Mixing Foundations

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Old 05-08-09, 09:46 AM
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Mixing Foundations

Our home rests on top of concrete blocks which, in turn, rest on top of 24" X 24" X 2" pads. The pads sit on top of the dirt.

We want to replace the blocks with properly designed spot footings. That part I can figure out. There are plenty of references for how to design a spot footing.

The problem is, I need to be able to create the spot footings one at a time, over a long period of time, until they are all finished.

My question is this: If I create spot footings, can I come back later and "fill" in between them (around the outside of the house) with a continuous wall of concrete blocks?

When finished, it would basically be a continuous spread stem wall made of concrete blocks -- capable of supporting a second story addition.

Good idea? Bad idea? Overkill?
 
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Old 05-08-09, 08:43 PM
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The "spot" footers. Are you they concrete structural pads?

Just trying to get the lingo for both of us to understand things..

Is this a ranch home with conc pads under the house like a mobile home?

Also need to know exactly what the bottom of the out side floors are made of and is there already a house plate there and block piers every so often to help support the house.

Not trying to be picky. I can help here. Moved a house already and replace foundations and footers under houses not to mention been building foundations for over 30 years. Have done quite a few under pinnings on foundations also.

Are your skills in this area good? Reason I'm asking the "stem walls" aren't spoken of in that context. It sounds like you got the terminology off of a site...
 
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Old 05-11-09, 02:15 PM
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Hey, thanks for the interest.

I don't know if the concrete pads that the blocks sit on top of are "structural" pads. They are just flat, square pads (24 X 24 X 2). Saw similar ones at Lowe's.

I plan on building new piers. The ones that are there now look like what you would see under a mobile home. No mortar holding them together. No rebar. They sit on top of the dirt.

I realized after posting this, that I may be causing myself a lot of work for nothing. There is a sill beam that runs around the perimeter of the house and a girder that runs down the middle. (Just your basic rectangular house, about 36' X 24') If I create a solid wall around the perimeter, then there would be no reason for a sill beam -- it would be replaced by a sill plate. Problem is, if I do that, the house will come down about 8". That, of course, would screw up the plumbing.

I'm not sure a solid wall is worth it. I wanted a solid wall for longevity. I have seen plenty of old houses with solid walls around the foundation that are in great shape. The ones that I've seem with spot footings generally have problems.

If you have a better idea, let me know. I just have to do things very slowly, one step at a time.
 
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Old 05-14-09, 04:56 PM
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Is this a modular home" or a double wide"' What you are asking I have done before for a customer. He had a double wide and it was set up for a perimeter foundation. The difference is how the metal frame comes out to the perimeters. If its not set up for that then the last course of block needs cut many places. Also the middle beam/girder supports needs to remain. Don't quite under stand the 8" changing. Why would the height there change/
 
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Old 05-15-09, 06:22 AM
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Thanks 21 boat.

This might be confusing to explain. The house is a traditional stick construction with 2 X 4's. However, the foundation is the type you would find under a mobile home. I don't know why it was done that way.

The comment about lowering the house 8" comes from the way the house is currently "sitting" on top of the piers. (When I say sitting, that's what I mean. There are no connections. It is all gravity.) The floor is constructed as usual, with floor joist. Directly under the floor joist there is a beam made of two 2X8's. They are nailed together and create a perimeter around the outside of the house. Down the middle runs another beam constructed out of three 2X8s. The constructed beams literally "sit" on top of the piers and the floor joist literally "sit" on top of those.

If I put in a concrete perimeter wall, that "constructed" beam assembly would no longer be needed (except the one down the middle of the house). The square part of it (around the perimeter) would become a single 2X8 resting width ways on top of the new concrete wall (what I have been calling a sill plate). That would lower the house by maybe 7".
 
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