Fawning Over Foundations

When it comes to foundation construction in Canada, there are essentially 3 methods to consider: Block, Poured or ICF. Each is made with concrete, they all must be constructed on top of a concrete footing, and proper waterproofing, insulation and drainage is a must. This all sounds great, but what’s the difference?

Concrete Block
Let’s start with the quick and dirty solution. Block foundations are constructed by arranging a series of concrete blocks on top one another, each being held together with mortar. They are constructed in a straightforward manner, don’t require forming, require little maintenance, and are pretty much available everywhere. As a result, a talented mason can build the foundation relatively cheaply and quickly.

However, it’s not uncommon for moisture to weep through the walls and cause all sorts of problems. If improperly waterproofed, I suppose each approach is vulnerable to moisture in one way or another, but block construction is especially susceptible because of the amount of mortar used and the porous nature of the blocks themselves.

Poured Concrete
Poured walls are also quite common, however their construction is a little more involved when compared to a block wall. Before the concrete can be poured, temporary forms must first be erected. These forms create a hollow structure in which the concrete is poured, and they remain in place for about a day until the concrete has started to cure. As a result, labour costs are greater as you’ll need a crew to erect and dismantle the forming, plus you’ll need to coordinate the concrete delivery and pour.

Poured walls do result in a stronger structure (so long as the concrete mix is correct), so you can typically go deeper than you could with a block wall. Definitely a plus if you’re looking for higher basement ceilings.

Insulated Concrete Forms
We opted for ICFs, which are somewhat of a hybrid in that they require both blocks and poured concrete. According to the trusty Wiki, ICFs are described as a “stay-in-place formwork for energy-efficient, cast-in-place reinforced-concrete walls”.

There are a variety of companies that offer a variety of ICF solutions, but they all basically work the same way — Foundation walls are erected out of reinforced polystyrene foam blocks, and those blocks are then filled with concrete. Rebar is often inserted or integrated into the block for added strength, and temporary shoring is required for additional support during the pour.

ICFs are considered the “greener” solution because of the vast benefits they afford; even temperature, fewer drafts, fewer hot and cold spots, consistent floor-to-ceiling temperature, noise reduction, strength, and durability. But the real beauty of ICFs is the inherent insulation value that comes with the foam. There appears to be lot of varying opinions on the matter, but if the thermal mass and air-sealing effects of the concrete are considered, it’s argued that the effective R-value of ICFs is somewhere around 40+.

ICF foundations will ultimately cost more than other two solutions, but you’ll make up the difference in materials and labour costs as you don’t have to frame or insulate the basement (drywall affixes directly to furring strips built into the blocks), plus the energy savings that result from the higher R-values.

Once again, the greener solution costs more up front… however, it also appears to be a smarter investment with all things considered.

Photos via finehomebuilding.com & Flickr

Post Tags: block, concrete, foundation, ICFs, walls

Posted by Jeremy Bell in: Construction + Eco / Green + Materials