Q&A / 

Replace A Foundation

house having new foundation

Replace a Foundation | This house is being restored and a new foundation is on the to-do list. Copyright 2020 Tim Carter

Replace A Foundation - Just Lift Up the House

QUESTION: I’m thinking of buying a house that has a crawlspace. The foundation is in very bad shape. While the house looks quite bad, it’s got good bones. Is it possible to completely remove a bad foundation and install a new taller one? What’s involved? Who does this type of work? What would you make sure gets done if you’re going to all this work? Hanna S., Hartford, CT

Hanna needs to negotiate a really good deal on this dilapidated house. The good news is the old foundation can be removed and replaced with a new cast-concrete foundation creating a full basement. The task is not much different than eating an elephant. You just take one bite at a time.

Moving an Entire Neighborhood of Houses

Hanna’s question reminded me of a fascinating time early in my building career. Fresh out of college, I had just rehabbed my first house in Cincinnati, Ohio. It didn’t need a new foundation, but it was otherwise in pretty bad shape. Four months of work transformed the house back into its former glory.

About a half-mile away, a developer wanted to put in a small shopping mall, but there were about ten houses and an apartment building in the way. Not only did he buy all these properties, but he proceeded to move them about a mile away on some wooded land he purchased at the end of a street. I remember watching these houses, and parts of houses that were cut in half, creeping down the road to their new foundations.

Hanna needs to contact different foundation contractors to see which ones have done exactly what she wants to do. Not all foundation contractors have the expertise to work underneath a house that’s suspended above the work site sitting on cribbing made with timbers the size of railroad ties.

These foundation contractors will also know the names of the different house-moving companies in the area. The first step in the process of tearing out the old foundation and installing the new one is to prepare the house as if it’s going to be moved to a new location. House-moving companies do this like you might brush your teeth. It’s just another job for them.

Lift the House High Enough

I’d consider several things if this were my job. For starters, I’d want to make sure the house was lifted high enough so there was positive drainage away from all sides of the house. The building code’s minimum standard is 6 inches of fall in the ground in the first 10 feet of horizontal distance away from the foundation. I feel 12 inches of fall is much better.

Create a True Full-Height Basement

If the budget allows, I’d also try to pour the new foundation walls as high as possible so a true 8-foot ceiling height might be achieved in the basement. Hanna needs to make sure a great high-performance vapor barrier is installed under the new basement concrete floor.

To lift an entire floor, you'll have to jack up floor joists. Pros do this by sliding large I-beams under the joists so all the joists go up at the same time and same rate.

Install a Radon-Capture System

I’d also install interconnected perforated 4-inch pipes beneath the new basement slab to capture radon gas that might be seeping up from the local bedrock. A riser pipe that connects to the below-slab pipes should then be extended up to the roof to vent the radon.

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