A Subfloor for Your Basement

Engineered flooring shown over a basement subfloor. STEVE MAXWELL/POSTMEDIA NETWORK

If you’re finishing your basement, whether it be for it to serve as an exercise room, play area for the kids, or simply as a means of getting the TV downstairs, all in an attempt to create a more peaceful living atmosphere on the main level, you’re going to need flooring.

Options?

Other than basements, or essentially below-grade (ground-level) installments, being off limits to solid hardwood flooring and some engineered hardwoods, mostly any type of flooring can be installed in a basement. However, your first brainstorming efforts regarding the flooring should be dedicated to the underlay materials, or basically what’s going to be installed under your preferred flooring material.

Because concrete basement floors are naturally cold and damp (which is why solid wood products don’t do so well when installed overtop) homeowners with eight or more feet of floor-to-ceiling headroom may want to consider a dimpled membrane/ridged insulation/plywood combination of underlay products.

Essentially, everybody benefits from a warm floor.

If you’re not sure about the warmth benefits of ridged insulation, or question the power of its reflective energy, visit your local building supply centre and ask to see a sheet of ridged pink insulation, commonly referred to as code-board, or Johns Manville’s (JM) ridged polyiso panel, often called RX board. Request that the sales clerk lay the sheet down on the floor.

If for this test case the panel in question is the JM board (which has a slightly superior R-factor over its competition due to an aluminum coating on one side), ask the reflective aluminum side be facing up. Next, calmly remove your shoes, remain on what’s most likely a concrete or tile floor for a few moments, then, gently step onto the sheet. If your wearing socks on your feet, no problem, the fact that sock material does have some insulating properties will only slightly skew the test. For the purpose of demonstration, bare feet would actually serve best, but unless you’re wearing sandals, you may not want to be the designate of a call to security regarding a disrobing occurring in aisle three.

While in the act of stepping onto the sheet, the salesperson may motion towards you in a somewhat guarded manner, offering a hesitant, “I’m— I’m sorry ma’am, but we don’t really allow our customers to walk on…” However, the clerk’s urgency will be to no avail, because within seconds the reflective and insulating properties of the ridged foam will be warming the bottoms of your feet. Remain on the sheet for about 30 seconds.

By this point, the junior sales clerk will have most probably left the scene to seek the aid of management, or possibly the in-store security. Either way, you’ve now got about 45 seconds to complete the test, because in 60 seconds you’re likely to be escorted off the premises.

So, step back off the sheet and stand on the concrete floor (still in your socks or bare feet) for about 10 seconds, thereby experiencing that cool, damp feeling again, then, step back onto the sheet for another 10 seconds and, ahh— feel that warm, comfortable sensation of heat returning to your body.

With test trial “ridged warmth” now complete and proven successful, you’ll have about 25 seconds to pull on your socks and tie your shoes, then hastily make your way over to plumbing, or the nearest unrelated sales area.

This best scenario basement subfloor option would have you first laying out a roll of Dorken’s Delta basement floor barrier (or an equivalent) directly on your concrete floor, dimpled side facing the concrete. Next, place a layer of either three-quarter-inch (R-5) or one-inch (R6.5) JM ridged polyiso overtop, using a roll of red sheeting tape to hold the sheets together.

Then, install sheets of either five-eights-inch or three-quarter-inch tongue-and-groove plywood, or OSB (oriented strand board) overtop. Use tapered tapcon screws to secure the plywood, which must penetrate the concrete by at least three quarters of an inch.

Next week, more on basement floors.

Good building.

As published by the Standard-Freeholder