Why aren’t more foundations structural brick?
I may be showing my youth here, but I’ve been pondering a few odd ball questions, and looking back at old building techniques, and I started to wonder to myself “why not build a foundation from brick?”. My initial thought (like yours might be), was “Jeez, what is this, 1930?” Until I actually started to compare it to CMU foundations, I thought it was heresy. However,
1) The strength of a CMU wall is limited to the same mortar strength as a brick wall
2) A brick is easily 2-3 times stronger than a CMU
3) A double wythe brick wall is already solid, compared to an ungrouted CMU wall
4) A single brick weights about 1/8 of a CMU, reducing fatigue
I can see how a reinforced, grouted CMU wall would beat a brick wall hands down, in terms of labor, strength, and ease of construction. The only way I can see an ungrouted CMU wall being advantageous over a brick wall is in terms of labor costs, and perhaps material costs, thought I haven’t priced it out.
My question(s) of the evening is this – If costs were not a concern, would a brick foundation be a viable alternative to an ungrouted CMU foundation for say, a crawl space? What disadvantages exists that would make a brick foundation worse? Could a reinforced masonry foundation surpass a grouted and reinforced CMU foundation?
Thanks for entertaining a long winded rambling thought!
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Replies
Big issue is cost and labour, brick foundations are usually triple wythe (lot of brick and a lot of brick laying). CMU foundations are popular because they are cheap to put up.
Foundation bricks are not normal bricks, I can tell you from having drilled through them, they are hard as rock. These bricks a specifically for bellow grade, I never had to price these out but I'm sure they are not cheap.
Brick foundations also leak like a sieve, so you do have do proper waterproofing. Can't get away with the typical roll or spray on dam proofing.
Usually when construction industry moves away from a technology, it is because of cost. Brick/stone foundations were replaced by concrete because they are cheaper to build.
Thanks for the input Akos. - Can I press you on that second point? Does a brick foundation leak more or less than a CMU foundation? From what I've seen from CMU walls, I don't see how brick could leak more, CMU might as well be transparent to water. There's a big disclaimer here, I've built with CMU, but never with brick in the same way.
Block walls (I mean "building blocks" here, so brick or CMU) tend to fail at the mortar joints. That would mean more mortar joints = more places for failures. A brick wall has a lot more mortar joints, so many more places to potentially fail.
In terms of water leaks, I've never really thought much about that. Typical CMUs are rather porous, but mortar joints can be leaky spots too, and brick has more of those. Is it a wash in the end? About the same either way? I don't know. I'm going to defer to Akos here, who claims brick foundations "leak like a sieve". Waterproofing is a must either way.
Bill
To take this a step further, why not build a foundation from big chunks of sandstone (in areas of the country where it's a commonly available resource). I wonder what the carbon impact of quarrying and transporting sandstone is vs. concrete production? I once saw an old house, that was converted from an older barn, where the foundation / walk-out basement level was huge sandstone blocks -- sure looked solid!
Jonny,
Unfortunately sandstone shrinks and swells as it takes in moisture. Dry-laid it would work, but then you would still he the problem of the joints.
A quote from an interview with Martin Holladay:
"Martin: No. My house is a hippie house put together with sawmill lumber and logs I cut down on my land and fieldstone that I gathered in a wheelbarrow.
克丽丝:你会做一遍吗?
Martin: No, I wouldn’t. "
No matter how careful the mason, there will be spots with no/weak mortar eventually. Water will happily find these small holes. Since these gaps can be quite large a typical roll on damp proofing will not seal them like it will with the pours surface of CMU.
Because of the distance between brick layers, water can leak in one area, flow along the gap and leak out through a another weak spot elsewhere. This makes finding the source of the leaks pretty annoying.
Leak like a sieve comes from personal experience of having a small stream of water running through the basement with any amount of rainfall. I have seen cracked CMU weep a bit of water but nothing like this. In my case, peel and stick+grading fixed it, so a bit of good detailing up front can make it work.
P.S. If you are looking for extra strength, I saw interesting detail in an older CMU build. The block wall had brick columns built into it to support point loads. Grouting the CMU is still quicker though.
That's an interesting detail, I wonder if it was for aesthetics more than utility?
I agree on the mortar / brick ratio, compared to the mortar / cmu ratio. There's a lot of potential there for leaks.
It was a garage with two large I beams sitting on the brick columns. Definitely for utility.
Cost and more leak prone. In any case in my area the material of choice is poured concrete.
same here, poured concrete is the best, block is done to save $$