Block vs poured foundation wall?

I'm having a 400 sq ft garage addition built this spring and the builder is asking if I'd be okay with a cinder block foundation wall as opposed to a poured foundation. I prefer a poured foundation so it matches the existing foundation (stamped brick look), but I believe only about a foot of foundation would be exposed above grade for the majority of the structure, whereas the more exposed portions would be concealed by a deck. He said I wouldn't see the mortar joints and it would have a smooth finish. This doesn't sound too bad, but I have concerns about the integrity of this smooth finish as it ages. I envision chunks of concrete flaking off the wall over time as things settle. I live in northern VA, so there is a lot of freeze/thaw every year (as low as single digits in the winter and as high as 100 in the summer). The foundation will be just under 100 linear ft with an average height of 5 ft. Approximately 2/3 of the wall be 3' to the footer with 1' exposed above grade and the other 1/3 (back of addition) will be 6' to the footer with 3' above grade. He told me the block would be a 40% cost savings, but he didn't say exactly what the savings would be. I was under the impression that an entire poured foundation was going to be maybe $2k to $3k max, so if the cost savings is $1,200, then I'd likely go with poured as initially planned. I'm thinking his reason for using block may have to do with minimum order quantities and/or minimum yardage and the cost of getting relatively small loads of concrete?

 

structurally there is no difference. all my houses have been poured basements with block for the garage. I don't recall any being more than 1-3 rows deep.

Suspect the savings is coming from the set up time for the forms vs a couple of guys just laying the block.

you mention 5' of wall, is that due to elevation or getting down to good soil?

 

I gave an average wall height of 5' for concrete cost analysis. All footings will be 2' below grade. The yard slopes downward towards the back of the addition, which is where the foundation will be about 3' above grade. I estimate about 10 yards of concrete for the wall only.

 

I think it's a cost issue. Setting up the forms for a small pour like that is more expensive than setting block. Also filling a wall would require the labor for guys with wheelbarrows or hiring a pump which isn't economical for a small job. I'm sure it could be done but you'd have to get the price to see if it's worth it to you. I would be more concerned about getting poured walls if you had a basement but for a crawl space it's more a cosmetic issue.

 

Thanks for the feedback. That makes sense. I guess I'm okay with a block wall considering there isn't a basement and only about a foot would be exposed. I'm waiting to hear back from a buddy of mine that owns a concrete business to see what he says.

 

... also you could float stucco over the exposed block to make it closer resemble the poured foundation.

 

Yes, I would do stucco if I go with the block. However, the existing foundation is brick-look, or whatever you call it (the forms had a brick pattern on them).

 

You can probably replicate that look with stucco.

 

By the time you install the siding and any landscape it will simply disappear!

 

With equal back-fill each side, CMU or concrete block (probably not cinder block) will be adequate. However a poured wall is, by far, structurally superior.

 

I am thinking of using block for a foundation wall for a 2400 sq ft a-frame. Was wondering if I may get away with 1-2 courses of block. Any thoughts? Ideas? Trying to keep cost down.

 

As stated in your original thread,http://www.doityourself.com/forum/br...mu-blocks.html, your block will need to be above grade when finished, so we don't know how high that will be from your footing.

 

Save a dollar now to spend hundreds of dollars later? Sorry, but it makes no sense to me.

For long-term durability and best performance, go with reinforced concrete. End of discussion.

P.S. It sounds like your contractor doesn't have a thorough understanding of the attributes of CMU walls vs. reinforced concrete walls. Maybe time to look for a new contractor?

 

My last house was 60 years old and had a block foundation with stucco over the block (cottage cheese finish). I had no problems and no questions came up when I went to sell it. I live in the Midwest where we have constantly shifting temps in the winter (60 degrees one day and 10 the next) and very hot summers.

 

How much do you think I'll be saving with going with a block foundation as opposed to a poured one? I have no idea. Is it really that much more to have a couple guys set up some forms compared to the labor involved with setting block?

Another unknown is th e builder is telling me having a 45 degree wall in my mudroom (15 feet long) is going to be significantly more expensive, but he hasn't specifically told me why. I realize some angles will need to be cut, but I don't see why that is a big deal. Maybe it's tying the angled wall into the existing foundation? Even then, just drill at an angle. Doesn't seem complicated.

 

My only comment is that cinder block walls seem to have a higher probability of being pushed in due to ground conditions, freezing, etc. Lots of web sites discuss the issue, and mention that a poured concrete wall statistically does better. But of course both depends on the engineered design and actual built product.

Up here in my part of Canada where go from over +30c to sometimes below -20c (so a 50+ C degree difference) a block wall is rarely ever used. I've never seen one personally. Poured concrete is the only thing used.

So you might save some money now, but be back on this forum in a few years asking how to stop your walls from bowing or leaning inward more. And of course that costs the bucks!