360 Winnett » foundation

Poured Foundation

jeremybell — Mon, 22 Sep 2008 23:46:14 +0000

It’s been a few weeks, and we’ve made quite a lot of progress on the house. We had evaluated a number of manufacturers, but ultimately decided upon Nudura for our ICF foundation. Paul Stevens and his crew from Stevens Construction handled the formation and pour of the foundation, and by all accounts they did a smashing job.

The Nudura product comes shipped in a collapsed state, which I believe reduces shipping costs and makes it easier to handle by the workers. The ‘blocks’ look to be about 7’-8’ long, and they basically just snap together. For the odd sizes, the blocks are simply cut with a handsaw. A crew of 3 guys assembled the wall, and the process looked to be pretty straightforward:

First, the footings are formed and poured. The footings are basically a short concrete wall that the ICF blocks will sit on, and their main purpose is to displace the weight of the structure above.
Once the footings have cured, the forms are removed and 2 metal strips are attached. The strips were used to keep the bottom row of the ICF blocks straight and true.
The ICF blocks were then assembled and wood planks are added (in certain areas) for additional support. Permanent wood forms are also built to create the window wells.
The blocks themselves have a “mesh web” built into them, but additional horizontally and vertically rebar is also placed inside.
Large metal braces are temporarily installed to support the wall during the pour. These braces acted as a walkway for the crew during the pour, plus they were also used to fine tune the straightness of the walls once the concrete is poured.

Additional wood bracing was also added throughout to ensure the structure is maintained during the pour.
This isn’t exactly on par with the demolition video, but here’s a little video that illustrates how the foundation walls came together.

Once everything was formed, supported and ready for concrete, I made a point of calling our architect and setting up an inspection before the pour. Nothing too major was out of place, but there were a few things that needed to be adjusted to ensure we maintained the aesthetic we were trying to achieve (one wall was jutting out about 6 inches further than it should have and would have resulted in an unsightly ‘hump’ in front of the stairs). We also decided to abandon the window in the study under the garage. I had raised concerns about this earlier on in the design process, but we made the decision on-side because it quickly became clear that the window well would have been too large for the space along the house. Once these oversights were corrected, it was time for concrete.

A relatively liquid concrete was poured into the hollows of the ICF walls, which allowed it to easily slide through the webbing and rebar. The crew would walk around the walls and fill it up a few feet, and then continue around to fill it another few feet. Every so often they’d stop and use a large vibrator to ensure all air bubbles were worked out, and the concrete made its way into every crevasse. I definitely have to give some credit to Paul and his team – lugging around the pumping house didn’t look like much fun.

The walls stayed untouched for a few days to allow the concrete to cure, after which the the weeping tile, crushed gravel, sand, and backfill were added. Sand was used because it allows for better drainage, and the weeping tile is basically a plastic, sock-covered tube that wraps around the perimeter of the house. It’s sole purpose is to capture any water that seeps into the ground, and move it away from your foundation. In our case, we have a “soak away” pit in the backyard which will capture most of the rainwater runoff and allow it to dissipate naturally into the ground.

I’m definitely glad we’ve moved past this phase, as there were a few hiccups we encountered along the way which increased the foundation budget by about $2000. In particular, we had a little turbulence between the trades and the structural engineer, but I’ll explain this in another post soon.

ICF to the roof?

jeremybell — Wed, 16 Jul 2008 03:24:07 +0000

I’ve already discussed the benefits of using ICFs for our foundation, but we’re now considering using them to construct the entire building envelope. We had originally expected it to be cost probative, but after getting a few quotes it appears to be comparable to traditional stick framing with spray foam insulation, which makes it far more palatable than we anticipated.

As with the foundation, the main benefits are the same: Fire Resistance, Sound Resistance, Durability, Energy Efficiency, etc.

I’m not anticipating we’ll see the benefits of their fire resistance, but it’s comforting to know it won’t exactly burn down in a matter of minutes. I’m also not expecting the home will see many wind storms or earthquakes, but I know it’ll hold its own in the face of mother nature.

Sound dampening is another great byproduct, which really shouldn’t come as a surprise once you think about it. The foam and concrete acts as a sound barrier, which dampens sound vibrations and renders the interior eerily quiet. I can’t say this is something I’d necessarily seek out, but it’s also something I won’t complain about it.

I suppose the most valuable benefit of using ICFs are the inherent energy efficiencies that they provide. The foam alone accounts for an R-22, but if you take into account the thermal mass of the concrete, you end up somewhere around R-40+ (or so they say). Similarly, the continuous application of foam and concrete ensures there will be minimal air leakage, which furthers the structure’s energy efficiency.

From a construction standpoint, we’ll also see a number of additional benefits such labour savings and speed of deployment. But of course, we’ll also see a few drawbacks.

Our design calls for 2 cantilevered overhangs, however the concrete adds a considerable amount of additional weight which hasn’t been taken into account. As a result, we’ll have to reevaluate our structural needs and will probably substitute steel for of the engineered wood beams we’ve accounted for.

Another issue we’re facing is a slight reduction in usable space. If you look at the 1st floor drawings, you’ll see we’re already pretty tight between the kitchen, stairs and garage. It may not seem like much, but the ICFs will consume an additional 4 inches on both sides of the house and we’re a little concerned about loosing those 8 valuable inches. Altius has some ideas, but I think we’ll ultimately need to be a little creative to make it work.

We haven’t made any decisions yet, but we have a meeting this week with our contractor, architect and ICF installer to discuss the realities of this approach.

Fawning Over Foundations

jeremybell — Thu, 26 Jun 2008 03:00:32 +0000

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

Under The Garage

jeremybell — Mon, 23 Jun 2008 13:07:10 +0000

I don’t believe this is particularly common, but we’re planning on building two extra rooms in our basement by excavating the space under our garage. In a typical garage, the floor is simply a concrete slab that sits on top of soil, however we’re going to approach things a bit differently.

Because our foundation will be built with ICFs, we’re planning on utilizing a “deck” system that will integrate a structural concrete slab directly into the foundation itself. This means we’ll be able to pour concrete for the foundation walls and the garage floor at the same time. When everything cures we’ll have a structurally sound garage floor capable of supporting the weight of a car, plus a completely insulated 10×20 space below it.

The decking system is pretty straightforward to install—Once the ICF blocks have been assembled, the foam deck panels are placed across the span that makes up the garage floor. These panels are then supported from below with temporary shoring and reinforced with rebar.

Obviously this approach is going to cost a little more, what with the additional concrete and rebar and foam panels and labour, but we’ll be gaining an additional 200 sqft of space that would have otherwise been inaccessible. If you take a look at our floor plans, you’ll see that we’ll have a very generous “study” and additional storage down there… which I’ll say is a decent use of that space, no?

For those itchin’ for the nitty gritty of how a system like this is installed, I also dug up a PDF aptly named Pouring A Structural Slab that explains it all.

How Green is Green?

jeremybell — Tue, 03 Jun 2008 03:07:57 +0000

What exactly spurs someone to take on a project like this? After 5 years in a small pre-war bungalow, my wife and I decided we wanted more room to start a family. So for us, this project was born out of a need for more space.

However, at some point along the way, our priorities changed. We still need the extra space, but I came to realize we could build a better home instead of a bigger home.

I’m sure “better” means something different to everyone, and for us it originally meant a modern esthetic with nice fixtures. And while we still want this, I’ve also come to appreciate how sustainability must work into the equation. So I’m left wondering… how green is green?

I’m not sure I have a definitive answer for this, but we are trying to do as much as possible given our budget. I’ve heard many claims that “green” doesn’t necessarily equate “expensive”, and while this is true in some cases, it’s hard to argue when you look at the budget. The fact is, we could have built a much larger home if we wanted, but instead we reduced the footprint so we could build it greener. I’m not suggesting it’ll be the poster-child for LEED construction, but it’ll definitely be better than it would have been.

I’m planning on discussing these more in future posts, but here a few things we’ve considered with the design of the house:

Window shading
Passive lighting
Passive heating & cooling
Rainwater collection
ICF / SIP construction

Spray foam insulation
Beyond the products & practices we’re considering, I’m often asked about the existing house. Why did we decided to bulldoze it? Why not build on the existing foundation? If we are going to demolish it, what will happen to the waste?

These are all excellent questions, and I must admit I hadn’t actually considered all of them. We had originally intended to build on our existing foundation, however proximity to our neighbors made this problematic. And I would love to recycle/reuse everything… I just don’t think that’ll be entirely possible.

Crushing and reusing the foundation is an intriguing possibility given our flat roof (we’re investigating covering it with crushed gravel). As for the rest of the house, we’re going to be selling/giving away as much of it as possible (the kitchen cabinets, radiators, boiler, etc). However, I realize that won’t make much of an impact and I assume most of it will end up in a landfill.

Not exactly the most eco-friendly solution, but that’s where we stand today. I hadn’t considered recycling the rest, but it’s something I’m definitely going to look into it now.

So these may not all be the greenest of steps, but hopefully they’re steps in the right direction.

Photo via Flickr user CasualTea