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 CMU (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:
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…