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Raising A House 3 Feet

Editor's Note: This is material of a highly risky nature. Do not consider this as "instructions"; this is for entertainment value only. If not done properly, lifting a house can lead to personal destruction as well as financial ruin. Read our Disclaimer.

 

Question:


I just finished reading your article on lifting houses "Raising Part of A House" and I must say it was very interesting. I am currently in the process of lifting a home I recently purchased. I won't drag this out with all of the details of my home but I do have a couple of questions for you in reference to some of your recommendations.

The first question is in reference to your suggestion of lifting a home only an 1/8 inch per day. This makes sense to me if a guy is trying to prevent damage to sheetrock and or plaster but what if the home is totally gutted? Is there any reason why I can't go up 3 feet in a day or two?

My second question is in reference to items used in the lifting process. I've read several articles on lifting homes before I started my project and found that most contractors like to use the method of lifting you outlined. I being a newbie to this level of construction found the method you use a little scary. I opted to use 4x6 beams cut into 2-foot sections and cross stacked as cribbing. I then place the screw jack atop the cribbing. I'm sure it cost me a few hundred dollars more for this method but I feel more secure when lifting my home with cribbing. Finally for my question, is the cribbing method I'm using overkill in your opinion? I haven't started the 3-foot lift yet and to do it I will need to buy a lot more 4x6's to do the job. The home is a 1924 farmhouse, redwood construction and completely gutted on the inside.

My last question is in reference to a general review of my planned attack of the project as follows: Since the home is now mostly level, I want to install new stronger girders in place of the old sagging redwood girders. I then plan to lift from the new girders as well as from 4x10 needle beams placed under the floor joists alongside the sill plates. Finally I plan to support the home with framing rather then use posts as was done before. I'm always open to suggestions so if you see any glaring mistakes in my plan please drop me a note

Background on my little project: I started this project of lifting the home to level it, then decided to install a full perimeter foundation (installed footing and 8" stemwall for a two story) now I'm planning on raising the home an additional 3 feet to make the lower floor a full 9 feet, floor to ceiling.

Thanks for taking the time to read over my questions. 
John

 

Reply:


Heck, you can lift a house 3 feet in a minute, if you can muster the horsepower. The 1/8 inch per day is an old rule of thumb I first heard in college 20 years ago, and it applies to houses with drywall or plaster that is meant to be saved.

You are right about using cribbing for a whole-house lift. My article doesn't show cribbing because when lifting the center of a house, the middle of a floor, or a corner of a house there is no risk of the structure falling over sideways. But when you raise a structure completely off it's foundation, there is no longer any friction to prevent it from sliding sideways. In this case a very stable base is needed. Think pyramidal. A pyramid is an inherently stable structure. (Have you ever seen a pyramid fall over? No. I thought so!) If you build your cribbing with an extremely wide base (perhaps 6 feet) with a less-wide top (perhaps 2 feet or a bit less) then there should be little or no risk of the structure shifting sideways. But... here's the clincher... technically you only need one or two of these highly-stable supporting structures (unless the house splits apart during the lift) and the others could be less-stable supports, such as narrow cribbing (entirely 2' square, non-pyramidal) or even simple lally columns. Personally, I wouldn't use lally columns for anything but "interstitial" supports, that is, supports in between highly-stable cribbing supports. You could spend a fortune on wood for cribbing.

Another thing: One article I read (This Old House magazine, I think) mentioned using 6x6 blocks of oak for cribbing. This would be an investment akin to a king's ransom, unless you had some oak trees in your backyard. Oak is extremely hard and resistant to crushing, which is the reason they use it. But Southern Yellow Pine is about half as hard as oak, yet twice as hard as typical spruce/pine/fir lumber.

About that 4x10 "needle" beam. (I've never heard that term, but I've wondered if there was a word for such a beam parallel to the sill.) I would consider something heavier, unless you plan on placing supports every 5 to 6 feet under this beam. I would try using triple 2x12's nailed or bolted together, then the supporting structures could be placed farther apart, maybe 8 or 10 feet on center.

Which brings me to the important issue: Beam sizing and support spacing. This is a highly technical topic that requires some understanding of engineering. I recently wrote an article about replacing a beam in a porch roof, and I went into a discussion of determining the size of a beam. Beam sizing and span (which dictates the spacing of the supporting posts or cribbing) depends on many factors, such as 

  • The width of the building, 
  • The number of stories, 
  • The presence of a center-bearing wall (many old houses used this technique) and 
  • The live load on the roof. 

This last factor is not important because you can choose to do this work when there is no chance of snow... although there is always a chance of wind, which can cause some loading problems. Anyway, you can use the best-case roof live load of 20 pounds per square foot, which allows you to use longer spans for your needle-beams and center beam.

One handy reference book I looked at is "The U.S. Span Book For Major Lumber Species" published by the Canadian Wood Council. Apparently they have a web site with an online span calculator. I haven't looked at this site, but the little handbook is pretty easy to follow.

You seem to be on the right track.


Bruce W. Maki, Editor.

 

 

 


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Compiled May 13, 2002