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-   -   Inadequate center support in tight crawl space (http://www.diychatroom.com/f19/inadequate-center-support-tight-crawl-space-27471/)

4just1don 09-28-2008 09:48 AM

Inadequate center support in tight crawl space
 
I have 2 houses built identical ( LESS than quality construction,,,defined CHEAPO)in late 40's 50's era. VERY small,,,aprox. 20 by 28 foot rectangular one story homes,slate siding era, minimal eaves and overhangs. As I said they are VERY small. There is a center beam the length of the 28 feet that supports floor joists of the 20 ' width.

NOW the problem,,,whoever built them just put cement blocks on dirt with NO support under them. About 4 sets of them on 28' length. needless to say in very wet years OR plumbing gushers the crawl space got wet enough the blocks sunk into the dirt,,floors developed a sway of 3-4 inches. Been that way as long as I have owned them(at LEAST 30 years). Remodeling them now and need to level them up first. Crawl space is VERY tight and not easy to negotiate.

WOuld LOVE to pour concrete footers underneath BUT access hole of about 2 X 3' is right angle to crawl space and directly in front of a heat duct,,,read, hard to get crete in there anyway. Also understand I am NOT a small waisted gopher!! . Do You experts think another set of blocks between all the existing blocks,left on the dirt would spread the load enough to keep them from sinking,,and blocking more on top of existing piles of blocks.

IF not an option,how big and how deep would one need concrete poured? for proper support? It is good black sand and dirt ,topsoil, we have a white sand subsoil with NO rocks at all here in Nebraska with harsh winters BUT if it froze in this crawl space plumbing would be toast anyway!!(so doubt freezing or heaving is an issue)

Anything else I could get in there to support the blocks??

This isnt a GOOD situation,,just want to make the best of it the easiest. ANY feedback appreciated!!-d-

Termite 09-28-2008 10:07 AM

Tough situation for sure. I'll take your word for it that freezing isn't an issue in the crawlspace. Normally I'd advise frost footings anyway.

Is the 28' beam deflecting noticeably? You mentioned a 3-4" "sway" in the floors, but I'm not sure what you mean. I'm assuming that you mean that the floors are sagging at some point due to beam sag/deflection. If so, how are you dealing with that? Jacks? Or, has the soil under the blocks become undermined and you're trying to prevent the beam from deflecting?

Adding blocks is certainly better that what you have now, right?!?! I'd still try to find a way to get some concrete under there. Pouring a 12" thick pad under the blocks perhaps 24x24" (minimum) would spread the load out nicely. You'd be crazy not to throw a few sticks of rebar in the pads, running in two directions. It would be expensive to have the concrete pumped, but would make it a lot easier. Otherwise you'll have to use a wagon, tubs, or buckets to get the mixed concrete down there.

4just1don 09-28-2008 10:38 AM

KC,
My bad,,,yes the beam is deflected 3-4 inches( a guess) and looks like the old sway back mare,,allowing the area of the kitchen cupboards to sag the worst, other end with bedroom /living room sags LESS. BOTH houses sag exactly the same. Would like to plop a posy of dandelions on the guy's headstone who did what he did,,,placed blocks on bare dirt,,,dont know WHO it was so out of luck on that account.

After I posted that I recalled I am going to replace the peach crate cabinets in one unit anyway. You would be surprised how many OLD hand built cabinets were made from peach crate material,,,or similiar(doors and drawers dont work too well) May take cabinets up and cut a temp hole in floor to 'pour' cement thru,,,that would get me HALF way there,,,biggest prob is I wasnt going to do other units cabinets yet,,,BUT maybe I will now,,,or at least cut a temp hole thru the bottom.(and build a chute)

I jacked the easy to get at house up in two places last night,,,jacked up easy,,but of course didnt go all the way,,yet,,,easy does it,,took a long time down,,few days back up!! Going to go string it end to end to see where level really is.

Local concrete place has plastic half barrels I can throw in back of pickup,,,they fill them in there out of a larger batch to someone else. How much would it take for say 5 pads per house?? Supose could do one house at a time. THANKS-d-

Termite 09-28-2008 10:48 AM

Well, there's 27 cubic feet of concrete per cubic yard. The size of pads I suggested would take 4 cubic feet each. That's about six or seven 80 pound quickrete sacks per pad if you go that route.

Like I said be sure to add some rebar. You can cut it into short pieces with a grinder and cutoff wheel or a circular saw with an abrasive blade.

The safest, smartest thing to do would be to have an engineer size the pads for you. All I can do is guess based on the size of the house and the number of pads on the beam....And it is just a guess. But, anything is better than what you had.

Termite 09-28-2008 10:50 AM

Remember that wet concrete weighs between 110 and 120 pounds per cubic foot. So, don't overload that pickup truck! Besides, you don't want that concrete sitting too long before you place it, so don't bite off too much at once time.

buletbob 09-28-2008 03:29 PM

Quote:

Originally Posted by thekctermite (Post 161917)
Remember that wet concrete weighs between 110 and 120 pounds per cubic foot. So, don't overload that pickup truck! Besides, you don't want that concrete sitting too long before you place it, so don't bite off too much at once time.

If its in a small crawl space now i was going to suggest opening the floor up so you can dig and pour your pads, 1'x2'x2' with re bar will be plenty for a one floor ranch. just make sure you get to virgin soil.


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