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Sagging floors


We purchased a home from the 20's or 30's. It's two story plus a full attic, and a finished basment with a sub-basement with about 4' of height in most areas.

The floors are sagging toward the middle of the house from front to back, on the back half of the house.

Does anyone know how I can determine if the beams in the sub-basment are sagging? There are screw type ajustable posts that are planted in 5 gallon buckets of concrete buired in the dirt (former owner did this).

I remember seeing on This Old House where Tom Silva showed how to tie a string from one end of the room to the other and with a sting level you could figure out where to jack the beam. The problem is, I don't remember the specifics of how to do this. Does anyone know what I'm talking about?



Re: Sagging floors

Does anyone know how I can determine if the beams in the sub-basment are sagging? There are screw type ajustable posts that are planted in 5 gallon buckets of concrete buired in the dirt (former owner did this).

I'd put a bet on the beam is dropping down. These are nowhere near the proper footing for the support posts. These are probably just sinking into the ground therefore the beam is following.

I suggest calling in a professional to have a look. The footings would likely have to be properly sized (possibly 24 inches x 24 inches x 12 inches or larger) and installed under the support columns. The spacing of the columns and the size of the beam is unknown and should also be checked.

Re: Sagging floors

Another point, the screw jacks are made for temporary use not permanent support. Permanent posts should be concrete filled posts.

Re: Sagging floors

Not to get too far of topic ...

Jack ,
I believe the adjustable single steel columns are accepted in areas and can remain hollow without being filled with concrete.

Aren't these columns called lallys? Well, yes. I've heard that term used a lot. Lally columns or lolly columns are terms that are widely used in my area (Hudson Valley, NY) for any steel column. The terms also appear in various construction dictionaries. Originally a Lally Column was a proprietary name for the concrete filled steel column invented by John Lally. Many people feel that the term should only be spelled “Lally” and that it should only be applied to concrete filled steel columns. Perhaps they're right. But, of course, language is fluid and in this case the popular use may have become the accepted use. "

This is based on a report I read from the American Society of Home Inspectors (ASHI).

"In new buildings and in new construction, you may find that the single tube adjustable column is labeled with a reference to an ICC-ES Report, a BOCA Report or a CCMC Evaluation. This means that it has been independently evaluated and found fit for permanent structural use. If It's manufactured for use in the U.S. it will cite an ICC-ES Legacy Report (issued by the International Code Council Evaluation Service), or a BOCA (Building Officials and Code Administrators) Report."

Here's an example of the one piece hollow units.
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Now the two piece adjustable ones seem to be not allowed for permanent use.

"The telescoping columns come in two or more hollow steel tube sections that are assembled on site. That is, the smaller diameter tube is fitted into the larger diameter tube and the sections are held in place with steel supporting pins which pass through the pre-drilled holes of both tubes. The adjusting screw is assembled at the column's smaller diameter end. "

"Telescopic adjustable columns are regularly used in construction to adjust or level a structure before installing a permanent column. Or, they're used as temporary supports during the course of a building repair. But many inspectors in the U.S. encounter these telescopic columns in permanent use. This is a defect because no telescopic adjustable column has been evaluated by a U.S. evaluation firm and none of their manufacturers cite an engineering report to prove these columns' ability to carry a specific load. Also, according to the IRC, a steel column has to be at least 3 inches in diameter. All telescopic columns are all less than 3 inches in diameter. You must therefore assume that these adjustable columns are not designed for permanent structural use. Think of these telescopic columns the way you would think of a car jack. They only exist to temporarily "jack up" a part of a building and should be replaced with a permanent column when the jacking up is done."

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Now up here adjustable columns are used quite a bit for permanent use. Even the two piece units have approval which I don't like to use. I prefer the solid one piece units myself and only use the two piece for temporary use even though they are approved for permanent use.

Anyways ... back to our regularly scheduled program.:)

Re: Sagging floors
canuk wrote:

I suggest calling in a professional to have a look. The footings would likely have to be properly sized (possibly 24 inches x 24 inches x 12 inches or larger) and installed under the support columns. The spacing of the columns and the size of the beam is unknown and should also be checked.

What kind of professional would you suggest. A structural engineer? Any estimate on what I should expect this to cost? When I searched yellowpages.com for structural engineer I only found one.



Re: Sagging floors

A structural engineer would definitely be sufficient. How much they would charge depends on them. I've had them charge anywhere from $250 -$500 for an evaluation depending on the scope of what they will include such as a written report and/or drawings.

You can contact a General Contractor but they may be required to have an engineered drawing for the work anyways.

Contact your local municipal building permits department they would either suggest someone or at least what avenues you can take.


Re: Sagging floors

Canuk is correct.

I did this job ten years ago as part of a partial cellar excavation, on a house such as yours, of similar size.

The town made me hire a civil engineer (Yellow Pages, "Engineers, Civil) to draw up plans of how to go about it before they would give me a permit.

Thankfully, they allowed me and my crew to do the work; the engineer cost $500, but he was good & visited the site several times & offered great advice.

The first step is to get the floors & beams level & plumb; as you noted, take a nylon string & tightly stretch it the length of each floor & along the lower beams, & use a little line level to get the string plumb.

You should immediately be able to tell how many inches out of line not only the basement beam is, but also the floors & attic above.

The beams of a house are like the old bones of an aged elephant; they often creak & moan when jacked back into place; don't expect perfect symmetry.

It's ok if the plumb is a little off after a month of jacking, as long as it's not too noticeable on the floors.

Also, go out in the street or your yard & visually check the horizontal line along the roof peak; there should be very little or no apparent bend in it.

The adjustable posts should be placed on firm footings or heavy rocks every 4' to 6' and cranked GRADUALLY a few turns a day to get the beam & floors level.

This will take a month or so if done properly, so the ceiling & wall plaster doesn't crack.

Remember the building's been slowly sagging for years & has to be brought back to plumb gradually.

The adjustable posts are only $10-$15 each & come in different lengths; they can be cut with the same circular saw blade you're using on the cast iron sewer pipes if you need a short one to use in the sub-basement.

Individual concrete pads are rejected in favor of a single steel-reinforced strip concrete 2' wide X 1' deep footing running the entire length of the house along the entire length of the sag.

Steel 3/4" rebar (at least 4 continuous pieces) is used in the new footing as the reinforcement.

Since the adjustable posts are in the way of pouring the footing, one or two posts are temporarily removed & the footing is poured in 6' increments with the rebar sticking 2 feet out the end of the pour with a keyway so the subsequent footing pour CAN BE TIED TO THE PREVIOUS POUR, & interlocks with the keyway and the steel rebar.

This interlocking tying in of each steel-reinforced subsequent footing pour is the key to a firm footing that won't crack or sag.

If there is a cellar window near the street this procedure is much easier if a concrete ready mix truck can simply extend his chute into the cellar & pour directly into the footing forms.

The removed adjustable posts are put back in position after the concrete cures (2 days), & the next footing pour using the same subsequent method is executed.

The new footing is then built up to the existing beam using solid concrete block masonry.

A sill of pressure treated 2 X 6 or 2 X 8 is used between the new concrete block & the wood beam.

Re: Sagging floors

JacktheShack ... nice write-up ;) :)

Re: Sagging floors

Thanks for a great deal of information that will help a lot.

One question I have is when I get the footing poured and start to build the block wall on top of it, how do get the right height out of the blocks to come to a point where you can place the wood on top to contact the beam? Do you end up cutting the top blocks to just the right height?

It may be all in your previous response, but I'm not getting it for some reason.

I am concered also that the existing beam is too old to be counted on. If you or anyone else is interested, I'll post some pictures of some of the funky foundation work that has been done by previous owners. About as wierd as the radiator work I mentioned in the heating group.


Re: Sagging floors

Yes, I'd like to see more photos of the beams & foundation.

There's a limit as to how much evaluation can be done over the internet; that's why it's usually so important to have an expert come over to take an on-spot look at it.

It's usually not necessary to cut the concrete masonry blocks, as you build up to the beam.

Controlling the amount of mortar in the final rows is usually enough to get a tight fit.

Also, the pressure treated sill can be double or triple layered using staggered joints to get a tight fit & maintain strength & good appearance.

If the main beam is dry rotted, 6' sections of it at a time can be cut out, while maintaining the adjustable jacks in place along the rest of the beam.

The new beam is lap-jointed or mortise & tenon jointed to interlock with each other if several sections have to be replaced.

I've seen these beams at Home Depot/Lowe's.

Moving structural wood with adjustable jacks is not that difficult.

Wood support beams, even if 70 years old, still have some elasticity.

A big issue is do you have adequate room to work, or how much finished basement or sub-basement do you have to remove before you have room to work.

It's a lot of physical work to do if you have limited or no help, especially mixing concrete & pouring footings.

Another issue is getting approval from the town if you want to diy.

Each town has its own policy on this issue; they usually insist on drawings & plans from a civil engineer, but they often insist that a contractor experienced in structural work do the job.

AS long as the building weight is transmitted to solid steel & concrete, then to the earth, the building should stand for hundreds of years.

Re: Sagging floors

Here's an example where I had removed the solid 6x8 wood posts and replaced them with steel adjustable columns. I had fabricated them myself and secured them to the footing piers with concrete anchor bolts ... with the blessing of the building inspector.


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