hell of getting radio reception.

  12. I remember watching a Mythbusters episode where various calibre munitions were fired into a swimming pool and was intrigued by the results. How practical/costly would a liquid- or gel-based barier be for fixed defensive purposes?

    1. Now that your mentioning it, there is that science project that we made in science class when I went to school. Here is a short description “Scientists are using cornstarch to solve the mystery of a liquid that can instantaneously turn solid under the force of sudden impact—called a non-Newtonian liquid.” I heard that they were working on a version of this for personal body armor. We mixed cornstarch with water to a consistency of pancake batter. When it is subjected to impact it temporarily turns into a solid and back to a liquid again. The problem I could see with using that is the water may dry up or the cornstarch may separate from solution.
      I am just spit balling here but if you used oil instead of water, but that may slow the reaction down, but that would solve the drying out.
      This is cheap to experiment with. Mix some up, put it in a plastic 2 liter bottle, put the bottle up against a barrier so it doesn’t go flying, shoot the thing with the big guns and see if the bullet goes through the bottle or if it gets trapped in the bottle. From what I experienced in science class the bullet should get flattened in less than a quarter inch of the mixture and not make it past 1/2 inch. This is just a guess, but like I said, this is likely cheap stuff to experiment with. Make sure you take all precautions because I do not know what the reaction of the bullet will be when it hits the mixture, if it would deflect, or bounce back.
      If anyone has experimented shooting at this stuff, I would like to know the results as I don’t have anyplace I can go to experiment like that. I am sure my range wouldn’t allow me to experiment.

  13. hyzod polycarbonate is similar to plexiglass but restiant to small arms . I have seen a 9mm lodge in a piece about 3/8″ thick . comes in sheets I believe 4’x8′. try sandwiching gelcoat fiberglass cloth between the polycarbonate and plywood and run down to the range . let us all know how it does .

  14. The answer has been around since before the Romans. Rammed Earth construction. 18 inch compacted earth walls. cost of material? dirt cheap. labor intensive. buildings have 100+ year lifetimes. windows and doors still vulnerable of course. heavy timber beams easily supported with a metal or tile roof makes for fire proof construction.

    1. Geffrey the US military still uses a type of rammed earth construction, they are called collapsible Hesco barriers.

    2. if kept dry from rain, building have lifetimes in the 500 to 1000 year range.. look at the ones still standing in middle east and even churches from the 18th century in places as wet as the Philippines.

  15. Manufacture rectangular blocks of clay, dry them out and then fire them to a high temperature. These could then be used to build walls, in conjunction with cement. For more vulnerable exterior walls, I’d suggest doubling or even tripling the thickness. I posit that these high-density blocks would be able to stop all smallarms fire, and if doubled, possibly even rifle fire depending on the calibre. Here where I live we call them ‘bricks’.

    1. Maybe 4-inches of brick might be ok? but the usual 2-inch brick on houses won’t stop much.
      Yes, layers, probably 6-inches might work?

  16. During the boer war fast small forts were made of metal roofing sheets with loose gravel shoveled between them for a thick cheap wall effect They had lots of cheap labor and natural resources to use. A modified form of this could be adapted to the exterior of a home.

  17. There are a number of ways to stop a projectile. I think that a high strength concrete is the best. 10-12 inches minimum. (I have almost 14 inches thickness myself in my house) you could improve that With adding either 1 inch Natural stone plates (decorative purposes if someone ask) Hard granite has good stopping Power, but expensive. High strength brick wall is another solution. BUT bricks have very different mechanical strength. When it comes to insulation, you could choose a type that will absorb shrapnel, like some types of mineral wool, or high strength 2 Component PUR foam. If you feel the need for EMP protection, then choose one room in the house. Covering more is to expensive, and it is Nice to use Your cell phone indoors. There are conductive steel plates on the market. That is steel With added copper, but a standard aisi 304 stainless will work, in the right thickness. Just some thoughts

  18. 2×4 or 2×6 metal studs. 3/4″ plywood sheeting on the outsides. Back fill the walls with 3/4″ road gravel. Even the 2×4 wall easily stops a .300 Winchester Magnum. You can barely see where the round enters the plywood. The gravel actually works much better than concrete of the same thickness and it is a LOT less expensive. The 6″ panel will easily stop a .50BMG round. The magic is that the gravel saps the energy from the round by moving around a little as the bullet tries to travel through the wall. Concrete cannot do this. It has to fracture and crush to stop the bullet. Not so with gravel.

  19. It is important to use the metal studs because the gravel will fill the spaces inside of the C channels. With wooden studs it would be easy to shoot through the wood.

  20. No one wants them so they are free. Take phone books and pack them in the wall in such a manner to fill the voids. Packed paper does not burn.

  21. Go back and look at the clip on the sand experiment. 6 inches of sand stopped every bullet from penetrating. Metal studs, 3/4 in plywood, sand…good to go. Double up the studs and go extra deep.

    Some really great posts on this board, let’s keep them coming and let’s keep learning!

  22. How well do the logs used to build a log home stop the penetration of rifle bullets?

  23. Seems like it would be cheaper to just tear my house down and rebuild it, lol.

  24. Hi fellow humans, I am looking to provide portable easily erectable bullet proof protection in my existing home over the windows if needed. I am just looking to defend the front of my house with a system of items that can be attached to the inside of the house over the existing windows and walls if we need to. We tried ballistics tests today using AR-15 223 round; 30-06 round; 357mag round on a system which include 8 different combinations of plywood and 1/4″ PLATE STEEL; the results were challenging our resources. The AR-15 penetrated most combinations of 3/4″ plywood and steel plate combinations we tried. The most successful and effective was a combination of 1/2″ plywood/1/8″ steel plate/2 – 3/4″ plywood sheets/1/8″ steel plate. This stopped the AR15 223 round and the pistols; 357MAG; this did not stop the 30-06 180 grain round. Does anyone have suggestions of what to try and use to protect against the higher powered rifles like the 30-06 and 308? I know I can buy the expensive fiberglass composite panels for $1500 per 4’x 8′ panel. Is there a cheaper way to get there?? Thanks Steve

  25. As for us the house is hardened with fiberglass ballistic panel and has stone work as the external finish main floor. Daylight basement has 12 inch walls on 2 foot thick by 4 foot L footings double bar running long ways and up. Learn how to do this in Delta Alaska for our rich uncle. We don’t plan on staying in the house if big trouble comes but have fighting positions on the property. Two fighting bunkers near the front gate and two O.P.s in ambush locations. Easy to build with bags of ready mix timber roof covered with sand bags and dirt. Than just back fill and spray paint the yellow bags black or green that show. Use the bags like blocks and staged plus every 2 feet drive rebar down. One good rain storm and you have a solid wall of concrete.

  26. I haven’t read most of the prior comments, so I do not know if this will repeat.

    If you want a bullet proof home, build a “tilt-up,” just like one builds a modern warehouse.

    The exterior walls are all poured on the ground, lying flat, using whatever hardness rated concrete you wish, however thick you wish the wall to be. These are then tilted up upon a slab foundation and tied together with steel corners and butts…then spanned and held by engineered steel trusses..which can be designed as wished. The interior of the home is entirely devoid of any load bearing walls…so you may design the interior as you wish, changing it as you wish at any time.

    Now, you may wish to design your entrances and windows to enhance them to the degree you desire, including the strategic placement of landscaping berms and baffled entrance ways.

    Such a structure can be created to be beautiful and hide most of is purposeful hardness to attack.

    Otherwise, harden your bedroom exterior walls and used embassy glass in the fire escape windows.

  27. would have thought someone might come out with a line of siding and of shingles/roofing cover which might do the trick or come close?

    as an urban home owner, I see no “easy” way to bullet proof aesthetically. Now, I don’t really at all want to be slapping up pieces of concrete or plywood, and darn sure the community would be complaining to the city, (so might I ..)..
    and, actually do not need new siding..but, there might come a day

    on another approach (no not doing this either), but wondering if those earthbag houses (bags of dirt packed tight), would do a fair job of being bullet proof?

    1. Jane Fox
      The earthbags or cob construction would be excellent, kinda cool designs can be made too…

      1. Kulafarmer ..good to know. As I say, am not in the market for this, but may be some who are. You’re right, I too have seen some amazing designs..

    2. Actually there are several references in the comments above regarding alternatives. Though expensive.

  28. Ken, et al.,
    Would using 1/2 inch cement backer board on the street facing exterior walls help in providing some bullet resistance for most common handgun ammunition (e.g. .380, 9mm, .357, .38, 10mm, .45) vs. double wall construction using common thickness drywall and exterior siding? Do you think it would be cost effective?

  29. Thanks for the article Ken.

    It makes me wonder why the city of Boulder, CO was exploring this option.

    Do the city inhabitants fear the errant bullet from a hunter in pursuit of Bambi at the edges of town? ( hence the use of a 270.)

    In South Central Los Angeles, a majority of the shootings that took place were from shotgun and pistol rounds with the serious people bringing out AK’s because they are low in cost for both ammo and weapons. ( many of these shooting were also empty-the-magazine and drop before you run/drive away.)

    Different problems within different areas. My solution? I moved away and did a job where I was not working with crime scenes or the perpetrators anymore.

    The cost of building such a property would be cost prohibitive for me and a majority of the cost would be in the foundation to support such heavy walls. I did not see Infantry Architect mention the building of Hescos as these were used overseas in rocky areas. I must admit, they are not at all visually appealing. (Columns of rocks piled within a cylinder of hardware cloth or wire.)

    Other than buildings being breached by a suicide bomber, the Southern Cal phenomena seems to be: driving a stolen car or truck through the front door in order to do the breaching.

    One local retiree of Southern CA law enforcement went with asian inspired architecture and built up several “privacy screens” blocking direct view of his house, windows and front door from the street. The privacy screens are made of wood, they go to the ground and his wife painted bucolic scenes on them. so they blend into the garden around the front yard. The driveway goes in beside the house and windows within the house view the driveway that is gated. The privacy screens also stop handgun bullets. filled with gravel.

    Then there are the neighbors beside you…substance abuse problems? undiagnosed psych issues?

    I think I will try to join Dennis on his mountain…I bring rolls of clean toilet paper.

    1. Calirefugee — Golly
      “I think I will try to join Dennis on his mountain…I bring rolls of clean toilet paper”..
      one hopes you are bringing “clean” toilet paper..grin..
      otherwise, methinks it is “compost”..

      all good

      maybe we can all run up to Dennis on his mountain..grin

      1. This is the article that first brought me here years ago. It was some time later I started posting.

        Bullets are interesting creatures. Normally excruciating velocity penetrates armor. Or a special projectile, or massive amounts of energy at low velocity.

        I like to shoot stuff. Trees. Cars. Pick something.

        You are essentially trying to dissipate energy. The easiest way to do it is to buy time. Slow it down through a viscous fluid. Or something like it such as sand or loose stone.

        The next easiest way is to fragment it into smaller and more manageable pieces of energy.

        The next easiest is to have something that has a greater yield modulus.

        I have found that a 2×6 steel studded wall filled with crushed 3/4″ no fines stone to be effective from monolithic 12 gauge magnum slugs to 4000fps 4000ftlb 300 Winchester Magnum.

        If you want thinner then you need some hardened steel (I used 1/4″ AR500) to be the final piece to stop the projectiles tested.

        The stone is nice because it is self-healing. When stones are hit and shattered the bullet fragments. Then hits other stones. Rinse, repeat. Any stones destroyed are replaced by gravity.

        To minimize stone leakage as the sheathing fails I found EPDM rubber roofing to be an excellent gasket. I air nail with roofing nails to the outside of the sheathing.

        I found it takes about 30″ of dirt and 30″ of wood to stop bullets. I found concrete blocks are easily destroyed with multiple hits.

        What I ended up building as a structure with two walls. Outside going in:
        EPDM rubber roofing
        7/16 CDX
        2×6 steel studs with 3/4″ crushed gravel between
        1/4″ AR500 for the first 5′ from the floor then 1/4″ plywood for the remaining to the ceiling.
        Standard 2×4 and normal R13 insulation between
        5/8 Type X drywall

  30. Lake City. 556 green tip LAP, at 50yds, will NOT penetrate a simple cinder block wall. Neither will FMG 55 grain, nor hollow point. Plywood, 3 to 3 1/2 in.

    308, 165 grain FMG, 25yds, will penetrate the first block, but will not penetrate the 2nd block. Plywood, 4 1/2in

    6.5 Creedmore, 25yds,140 grain core loc, same results as the 308 round. Plywood 4 in

    338 Lapua, 250 grain, 25yds, will penetrate 1 1/2 blocks. Plywood, 4 1/2 in

    9mm, 40cal, 45acp, standard ammo, 10yds, penetrated just 1 side, no damage to other side. On 3/4 in plywood. penetrated to the 3rd sheet, 2 1/4 in

    1. SMG

      Is the cinder block wall assuming cinder block cells are concrete filled?

      1. Farmgirl

        Not filled. Set up on end, 3 in a row, with a bullet gel back stop, plus a dirt bank 5 yds behind shooting range. All ammo is factory store bought, no reloads.

  31. Stand my Ground

    Ok, thanks. Our walkout basement is cinderblock construction, concrete filled w/ rebar. Most below ground level, with interior basement rooms the same. So we’re good there. Weak spots are windows and walk-out framed wall. (And the ceiling above, should there be an upper level breach…next item to solve) I’m thinking I’ll get next year’s greenhouse soil, stacked at least 4 feet high laying flat. Bags I get are commercial size, wide and heavy, somewhat compressed but not like bricks; not as good as sand. I’ll have to sit with that some more. Thank you for the info.

  32. For a multi level dwelling, I’m thinking about how to create cover for fire from above (or below). Ultimate goal is not to let the bad guys in the house in the first place, but in the unthinkable event that should happen, it is something I need to address. As a civilian, it took me a while to break the concealment is cover mindset; trying to do a good assessment and saw this above/below vulnerability. Anybody have ideas about addressing that? Thanks.

  33. .50 Cal ammo boxes filled with sand are portable, easy to handle, stackable and will provide reinforcement to existing walls. Purchased in bulk they are affordable and have a multitude of other uses.

  34. You have plenty of money and want to build a house that is resistant to earthquakes, bombs, and an F-5 tornado? Look up the Pensmore Mansion/Chateau/Castle in the Missouri Ozarks. Its outer walls are twelve inches thick, made of concrete with Helix reinforcement fiber. It’s a bit larger than I would care to clean, at 72,000 square feet. Still, the Helix/concrete mix sounds like one way to consider building whenever I win the lottery and build my dream home.

    1. Wendy

      That is one interesting looking place! So the guy who built it is ex-Army Intelligence, ex-CIA astrophysicist. Self-sustaining, indestructible and in the middle of nowhere. Even his own herd of wild exotic pigs roaming the property. No wonder conspiracy theories about it abound.

      Maybe you could afford a small hut made of the stuff? :-)

  35. I’m thinking I could just bake up some hard tack in the form of bricks and line the wall…. It can double as survival food LOL!!!!

  36. I’m thinking I could just bake up some hard tack in the form of bricks and line the wall…. It can double as survival food LOL!!!!

  37. Retrofitting is always going to be the expensive option and usually not a satisfactory one. New construction can have at least have a safe room(s) built in. Old construction has a lot of maybes built in from structural support to aesthetics.

    Earth sheltered is an (relatively) inexpensive way to build a resistant structure that also protects from weather events as well if your area can support it (no low water table or near surface bed rock etc).

  38. What about using cordwood? Not great in a main living area, but for a walk-out basement wall? Normally, I wouldn’t bring it inside in any quantity because bugs. Good mass, though, stacked properly and away from the wall a bit so it doesn’t cause moisture issues in the drywall.

    For the overhead breach, about the only thing I have so far is something to get under, like an extra thick tool bench. Aargh! Don’t have it yet. Will keep thinking on it.

  39. Found a website that sells sandbags, including military grade. Search for the sandbagstore. A makeshift option, if your structure can bear the load, and it doesn’t need to match your decor, Lol.

    1. Forgot to mention, Veteran owned, Made in USA and free shipping. There are even camo sand bags, if you’re setting up a ‘play area’ outside.

    2. Been sewing my own as needed, I use that heavy woven black weed mat, it lasts wayyyy longer and does not degrade in the sun. Plus i can make them big, made some that i pick up with the forks on my tractor, stacking them for retaining some dirt. Been cutting it about 12’6”+/-, makes a 4’ diameterish bag or if semi square about 3’is

  40. Bullet proof your home by creating planters outside, which allow one to pile stone and sand up to at least the height of your window sills. Then face your exterior with stone, or brick, to cover higher portions in key areas. Modify low windows to raise the height to allow better bullet resistance and create standing breastworks. Create dirt mounds to block line of sight in your landscaping and build stone walls to add cover at a distance.

    1. Ision — I think that is a good suggestion, planters, etc..Even in an urban area, one can figure on some kind of planters, which would cause neighbors to call the bylaw on you

      1. Ison.sorry, that should have read “would NOT cause the neighbors to call bylaw”

        (need more coffee…)

  41. To go with my above about bulletproofing…

    You can strategically place boulders or flagstones on end as barriers for cars. A row of gapped 20″ boulder will slow down a dumptruck and stop a passenger car.

    At my employer we have 8 ton flagstones partially buried in the ground that are staggered. They look decorative but that is not their intention. It stops pretty much all non-tracked vehicles.

      1. Kulafarmer, no but one of Ronnie Barrett’s M82 50 cal rifles being operated by a home owner would stop that Cat 960 loader. Don’t forget, there are 1000’s of those rifles in private hands in this country along with millions of rounds of API to feed it.

  42. What about this new areocrete stuff I think it’s called. It supposed to stop tornado debris?

  43. My comments refer to many of the posts here and may offer some assorted ideas.

    During the early years of WW II, when armor plating in England was very scarce, the boffins experimented with panels of asphalt to protect the wheel house of the new corvettes from shell splinters. I have only found two references to it and no specifics. Certainly, it MIGHT work on a budget.

    IF you have the option, the best place to defend your home is from the outside where you are not trapped. Secure locations of many kinds, located 50-100 yards away are best.

    For most rural homes, your most vulnerable structure is not your home but your propane tank. If you have the option, bury it. If not, build a gabion wall around it.

    That gabion wall is also your best defense for your home. The baskets are inexpensive and the rocks and rubble are free. Also, they look nice and don’t advertise the fact that they are defensive structures. A lot of homes have a decorative fence around their front yards. A 2′ thick wall of large creek stones nested in sand or dirt will stop .30-06 AP. The rubble is actually much better than concrete because the movement of the stones within the sand/dirt matrix absorbs some of the shock that fractures the concrete. Build your wall 3′ high and top it with planter boxes for flowers or veggies. Remember, rocks are where you find them daily and they are cheap.

    One of the best EMP solutions is a grounded all-metal-enclosed filing cabinet or metal storage cabinet. You can put a lot of sensitive stuff in these but, remember, that they must be insulated from touching any of the metal. Wrapping paper is good, bubble wrap is better.

    1. – When I was stationed in Germany, in my travels around, I came across some WWII construction that included upright panels of Asphalt that still had .50 slugs still imbedded in them. It looks like to me they worked, although I could not tell you the range or circumstances they were fired at or under.
      – Papa S.

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