Finishing the Basement

In the event I ever get around to becoming a university professor, I’ve got my first research topic chosen: Basements, Potatoes and the Canadian Psyche. It springs from a theory I have, one that I’ll test after my seven-figure research grant comes in from the Ministry of Architecture and Root Crops.

I contend that Canadians have basements today because of a throw-back to the era when each household required a frost-proof root cellar for winter-stored potatoes, carrots and turnips. Look to warmer parts of the globe and you don’t often find basements under anything. And that fact has something to teach us Canadians about basement renovations.

It doesn’t matter that most of us can now buy potatoes any day of the year. Tradition has a long arm. For most Canadians, a house is not quite a home without a basement. So in one sense, even modern, finished basements are still used to store potatoes. Nowadays, any worthwhile basement potato bin needs wall-to-wall carpeting, a big-screen TV, and a plush couch for the two-legged potatoes that lounge in front of it.

If you’re planning to finish your basement, then it’s always wise to keep in mind what you’re really up against: the conversion of a hole in the ground into a warm, dry, bright living space. And this fact exerts more influence on the nuts-and-bolts of a successful basement reno than anything else.

Foot-Friendly Basement Floor

A reliably-dry space is the essential starting point for any basement finishing project. Don’t even think about starting without that. But even given this much, a typical bare basement floor is everything most of us hate underfoot: it’s cold, hard and ugly. That’s why so many homeowners choose carpeting for finished basements. Just roll it out and you’re done. But used alone, or even with an under pad, carpet is a risky proposition below grade. And the source of this risk is invisible moisture. Even apparently-dry basements can develop moisture problems during humid weather, when condensation occurs on cool floor surfaces. That’s why you need to consider some floor insulation strategy upfront. Carpet alone isn’t good enough because warm, moist air percolates through the fibers and condenses at the bottom of the pile. And too often this process is enough to make it smell like you’re living with a wet dog. Basements don’t have a musty reputation for nothing. There are two approaches I favour for basement floor prep. The one that offers maximum insulating value starts with a layer of 1 1/2 or 2-inch thick extruded polystyrene foam placed against the concrete, with a layer of 5/8-inch plywood on top. The whole thing is secured with Tapcon screws torqued directly into pre-drilled holes in the concrete floor. You get a warm, dry, all-wood subfloor that’s ready to take almost any kind of finished flooring safely, including carpet.

Your home may feature every basement waterproofing strategy known to mankind, but there’s still no guarantee that, say, a week of torrential downpours won’t overwhelm your bulwarks. And if this possibility concerns you, consider a second type of basement floor strategy. It uses a new type of product made of interlocking tiles of water-resistant wafer board, bonded to a dimpled plastic layer. This plastic separates the wood from the concrete floor, while preserving small drainage channels between the two. You certainly don’t ever want water to trickle into the space under the floor, but if it does there’s no disaster. There’s still a clear path to the floor drain. Sublfor is one brand that I’ve tested and like. Even when submerged underwater for three days, the wafer board substrate remained solid, with minimal swelling.

Do you like the look of a wood floor in the basement? That’s okay, too, just consider laminate flooring instead of solid wood. Laminates are much more moisture-resistant than the real thing, especially if you choose edge-glued types. In fact, major laminate manufacturers all warrant their product for basement installation, even directly on concrete covered with a thin underlay. Laminates will certainly do fine on top of either of the insulated floor strategies here. There’s one more thing you need to understand about basement moisture control. Humid, summertime air is a potent source of moisture, triggering the formation of mold and mildew even if all obvious moisture channels have been plugged. That’s why it’s important to keep basement windows shut during hot weather. A dehumidifier is the best way to keep basement moisture levels down between 65% to 75% R. H. at a time of the year when open windows might let relative humidity skyrocket to nearly 100% in any cool basement.

Warm and Bright Basement

In the same way that porous items like wood and carpet aren’t the greatest things to put against concrete basement floors, basement walls deserve unique treatment, too. A unique rigid foam product called Styrofoam Wallmate includes channels for lumber that serves two purposes. First, the wood acts as a big washer, allowing the foam to be held to the wall with screws or concrete nails. And since the wood sits proud of the inside face of the foam, it serves as an effective nailing surface for interior wallboard. There’s nothing physically special about the extruded polystyrene foam used in this product, besides the channels for wood. You could use conventional, channel-less sheets, though they’re less convenient. This wall-foam strategy doesn’t conveniently deliver as much insulation as a stud frame wall insulated with fiberglass, but it’s much better suited to basement situations. Foam is a moisture-tolerant insulation product because it’s both rot-proof and impervious to water — two big advantages when it comes to any basement situation. One more thing about basement heating comfort. If you’ve got a forced air furnace system, go to the trouble of extending cold air return ducts to the floor of the finished basement area. This creates the necessary ceiling-to-floor air flow required for even heating. Depending on your heating system, it may also be necessary to install booster fans inside existing furnace ducts to assist air flow. Many older forced air systems were never designed to heat the basements they pass through. If such a deficiency is marginal, then a duct booster can help.

Warm and dry is good, but who wants to live in a dark hole, illuminated only by artificial lights? That’s why it makes sense to consider maximizing natural light sources into the basement. Extending basement windows downwards is an option in a few cases, as is increasing the number of basement windows. But a more useful strategy is the installation of tubular skylights. They’re like big-diameter fibre-optic cables that funnel light downwards, around corners and even between floors. Australian-based Solatube is the originator of this technology, but others are following now. A web search of the phrase “tubular skylights” yields a handful of company names. I installed a unit in my own home and it works wonderfully. Say you’ve got a storage area above the spot in your basement where you’d like to have light. Tubular skylights can funnel down tons of great light from roof surfaces as far away as 14 feet away. You can even fit them with internal light fixtures wired to come on when neighboring lights are energized. After you’ve got the infrastructure of insulation, heating, and natural light sources in place with, finishing a basement is a lot like any other home renovation, even if it is taking place in what began centuries ago as an underground potato pit.

Sidebar: Basement Soundproofing

Finished basements are successful only to the extent that they allow more activities to occur in your home. But noise-based interference can short-circuit some of the space gains if you’re not careful during the planning and building stages. What’s the use of having a posh and comfortable finished basement if it means your own teenagers and their friends drown out your prime-time TV shows using the stereo equipment you paid for? That’s why an understanding of soundproofing needs to be part of any successful basement upgrade. Don’t assume that sufficient soundproofing will happen automatically, because it won’t. In a nutshell, consider three technical features: resilient metal channel to lower sound transmission through dry walled ceilings to upstairs living areas; staggered-stud framing for sound-critical walls; and the use of acoustic caulking to seal the drywall-to-framing joints in walls that must inhibit sound. One of the best online sources of soundproofing info I’ve found is www.soundproofing.org. It’s a commercial site, but still worth visiting.

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Posted on November 21st, 2010

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