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House on slab foundation built in 1965. Along one side only the cement blocks visible at ground level are deteriorated. I am thinking poor quality product. The ground is flat and water probably sits along blocks, so maybe that has something to do with it. Being a slab I really can’t see anything and am not sure what to make of this.

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I'm interested in why someone would put concrete blocks around the perimeter of a slab foundation. I've never seen such a thing. What possible advantage is there to it?

Must be a regional thing. I've never seen a slab foundation that WASN'T surrounded by concrete blocks. Around here, the block walls are laid first, and then used as "forms" in which to hold the concrete till it sets.

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Dig out footer trenches, pour a footer, build up a stem wall to ground level, fill the area inside the stem wall with gravel, pour the slab.

They do paint the block exposed above ground with concrete (parging) but they do such a crappy job that it's falling off and showing the mortar joints within a year or two.

That's about how it's done around here.

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Posted by Erby - Sep 28 2011 : 05:00:26 AM

Dig out footer trenches, pour a footer, build up a stem wall to ground level, fill the area inside the stem wall with gravel, pour the slab.

They do paint the block exposed above ground with concrete (parging) but they do such a crappy job that it's falling off and showing the mortar joints within a year or two.

That's about how it's done around here.

.........same here, with footers below frost line.

......Greg

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That is how they build slabs in my area as well. Form a pad, footers, place CMU, (my home has 3 blocks), fill about 2/3 with crushed rock, trench for plumbing, add in under slab plumbing, add steel/rebar then pour in the concrete to the top of the CMU and fill voids in blocks(set foundation bolts). Allows a slab foundation to built on uneven grade similar to a conventional foundation but the cost is less.

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That is how they build slabs in my area as well. Form a pad, footers, place CMU, (my home has 3 blocks), fill about 2/3 with crushed rock, trench for plumbing, add in under slab plumbing, add steel/rebar then pour in the concrete to the top of the CMU and fill voids in blocks(set foundation bolts). Allows a slab foundation to built on uneven grade similar to a conventional foundation but the cost is less.

We do it the same way, except we cast the stemwalls from concrete. Building them from CMUs would be viewed as kind of cheezy. Of course, I still can't get over the fact that you guys use CMUs to make basement walls either.

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Kibbel will most likely correct me, but parging was used in old buildings as a lime rich sacrificial layer on brick foundations to encourage the corrosive salts associated with "rising damp" to leach out to the parging instead of attacking and demolishing the primary structure. It was also used (sort of) as a barrier to "outside" water leaching into the building; all that beautiful lime would inhibit capillary migration into the foundation.

So, you coat a cheesey block wall with paint or Portland, it does nothing but accelerate the deterioration. This block probably soaked up enough water from both directions to demolish it.

Or, something akin to that.

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That is how they build slabs in my area as well. Form a pad, footers, place CMU, (my home has 3 blocks), fill about 2/3 with crushed rock, trench for plumbing, add in under slab plumbing, add steel/rebar then pour in the concrete to the top of the CMU and fill voids in blocks(set foundation bolts). Allows a slab foundation to built on uneven grade similar to a conventional foundation but the cost is less.

We do it the same way, except we cast the stemwalls from concrete. Building them from CMUs would be viewed as kind of cheezy. Of course, I still can't get over the fact that you guys use CMUs to make basement walls either.

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With newer homes I never see CMU basement walls. Most if not all are now cast concrete. Every now and then I will find a cast stemwall on a crawlspace, but it is not common.

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