Fasteners for Concrete and Brick

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Fasteners for Concrete and Brick

Advice for contractors installing rigid foam or furring strips to walls made of concrete, CMUs, or bricks

Posted on Jun 29 2018 by Martin Holladay
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Builders who install rigid foam insulation need to know what type of fasteners to use for a variety of substrates. One challenging situation involves installing rigid foam or furring strips over concrete, as might happen when rigid foam is installed on the interior of a basement wall. But even builders who are familiar with fastening methods for concrete might wonder if the same techniques are appropriate for brick walls.

In this article, I’ll try to provide advice on the best mechanical fasteners for concrete, brick, or CMUConcrete masonry unit. Precast concrete block used to build walls. CMUs have hollow cores that can be filled with concrete onsite for additional reinforcement. The use of stronger, more lightweight types of concrete such as autoclaved aerated concrete (AAC) is becoming increasingly popular in CMU manufacture. (concrete masonry unit) walls. I’ll consider a variety of scenarios, including the attachment of furring strips directly to the wall, the attachment of rigid foam without furring strips, and the attachment of furring strips through a layer of rigid foam. I’ll also look at the best fasteners for OSB or plywood subfloor panels when the subfloor is installed over continuous rigid foam above a basement slab.

Types of fasteners

There are two basic types of fasteners for concrete and masonry:

  • The first category of fasteners requires a predrilled hole. Examples of this type of fastener include concrete screws (for example, Tapcons), wedge anchors, hammer-set fasteners (for example, Red Head Hammer-Set Nail Drive Concrete Anchors), certain concrete nails (for example, Trufast Tru-Grip fluted concrete nails), and plastic fasteners for holding rigid foam to a concrete wall (for example, Styro Industries Tapit fasteners, Rodenhouse Plasti-Grip PMF fasteners, or Hilti IDP anchors).
  • The second category of fasteners does not require a predrilled hole. Examples of this type of fastener include powder-actuated fasteners, fasteners driven by gas-actuated tools (that is, tools with an internal-combustion engine that uses disposable gas cartridges), and old-fashioned concrete nails.

Drilling a hole in concrete

If you’re using a fastener that requires a pre-drilled hole, you’ll need a hammer drill with a depth stop. (Although it’s possible to drill holes in concrete with an ordinary electric drill, the work is far faster with a hammer drill.) Use a high-quality bit designed for concrete.

In most cases, the hole needs to be 1/2 inch deeper than the fastener will penetrate. Once the hole has been drilled, use a turkey baster or a baby’s ear syringe (available at drug stores) to blow the dust out of the hole. It’s also possible to vacuum out the dust or to blow it out with an air compressor.

If you’re fastening furring strips or rigid foam (or both) to a concrete wall, you should be able to hold the material against the wall and drill through all of the layers to reach the concrete below. Just make sure that you’ve bought a bit that’s long enough.

If your drill bit hits rebar or a chunk of very hard aggregate (gravel), the bit may slow down or stop. If that happens, it’s usually easier to drill in a new location than it is to try to fight these difficult materials.

Concrete screws

Concrete screws are versatile enough to be used for most tasks involving furring strips or rigid foam attachment.

The original brand of concrete screw is the Tapcon, which is manufactured by a company called in Itasca, Illinois (see Image #2, below). Tapcon screws are available in several versions (including stainless steel) in a variety of lengths up to 5 inches. Concrete screws can be used for concrete walls, CMU walls, or brick walls.

While Tapcon screws work, some installers complain that they are brittle and prone to breakage. By now, several competitors have entered the field. One well-regarded manufacturer, GRK Fasteners, makes a tough concrete screw called the . Several GBAGreenBuildingAdvisor.com readers report that these Caliburn concrete screws are less likely to snap than Tapcons.

Burke Stoller posted the following comment on GBA: “I suggest getting something better than Tapcons. They are a pretty poor quality fastener. They tend to snap off, or else the threads strip before they really suck down. For a fantastic fastener into concrete, use GRK Caliburn concrete screws. Or, Simpson Titen concrete screws are not bad, as long as you get the ¼-inch diameter ones. Those GRKs are the Cadillac option though; you can even back them out and reinsert them a few times and the threads still stay sharp!”

What if you need a very long concrete screw? You might consider buying the , a concrete screw that is available in several lengths up to 24 inches.

If you are installing rigid foam with concrete screws, you’ll need plastic washers. These washers (generally known as “foam fastener washers”) are produced by several manufacturers, and are readily available at outlets like Home Depot or Menard’s.

Not quite a concrete screw

Trufast makes long screws (, available in lengths up to 18 inches) that work on CMU walls, but not poured concrete.

Trufast also makes a special concrete nail () that is used to fasten thick SIP panels or nailbase to concrete. This type of concrete nail requires a predrilled hole. Trufast Tru-Grip fluted concrete nails are available in lengths up to 12 inches.

Hammer-set fasteners

If you are attaching something relatively thin (like furring strips) to a concrete, CMU, or brick wall — without any rigid foam — you might want to use hammer-set fasteners.

Like concrete screws, hammer-set fasteners require a predrilled hole. Hammer-set fasteners are surrounded by an expandable sleeve. Once the fastener is inserted into the drilled hole, the installer drives the fastener home with an ordinary hammer, and the sleeve expands.

One popular brand of hammer-set fasteners is . The maximum available length of these fasteners is 2 inches, so they generally aren’t used for rigid foam. (Other brands of hammer-set fasteners are available in lengths up to 3 inches; for more information on these fasteners, see Comment #4 by Kohta Ueno, below.)

Manufacturers also offer a variety of fasteners similar to hammer-set fasteners; some require a hammer, while others require a screwdriver. Depending on the manufacturer, these fasteners may be called wedge anchors, sleeve anchors, plastic splay anchors, or metal shield anchors. Each type of fastener is designed for a different purpose, so study the installation instructions before use.

Plastic fasteners for holding rigid foam to a concrete wall

In most cases, rigid foam needs to be protected with a layer of 1/2-inch drywall for fire safety. (Confusingly, building codes refer to this layer of drywall as a “thermal barrier.”) However, a few brands of polyisocyanurate, including Thermax, can be left exposed (without any drywall protection) in a crawlspace. Readers should check with their local building department to determine how this section of the code is interpreted by local authorities.

If you are installing rigid foam that will remain exposed, you may want to attach the rigid foam with plastic fasteners designed for this purpose (see Image #3, below). These umbrella-shaped fasteners require pre-drilled holes.

The three most common brands are:

  • , which are available up to 4 inches long.
  • , which work for rigid foam up to 5 inches thick.
  • , which work for rigid foam up to 4.75 inches thick.

Marc Rosenbaum wrote a GBA blog about the use of this type of fastener; his blog was titled “Basement Insulation — Part 2.”

Power-actuated fasteners

If you want to avoid the hassle of drilling holes in concrete, you might want to consider using power-actuated fasteners. There are now three types of power-actuated fastening tools. The original power-actuated fastener is the powder-actuated fastener — note the “d” in “powder” — driven by a tool that operates like a firearm. It it uses cartridges filled with gunpowder to drive a piston that drives a fastener.

There are two newer types of power-actuated fastening tools: the gas-actuated fastening tool (driven by an internal combustion engine that requires a fuel cartridge) and the battery-actuated fastening tool (driven by a powerful spring that is wound by an electric motor). Collectively, these three types of tools — powder-actuated, gas-actuated, and battery-actuated — are referred to as power-actuated fasteners.

Powder-actuated tools are the most versatile of the three tool types. If you’re interested in a powder-actuated tool that is specifically designed to attach rigid foam to a concrete wall, you’ll end up paying between $700 and $1,400.

For example, the powder-actuated tool is designed to work with the Hilti X-IE 6 plastic fasteners for rigid foam attachment to concrete or CMU walls. This system is fast and easy. The only drawback is cost; the Hilti DX 5-IE tool costs about $1,000.

Ramset promotes a gas-actuated tool, the , for fastening rigid foam to concrete or CMU walls. The Ramset system is designed to use Ramset IFC fasteners, which have a large (2 3/8 inch diameter) plastic head, and are available for rigid foam up to 6 inches thick. The Ramset TFIF-3 tool costs $749. A fuel pack capable of driving 1,000 fasteners costs about $24.

What if you just need a tool that can be used to install 1x4 or 2x4 furring strips directly to a concrete wall? In that case, you probably just want to buy an inexpensive powder-actuated fastener tool for about $300.

Fastening to bricks

Powder-actuated fasteners can’t be used on brick walls, because the bullet-like velocity of the fastener ends up shattering the brick. If you’re attaching something to a brick wall, you need to predrill a hole. Once the hole is drilled, use a concrete screw or hammer-set fastener.

If you can see what you are doing — in other words, if the brick-and-mortar wall isn’t hidden by a layer of rigid foam — try to drill the holes into a brick, not a mortar joint.

What about the use of adhesives?

While furring strips always require the use of mechanical fasteners, rigid foam can sometimes be attached to a wall with construction adhesive alone. Remember to select an adhesive that is foam-compatible, and set up a system (for example, scraps of plywood and diagonal braces) to apply continuous pressure to the rigid foam until the adhesive sets.

No matter what type of material you are fastening to a concrete, CMU, or brick wall, using an adhesive in addition to mechanical fasteners can provide a little bit of extra holding power that may give the installer some additional peace of mind.

A conversation with Robert Dettman

I recently had a phone conversation with Robert Dettman, a manager at Hilti, which manufactures fasteners and power-actuated fastener tools. I spoke with him on the topic of fastening various materials to concrete and masonry walls.

I asked Dettman what type of fastener system he would recommend for attaching 1x4 furring strips to a concrete wall. He answered, “Commonly, for either concrete wall or a CMU wall, I’d advise the use of power-actuated fasteners. If you choose a very basic tool — for example, the — you can get the tool for $299. The DX2 automatically advances the strip with the powder charges, but you have to manually load the pin each time you fire it.”

What about brick and mortar walls? Dettman answered, “If you are attaching mechanically to a brick wall, the system you would use most often would be a small diameter screw anchor or a nail-in anchor. All of these anchors require a small predrilled hole. Going into brick, you have to use a mechanical fastener. You can’t use a powder-actuated fastener. It’s best to stay away from the mortar joint. There are a couple of big problems when going into brick, because the hardness or softness of the bricks can vary. Sometimes the fastener can’t grasp the brick enough. One way to solve this problem is to use what we call a ‘matched-tolerance bit’ for brick — it’s a drill bit with a slightly smaller diameter. Or you can use something like a plastic splay anchor.”

What about fastening 2x4 furring strips to a concrete wall? “You can’t use a gas-actuated or a battery-actuated tool for 2x4s, because they don’t have enough power,” Dettman said. “You need a powder-actuated tool.”

I asked Dettman whether you can use a powder-actuated fastener to attach a 1x4 furring strip over rigid foam to a concrete wall, or whether the two layers had to be attached separately. “You can do it all in one shot,” said Dettman. “A powder-actuated fastener will go through the wood and foam into the concrete. I would recommend using a powder-actuated fastener with a pre-mounted steel washer, so the pin doesn’t go through the furring strip. We offer the pins both ways — without a washer, or with a pre-mounted washer. If the pin gets too long, though, it won’t work. I would say that around 3 inches of foam plus a furring strip is as thick as you can do with this method.”

I asked Dettman what type of fastener he recommended for attaching plywood or OSB subflooring to a concrete slab when there is a continuous horizontal layer of rigid foam between the subflooring and the concrete slab. He answered, “All the mechanical fasteners are very appropriate. You can use concrete screws or a powder-actuated fastener with a steel washer.” I pointed out that if you are installing subflooring, you can’t have a proud fastener, and Dettman admitted that maybe the washer wasn’t a good idea. “You could drive the pin without the washer,” he said. “With most tools, you can dial up or dial down the power, to make sure the pin ends up where you want it.”

Comments from GBA readers

GBA readers have posted advice on fasteners for concrete and masonry. A reader who uses the screen name Yupster advises, “Pre-drill a hole, insert a piece (or pieces) of copper wire, and hammer in an spiral nail. That’s a classic method of securing to concrete, and cheap, too. It would provide good shear strength and when it’s done right, they are very difficult to pull out. I’ve used many Tapcons; they work fantastic. You have to be careful not to overdrive them and you have to make sure you drill the hole about 1/2 inch deeper than the length of the screw. Do it right and they are the bee’s knees. Maybe consider adding adhesives to your list of concrete connectors?”

Malcolm Taylor wrote, “I’d suggest adhesive when possible, especially when trying to attach to soft porous masonry. PL Premium Fast Grab is my favorite. After too many sheared-off heads I’ve given up on Tapcons. I find that Caliburn screws from GRK Fasteners are more robust for hard concrete.”

A reader named Kevin (a.k.a. KJMass1) wrote, “I’ve done two home projects recently that involved attaching either 2x4s on to a brick/mortar-parged wall, or a 2x6 flat on bricks as a sill to mount to. I used a hammer drill for the pilot hole and hammer-set fasteners. The unevenness of my 1940s wall caused me a little trouble getting a couple of them to bite well (but manageable), but on a flat concrete foundation wall they would work great. Definitely get long ones as you want as much as possible in the wall. I also found it helpful to remove the nail from the sleeve so you can get the sleeve in place before hammering it home as sometimes the nail would start to set before the sleeve was fully embedded. I haven’t had too much luck with Tapcons other than extra-large screws to hang my pictures in my plaster walls. I’m sure they have a place, though.”

Rick Van Handel wrote, “Whether it’s fastening sole plates, ledgers, or strapping, I have very little faith in Tapcons. Even with a hole drilled to their specification, about 1 in 4 tends to twist the head off before they are fully set. This is in installation to solid concrete, so block might work OK. I have had good success with the hammer-in split-pin anchors. If you drill a hole you can’t screw it up. They grab hard enough to suck in a warped board, and you can drive them flush into framing lumber without countersinking. I also like the hammer-set anchors, but I don’t think they are as strong in shear and the heads won’t sit flush without countersinking.”

Lukas Schwartz advised, “When it really matters I use GRK concrete screws. Vacuuming out the dust before driving in the screw helps. Tapcons I use only when little strength is required. Decking screws work too, if the pilot hole is sized right.”

Martin Holladay’s previous blog: “Using a Dimple Mat to Keep a Basement Wall Dry.”



Image Credits:

  1. Image #1: Building Science Corporation
  2. Image #2: ITW Buildex
  3. Image #3: Marc Rosenbaum

1.
Jul 4, 2018 2:35 PM ET

mason jar lids or plywood as washers
by user-7062640

In the interior of my walkout basement I've been using foil faced polyiso, either 2 or 4 inches (2" below grade, 4" in walls above grade). Polyiso seems favorable from a greenhouse gas standpoint, has a high R per inch, and meets the flame and smoke rating requirements here for basement walls, so I can avoid covering it with drywall. I've been using either 3.5 or 6 inch tapcon screws because they're easy to find. Where I want to hang tools or protect the foil from wear, I'm using a plywood sheet essentially as the washer. In areas where that's not necessary, I used a mason jar lid plus a wide washer. These distribute the strength of the screw and are holding the polyiso sheets very tight. Here's a picture plus detail of both--plywood where the tools are, and just mason jar lids behind the built-in cabinet.
-Shawn Salias

whole assembly.JPG washer detail.JPG plywood detail.JPG


2.
Jul 4, 2018 9:42 PM ET

Shawn
by Malcolm Taylor

If you run out of mason jar lids, you can buy cap washers at most big box stores. They are about 20 bucks for 500.


3.
Jul 5, 2018 7:15 AM ET

Edited Jul 5, 2018 7:52 AM ET.

Response to Shawn (Comment #1)
by Martin Holladay

Shawn,
You wrote, "Polyiso ... meets the flame and smoke rating requirements here for basement walls."

You may be accurately reporting the interpretation of your local code official. But most code officials won't allow foil-faced polysio to be left exposed, because it's a fire hazard. Rigid foam needs to be protected by a layer of 1/2-inch drywall.

The exception is a brand of polyiso called Thermax -- a special type of polyiso that has passed fire safety tests. (I think there is at least one other brand of polyiso that has successfully completed Thermax-type testing and approval, but I forget its name.)

So most common brands of polyso need to be protected with drywall.

Malcolm makes a good point. Foam fastener washers (which I mentioned in my article) cost about 4 cents apiece, whereas mason jar lids cost 18 cents each at WalMart.

Of course, if you are talking about used lids, they're free (assuming you do a lot of canning, and you've been saving your used lids). Remember, though, there there may be a better way to use these lids. If you open your mason jars carefully, the lids can be re-used for your next canning job. That's what I do.


4.
Jul 5, 2018 9:08 AM ET

Hammer-Set Fastener Options
by Kohta Ueno

Like concrete screws, hammer-set fasteners require a predrilled hole. Hammer-set fasteners are surrounded by an expandable sleeve. Once the fastener is inserted into the drilled hole, the installer drives the fastener home with an ordinary hammer, and the sleeve expands.

One popular brand of hammer-set fasteners is Red Head. The maximum available length of these fasteners is 2 inches, so they generally aren’t used for rigid foam.

As an FYI, 3 inch lead and plastic tap-in/hammer in anchors are available; I have successfully used them to install 2 inches of foam to my basement walls. I used plastic washers (had to be drilled out for the 1/4" diameter fastener) to prevent pull-through of the fastener. The hammer-in fasteners had intermittent problems expanding due to the "bounce" of hammering through foam; I found that I had to "pre-expand" the fastener slightly to get it to work.

All this being said--if I had to do this all over, I'd just buy the Rodenhouse fasteners.

Mushroom Head Nail In Anchor Nylon 1/4 x 3 (Box of 100) weight 2.25 Lbs

1 3/4" Foam Fastener Washers, 100 Count

Also, for reference, this is how Joe's dad solved the problem:

BSI-065: But I Was So Much Younger Then (I'm So Much Older Than That Now)*

IMG_8145 Bsmt Insulation.JPG IMG_8152(1).JPG IMG_8861.JPG


5.
Jul 5, 2018 9:19 AM ET

Response to Kohta Ueno
by Martin Holladay

Kohta,
Thanks for sharing your tips and experience.

If GBA readers are curious about Joe Lstiburek's father's home-brew masonry fastener, the relevant information is reproduced below.

Joe Lstiburek wrote:

"How to attach 8 inches of foam insulation to the outside of a block wall? ... Time to go see Dad. ... After about an hour he got up without saying a thing and I followed him to the car and we drove to Canadian Tire. He got a long masonry drill bit, some gutter nails, a bunch of really big washers and some lead plugs. He sketched out the solution on a pad of paper. ... Worked like a charm.

"[Caption to image] Dad’s Fastener - Gutter nails, a bunch of really big washers and some lead plugs. Put the nail through the washer. Push the lead plug onto the end of the nail. Lean the rigid foam against a masonry wall. Drill through the foam with a 5/8-inch diameter long masonry bit 1-inch into the masonry wall. Pull the bit out of the opening. Insert the fastener through the foam 'pilot' hole so the lead plug engages the hole in the masonry. Use a mallet to hammer the fastener home."

.

Homebrew fastener for masonry walls - Lstiburek.jpg


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