Re: Floor sags in center of home
Pictures of the support structure would be helpful .... also if there is a basement or crawl space underneath.
Typically there is usually a main carrying beam that runs down the center of your home in place which the floor joists rest on and secured to.
The ends of the beam would sit on the foundation and usually have support columns in place to support the loads placed on this beam along the mid-span ... unless the main carry beam is a steel "I" beam designed to be free span without support columns.
The support columns can be a variety of different configurations depending on area .... brick , concrete filled steel pipe , adjustable steel columns (telepost) , solid wood posts ....... regardless which type will rest on some type of concrete footing..... either individual concrete pads 24" x 24" x 12" , 30" x 30" x 12" or a continuous concrete grade beam.
From your description there seems to be some settling ... for whatever reason.... along the mid-span. If you were to run a tightly stretched string line from one end of the support beam to the other this would provide you with a reference line.
On each end set the distance from the bottom of the beam to the string to a known value .... 2 inches for example. Now measure the distance from the bottom of the beam to the string along the center and you will likely notice the measurement to be less indicating how far it has sagged and how much it needs to be raised.
When raising up .... resist the temptation to do it all at once and do it gradually ... if you do it all at once you will likely have cracks appear on the walls upstairs.
If you have the adjustable columns in place your off to the races ... simply turn the threaded rod counterclockwise to extend it for raising .... remember a little at a time ..... perhaps a 1/4 turn over a course of a month.
If the existing columns are not adjustable you may be able to purchase the steel teleposts ( which are reasonably priced) and use those or screw jacks to raise the support beam. It's important to ensure there is an appropriate base under whatever is being used for jacking. Place a steel plate under whatever is being used for jacking sitting on a pair of 4x4 or 6x6 at least 2 feet long ..... this will help in displacing the weight.
Don't simply rest the jacks on the concrete floor ( if there is one) it's not meant to carry that weight.
Once the beam is in the correct position appropriate spacers or shims can be used between the columns and beam.
A general contractor or foundation contractor could do this for you as well.
These are general points .... if you are unsure as to what you are doing .... there is some question as to the beam may have failed .... or .... the columns are sinking .... then a professional should be consulted.
Here is a link on a previous discussion that may be useful : http://advice.thisoldhouse.com/showthread.php?t=1592
Hope this helps.
Last edited by canuk; 06-15-2008 at 08:20 AM.
"" an ounce of perception -- a pound of obscure "