Jacking up a house is likely the most difficult do-it-yourself project imaginable. There are some realities about house jacking that make the project more difficult and complicated than it may seem. Not only that, jacking up a house safely takes a long time.
How to Jack up a House
- Holes are created in the foundation for the steel lifting beams. For masonry foundations, concrete blocks or bricks are removed to create holes.
- Steel beams are inserted through the holes. The beams run perpendicular to the house's own beams or joists.
- The second set of steel beams is inserted perpendicular to and underneath the first set.
- Screw jacks are placed under the steel beams. Supports are placed under the screw jacks to prevent them from sinking into soft ground.
- The jacks are raised a little bit, usually about 1/8-inch per day.
- Cribs, or wooden supports, are placed under the beams.
- Once again, the jacks are raised. This process of jacking and cribbing continues very slowly. The cribs are built up in perpendicular stacks.
- Eventually, the house is completely free of its foundation.
- If a new foundation wall needs to be built, for example, this is built after the house has finally reached its desired height.
- After the foundation has been built, jacking and cribbing are slowly done again, but this time in reverse.
- After the jacks are free, they are removed, along with all of the cribbing materials.
House Jacking Can Mean Different Things
While few of us are interested in jacking up an entire house, complete with cribs, girders, timbers, and everything else you need in order to lift a house off the ground, there are some do-it-yourselfers who may want to jack up a portion of the house in order to insert an extra tier or beam for repairs or to level an old, sloping floor.
Lifting an entire house into the air is completely out of the question for nearly all do-it-yourselfers. There's just too much that can go very wrong. If you don't know what you're doing, it's very risky for your house, and it's very dangerous for everyone involved.
Jacking up a corner of the house is another story. But there's still ample opportunity for you to cause significant damage, not to mention the potential danger.
Screw Jacks for House Lifting
An ordinary hydraulic jack is no match for a house. Take your strongest automotive jack from the garage and this jack will crumble under the weight of a house. More precisely, it will never even begin to lift.
Jacking a house typically is done with screw jacks and a lot of them. Screw jacks are manually turned with handles.
Hydraulic jacks are also supplementarily used. In any case, you would want at least 20-ton jacks, and 40-ton is better. You can rent heavy-duty jacks, but a rented hydraulic jack would be underneath the house for a very long time, running up charges, so you'd be better off owning them.
Parts of the House That Are Lifted
A house is constructed of thousands of pieces of lumber, nails, screws, wire, metal, masonry, and countless other types of building materials. All of these materials are interlocked, like a jigsaw puzzle.
Contrary to what one might expect, a house does not raise or lower like a giant box. Instead, a house raises or lowers more like a giant mattress.
Imagine going underneath a mattress and trying to lift any portion of it with your fist. Most of the mattress remains stock-still, completely unmoved by your efforts. Even areas of the mattress in the immediate vicinity of your hand barely move. It is only the portion of the mattress directly above your hands that rises. So it is with a house.
If you were to place a few hydraulic or screw jacks in close range beneath the house, then lift slowly, the results are disappointing. First, you hear the housing protest with cracks as loud as rifle shots. Joists groan. Upstairs, plaster and drywall crack and crumble and fall. Yet below, there is little sign of elevation.
If you plan to do any kind of raising and shoring of any portion of your house from beneath in a basement or crawl space, just keep in mind that you will not be able to influence more than a small portion. Even then, you will probably accomplish nothing more than replacing rotten timbers with new timbers or girders and maintaining the same slant of the floors above.
Speed and Amount House Can Be Lifted
As a general rule, a house—including any portion of a house—should be lifted no more than 1/8 inch per day. If you have to raise the house 1 inch, it will take at least eight days.
This slow pace gives all the interconnected materials a chance to settle into the new position without falling apart.
Presumably, the house started out square, plumb, and level, and it gradually settled over time so that it's gotten used to the new position.
Lowering the house goes slow, too.
Keeping the House Standing
Houses must be lifted using the same supports that keep the house standing, such as the carrying beams and the load-bearing walls. Knowing where to place jacks, how many to use, and how to distribute the pressure of each jack is critical to a safe and successful house raising.
Even if you understand home structures and which parts carry the loads, jacking a house is, in some ways, the reverse of those forces. So, conventional structural rules don't always apply. Knowing what to expect takes experience.
House Raising. International Association of Certified Home Inspectors.