Cinder Block foundations

[jlybolt]

OK. New construction pier and beam home with cinder blocks for piers at perimeter wall and interior. Pads at grade level and no anchorage to structure visible. I would think the pads would need to be a min. of 24 inches below grade to help prevent differential movement.
Although I am not a code inspector but the IRC Does not appear to address construction of a foundation with 8" x 8" x 16" cinderblock piers. My question is why is this type of construction not addressed in the IRC since this is a typical type of construction seen in older homes and what are some guidelines to follow while inspecting these type of foundations. Any help would be appreciated.

[Richard A. Hetzel]

Do you literally mean "cinder block" or do you mean concrete block? There is a big difference. And how does a pier have three dimensions like that? Usually piers are described by their cross-section: 8x8, or 8x16, or 16x16. I guess you are decribing the block size. What do you mean by "pads"? Do you mean concrete footings? If so, and if they are poured directly on grade, and not dug into the soil, are you worried about lateral movement? What force would be strong enough to overcome the friction between bottom of footing and soil and make the footings move laterally?

[jlybolt]

ok concrete block. Here is a detail that I found from local building department. I have attached it in PDF format. Notice the concrete pad or I guess footing. Its a mininum of 24 inches below grade with reinforcement.. Im a little confused, where can I find the information that says you can pour a footing on grade. Thats what I am trying to find. Even the IRC has a mininum footer depth depending on one story or two story home.

[Larry D. Kage]

Originally Posted by jlybolt

ok concrete block. Here is a detail that I found from local building department. I have attached it in PDF format. Notice the concrete pad or I guess footing. Its a mininum of 24 inches below grade with reinforcement.. Im a little confused, where can I find the information that says you can pour a footing on grade. Thats what I am trying to find. Even the IRC has a mininum footer depth depending on one story or two story home.

If the site matches your PDF, it is not poured on grade. Your PDF shows a minimum 24" below grade.

Around here, that depth (24" below grade) is the minimum in well drained soils.

[rwand1]

24" to undisturbed soil.

The concrete block appears to be grouted with concrete. Looks fine to me.

[Michael R. Boyett]

Here's a paragraph from a local (Central Texas) foundation repair company website:

Many homes prior to the mid 1960s were built on cedar post piers, .... Another common type of support method used in more recent pier and beam construction is the block and pad pier. Block and pad piers are designed and utilized to perform the same function as cedar post piers. At each pier location a shallow pad of concrete is poured directly on top of the ground below each beam. Concrete blocks are then placed upon the pad and stacked to provide support under the home's beams. In many instances, the footing poured directly on top of the ground is adversely affected by the expansion and contraction of the soil at the surface level resulting in an inability to provide the proper amount of support for the structure.

[jlybolt]

I understand the pdf looks good. The pdf is something I got from the building department.

The problem is that the new home I inspected yesterday, the pad was at grade level and did not go down 24 inches or until undisturbed soil. I was able to basically touch the bottom of the pad or footers if you like with my hand. The whole house was built this way.

I am trying to find something that says its ok to build this type of pier without going to undisturbed soil. The IRC does not appear to address this type of pier construction but does have min. depth requirements for footers.

Would you recommend further review by a qualified foundation company if the pad or footer was not a min. of 24 inches below grade? Its a hard call for me since I have seen many older homes built this way, doesnt mean its right.

[jlybolt]

Hey Micheal. How is it going? You got the idea. My opinion is if the footer or pad is at grade level your going to have movement. In a new house I cant see this being a good thing. New home owners dont usually like cracks everywhere. This soil at this site was definitely expansive. There has to be some guidelines on how to do this properly.

If the pier was built like in my pdf I would not have a problem with it.

[Richard A. Hetzel]

If you're going to have movement with the footing at grade, you're going to have it if it's founded 24 inches below grade, too. Usually interior column or pier footings are not required to extend the same depth below grade as the exterior footings, and if there is no danger of frost, then there is no reason why footings on grade won't be satisfactory.

[jlybolt]

Richard I tend to disagree. Expansive soils are very common in this area and the home I looked at (4 months old) had noticeable differential movement already. In my opinion lots of this settlement could have been avoided by proper pad depth or if you like footers.

[Richard A. Hetzel]

Oh. Expansive soils are only on the surface?

[jlybolt]

See post #3

[Richard A. Hetzel]

Shall I list all the things that are wrong with that silly diagram? Starting with the title?

[rwand1]

Yes please do, it would be interesting to know what is wrong.

Thanks,

[jlybolt]

I didnt draw the silly diagram. The building department did. All am looking for is documentation that says you can have a footer or concrete pad at grade level and build a home (not a mobile home) on top of it?