In my newly adopted town, in eastern Ontario, I’ve noticed that all new homes are being built with ye olde masonry blocks for the foundation.
Why is that?
The ground here is very extremely sandy. Would that play into the equation?
I’ve never seen a house built with blocks in like forever.
Thoughts?
Concrete is relatively more expensive than labor? Strong union? Tradition? Appearance?
Here in northern Ohio, CMU construction is most common. Formed concrete is found on far fewer homes. Nice concrete work, molded to appear like bricks, even less common.
Any contractor with a big backhoe and a bunch of guys can build a CMU house. It takes many thousands of dollars of forms to form a basement, pump trucks must be rented, etc.
In the last few decades there has been an increasing concern about minimizing heat loss in houses–and a significant amount of heat loss goes through the foundation.
The new way to do this is insulated concrete forms (ICF).
http://www.cement.org/think-harder-concrete-/homes/building-systems/insulated-concrete-forms
I’m surprised you aren’t seeing any of this.
That’s got absolutely nothing to do with what I asked about.
In order to use poured concrete, you have to be within a certain amount of drive time from the concrete plant (you don’t want your concrete getting hard and solid while it’s still in the truck). Maybe there isn’t a concrete plant within a reasonable drive time to where the new construction is?
Another possibility might be scheduling. A block foundation is done when it’s done. A poured concrete wall has to cure.
A block wall is better in compression, where a poured wall is better when subjected to lateral forces. Some architects and builders have a preference for one or the other.
In sandy ground it’s best to use concrete reinforced with steel, but poured foundations and block foundations can both be reinforced with steel so that’s not an issue either way.
The labor rate can factor into it as well. When the economy is going well and the labor rates are up, poured is cheaper. When the labor rates go down, the labor cost of a block wall is a lot more competitive.
Not quite. Drive time is only a matter of convenience. I’ve seen concrete poured on mountaintops, about 4 hours drive from the nearest city.
You just deliver the cement powder (in sacks) to the site a day earlier. When the the concrete mix truck arrives, you add the powder to the mix.
Sandy and loam type soils don’t expand when wet like clay so block foundations are likely cheaper and with little lateral pressure - good enough.
They’re never cheaper. If labor costs are low enough they don’t cost much more. And if it’s like it is around here there are only a few contractors for the poured foundations and they ask top dollar now so the costs are even closer. But the labor will always make blocks cost more.
We saw some growth in pre-cast foundations around here for a while. Usually footings were poured but they could bring in huge sections of that also. The walls were put up and bonded together in a day and the construction could start immediately with no cure time. So maybe that’s the advantage, ‘just in time’ construction. Since it’s in Canada and there’s only about 6 weeks a year above freezing the time factor may be the reason, a poured foundation needs weeks to cure.
I can think of two more reasons. CMUs can make more sense for a small contractor building one house at a time. A big developer is more likely to prefer poured concrete. The other reason is a basement. If you have to pour a basement slab, there is an incentive to pour the foundations as well.
As for timing, poured concrete sets very quickly. You can walk on it the next day and start framing walls.
Well, there are plenty of concrete suppliers here, so delivery time isn’t an issue. Labour costs would be fairly standard; the employment rate here is slightly above provincial averages.
There must be a physical reason why block construction in a sandy environment would be beneficial. I can’t seem to discover why, and it’s bugging me!
Ask the builder.
I am curious to hear the reasons too, but as engineer_comp_geek suggests it may have less to do with sandy soil and more to do with labour / supply issues.
AdamF - I have never seen slab poured at the same time as foundation walls when building homes here in Calgary. It is actually a 3 pour process - first the footings, the foundation walls after that has set. Much later after framing, HVAC, plumbing and electrical is the basement slab is finally poured. You can add a fourth and maybe fifth pour for driveway, walkways/patio and garage slab.
PastTense, ICF is not exactly new, I built with it ten years ago. Half of the foam insulation is on the inside where it does not make use of the concrete mass as a thermal sink, and must be drywalled for fire code. It is a royal pain in the ass for electricians, so it is tempting to frame a frost wall just like you would for concrete. I built three during the boom when cribbers were expensive and hard to schedule. It allowed us to save some time and use our own labour. The next home I built after that was cribbed and we insulated the exterior in a few hours with foam. For most purposes, including energy efficiency, I think exterior insulated concrete is superior to ICF. I do see them used for party walls in duplexes, and have considered this for the next time I build one. It makes for a very sound proof wall, but I think a CMU wall would be just as good. Labour, scheduling issues, final wall width and cost of a CMU contractor will all play into the final decision.
The basement slab is poured well after the foundation. Usually after the roof and siding are done. Since it’s going to be done at a seperate time, no benifit to tying the slab to the foundation. They can pour a slab just fine in a cinder block foundation.
In my area, Massachusetts, I haven’t seen a new construction with a block foundation in my lifetime. There are plenty of older homes that where built with them. Also a number of really old homes where full basements where added using block walls. The overwhelming majority of new construction use poured concrete. A very small amount use precast concrete foundations.
As I have to core through foundation walls as part of my job I prefer poured foundations because I can core through them cleanly. Block walls are easy the get through but not so easy to do cleanly. The precast with foam insulation are a disaster, the concrete is thin and crumbles in all directions.
I did not mean to imply that you would pour footings and slab in one go, though you could. I was saying that it would be uncommon for a builder to pour footings and then build the basement wall out of CMUs.
That’s not uncommon at all where I live, and in fact is the most common method. Poured basement walls are not rare by any means, but neither are CMU walls. I’d estimate new construction is about 50/50 around here. The standard process is to a) pour the footers, which set up in a day or so; b) lay the concrete block foundation OR set up the forms and pour the basement walls, and move on with framing and then mechanical work; and c) pour the basement floor. I’ve never seen footers that weren’t poured, but I’ve seen lots and lots of block basement walls.
Just a guess, but an educated observation (validating a prior post): small builders are far more apt to lay blocks, whereas larger “production” builders are more likely to pour basement walls.