New Pier & Beam construction, can I leave the old home slab in place?

Started by timsch, December 01, 2017, 09:44:17 AM

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timsch

I'm tearing down an old house and plan to build a new pier & beam house on the same location, with a nearly identical footprint.  The new house will be about 4ft higher than the current one.  The old house can be demo'd by itself, or I can demo both the slab and home.

What are the requirements for the ground under the P&B home, other than water must not pool underneath?  We can cut through the slab as needed to place footings for the piers and are not planning on supporting the new home on the slab in any way.  I'd rather crawl around on concrete underneath the home rather than on dirt.  Is this an option?

Thanks.

ChugiakTinkerer

Welcome to the forum!

If you share a little more info about where the house is located and why you need to elevate it you'll probably get more topical and relevant replies.  Presumably there's a jurisdictional authority such as the county building inspector that will have the controlling opinion on how you should build.  I'm no code expert, really just a guy on the internet, but as long as the piers are not enclosed there's probably nothing in the code that would require one surface or another under your new house.  If it is enclosed as a crawl space then managing moisture and temperature might be a concern.

When it comes to pier foundations, they are not prescribed in the residential code.  If you've got an engineer involved that is licensed in your state you should be good to go.  Again, the building inspector will let you know what they will approve.  Hopefully you're already engaged with that department as needed.
My cabin build thread: Alaskan remote 16x28 1.5 story


timsch

Thanks for the welcome.

The house is to be located in a 100 year flood plain in the Houston area.  It is replacing a slab house that flooded.  New construction in this flood plain must be 2' above base flood elevation.  I'm building the new house at that elevation.  We chose pier & beam for multiple reasons, the main ones being that we would not have to bring in the quantity of fill needed to raise us up 4', and the flexibility of leveling and/or raising in the future that is more difficult with a slab foundation.

We are in contact with the city inspector.  I haven't asked him specifically about this yet.  We are in the early stages of planning for the build.  We have purchased plans from an online source, but have not had them looked at by a local engineer or other authority.

MountainDon

I believe the Houston area has a lot of clay in the soil. That is bad news if true as when wet it offers little lateral stability. When dry it shrinks and wet wet it expands. I would immediately ask the local building department what the rules call for before spending much time on any kind of planning. I'm fairly certain that the piers used in coastal clay soil areas and be 15 feet deep or deeper. I have noticed in the past that the coastal areas of TX have large numbers of foundations contractors who specialize in various pier or piling foundations.

Just because something has been done and has not failed, doesn't mean it is good design.