twan5

Anyone have experience using these things?

My dining room is about 10'-12' wide and it seems that after 80+ years of previous families having dinner on their nice big heavy tables, the dining room floor has developed a pretty good sag. So much so that when I walk across the dining room, there is a nice little bounce to my step! There are other places in the basement where previous owners have installed these jacks, and you can tell because the areas/rooms that they have been installed under are very solid.

Do I need to take any special precautions or purchase any special machines or tools (other than the jacks themselves) to accomplish this? Any suggestions on how to do it?

Thanks!

Charlatan

If your floor is solid then all you really need are the jacks.

However, you should have a proper contractor look at your joists... They might be sagging for reasons like rot or termites... In which case, floors jacks aren't going to do anything but delay the inevitable.

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kazoo

It sounds as though either there is deterioration of the joists as pointed out above, or the sizing of the joists isn't up to spec. You can check this online by visiting www.cwc.ca and clicking the calculator under online tools.

When correcting sags, ensure that you use a sufficient number of jacks to distribute the load. When columns are planned for in a basement, a pocket of extra concrete is placed where the column will go. Jacks located at random will bear on the ordinary slab thickness and can cause cracking of the slab-hence my statement regarding load distribution. Otherwise, the only other precaution is to go slowly. The floor did not arrive at the present state overnight, and so your corrections must be made over time to preclude cracking plaster and overstressing joints. My personal rule of thumb is to not exceed 1/2 turn per day on the jackscrew.
Thusfar, that has proven successful for sag corrections I've performed on a number of dwellings.

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jbrooks544

If the joists are only spanning 10 - 12 feet then they must be pretty small to be sagging and bouncing that much. Could be a sign of rot or insects. If you don't need the space in basement (assuming rot or insect problem has been investigated and/or fixed) then you can go with posts(jacks). If you need the space to be post-free then you can add a girder beam or just sister (double)every joist or two. If you use your jacks then get a nice beam chunk that will span all the affected joists at their mid span point. Put a post (jack) about 1/3 of the way in from each end. That way, as long as your beam is sized correctly, two jacks will hold whole floor section up. Basically this is installing a girder beam in a fashion. If you don't cut slab, dig out and pour proper footings then you might use steel plates or another beam lying on the consrete to spread the load. The posts would rest on it and spread the load. Pad would have to be fairly large or just use a beam on the floor as a sort of "grade beam". Posts would bear on this (bottom sets on it). the only other thing is to be very sure to attach everything very securely. I would use nails or probably screws (at least) to hold every piece of wood and post (jack). Assume that all will fall apart and down otherwise. I might use use "sipson" (or is it simpson) ties, available at any bldg. ctr. to fully secure, especially in earthquake zone.