# Pouring foundation under existing structure



## Downriver Tackle (Dec 24, 2004)

Whacky project.

Have a mud room on the place I bought up North that's treated lumber on the ground for a foundation. Without tearing it off and restarting, because the structure is absolutely fine, I want to put cement under at least the perimeter of the walls and in a few feet. I have a plan with taking out the floor, trenching around it, jacking it up a little, making forms, pouring the concrete w/footing, and then lowering it back down and securing it to the concrete. Looking for any hints or ideas. Am I crazy? LOL


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## Jekart (Apr 27, 2006)

One question.....why? Is there an issue with the current treated wood foundation?? 

If your intent is just to put down a better footing, I would look at using posts. If I am picturing this in my head right (and I may not be), it would save you a lot of time and money.


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## Big Reds (Oct 14, 2007)

From what I gather from your post, the rim board is laying on the ground? If so, you may be better off re enforcing the rim board and cementing in posts. Much easier, less time, and less money.
When you start jacking foundations, you could open up a whole new can of worms.


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## Rumajz (Dec 29, 2005)

I've done it a few times. Used Insulated concrete forms and it worked out fine (but Big Reds is right). If you really want a concrete foundation under it, ICF is the way to go.


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## Downriver Tackle (Dec 24, 2004)

I want to get it off the ground because it stays really moist in the area and the rim boards have been replaced once by the previous owner already. 

My question about the ICF is, won't that be a royal pain to try and fill completely in the very milited area I have to work with? And, will that small perimeter be able to support a load and not crack, which is why I wanted to go footings and pour it in a few feet? The current set up is slowly sinking into the ground and is throwing everything off-square, like the entrance door.


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## Rumajz (Dec 29, 2005)

Sorry man, I must have been half asleep when I read your post. I think I know what you meant now. 
If frost moving your structure is not a concern and you don't need an inspection, your concrete slab with a shallow footing will be better than what you got now. I would use a 6 mil plastic under the whole thing though. Otherwise the moisture problem won't go away. 
I've only done either full foundation basement walls on footings or crawl space walls on footings under existing structures. There always was an access under the structure and it was necessary to raise the structure by at least 6". It was still a pain in the butt to get the concrete in there but the ICF's made the process a lot easier. 
Definitely not an easy money job for sure.


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