Jack Post support question

I dug 3 holes in the crawlspace under my kitchen to help support a floor that I found out sagged when we had the kitchen ripped out & redone. It's a total span of 8 feet. The circular holes are about 18" deep & 18" in diameter. I wa splanning on filling then with concrete then buying 3 of the small size jack posts that HD sells and placing two 8 foot 2x6 beams on them.
My question is does it matter if the wood beams lie flat on the support posts or on their bottom edge?
Also how many pounds of concrete would it take to fill the 3 holes? thanks
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saag wrote:

If you intend to lay the 2 x 6's flat you will effectively have 3 1/2" to support the floor. Doesn't it seem more logical to have a full 5 1/2" support the other way? Nail the 2 x 6's together, naturally.

Do the math: most Quickicrete or whatever is .8 cu ft. per bag. So 3 1/2 bags would be about right. YMMV.
Joe
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If you lay them flat, they will flex and the floor will sag again. Put them on edge.

You can also fill with some rock to take up some of the void. Better yet, use a Sonotube in the hole and fill around it with dirt. That can save lugging a couple hundred pounds of concrete mix. To calculate the volume Pi x r2 x h The way you are set up now, you'll be lugging about 800 pounds of the stuff. Using a 10" tube you can cut that down to about 250 or so.
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Thanks. I'm not raising the floor. I'm just looking to support it from sagging further from things like snow/ice on the roof etc. I didn't become aware of the problem until we had the kitchen floor ripped up and replaced. The new kitchen is already in. It's level now so raising the floor could mess things up.
The crawl space under the kitchen is only 2 feet high. Would solid cinder blocks also work as opposed to an adjustable jack post? I would think that would be better support but then I'd have to worry about making it the right height to fit the wood beam sin snugly whereas an adjustable post would make that part easier.
I also have a lot of small stone in the garage that I was thinking of dumping in the holes around the concrete tube forms rather than dirt. Is it ok to leave the forms in the ground?
Edwin Pawlowski wrote:

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Blocks would work. It may be possible to set them in place and somehow shim them the last inch or two. Since yo are not tryhing to raise the floor, a snug fit of a 2 c 4 would be sufficient. It would stop downard movement and that is your concern now.

Yes and yes. Just be sure to pack in the stone as best you can.
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Has anyone ever used this brand? They sell a model that extends from 19 inches to 3ft.
These posts seem to work by inserting a smaller tube into a larger one then bolting them together. Then turning a screw to fine adjust the height. The screw must adjust it only to a certain level before you'd have to bolt the smaller tube higher. I've read some info that says these posts aren't meant to be used permanently.
With the height of the post plus the height of the wood, I only need the min height of the post so I'd never be changing the bolt positions - both tubes would be resting on the concrete pad. So I was wondering if I could fill the tube with concrete up the the level wherever the screw reaches. If I fill my foundation hole with cement up to the level where the post height & the wood height gets me to a 1/4 inch or so I could then use the screw for the final height adjustment. Maybe that would make the post more viable to be used permanently. After the final adjustments were done maybe I could fill in the rest of tube with concrete. This may be easier than trying to shim in wood if I use cinder blocks.
I was wondering if that would actually work with this particular post.
Edwin Pawlowski wrote:

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I have a pair of the taller model Tiger jackpost. Each unit consists of a threaded section that sits on one end of the pair of tubes which have holes through which a pin controls their total length in increments of several inches. This whole apparatus has a top plate and a bottom plate of fairly thin metal - they only stay in place by gravity. The threaded section just slides into the tube by gravity as well. I would consider them to be temporary supports and not super-stable at that. Any lateral movement and they fall over. They are not a Lalley column.
For permanent install, I would get drill stem (2-7/8 diameter, 0.25" wall drilling pipe) and weld steel plates on each end (3/8" or better thickness). Drill holes in each plate and lag to the beam and floor.

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thanks for that info. That''s a little involved for me so I think I'll try the cinder block approach first.
Tom Kendrick wrote:

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