Load Bearing over Flat Roof of Room Addition

bixmeisterFebruary 8, 2010

I own a house in El Cajon, CA-near San Diego. I recently came up with a scheme to use rainwater in my nearby garden. I have collected 110 gallons of water in 2 rain barrels from an overnight 1 1/2 inch rain fall. We have had a lot more rain recently but my barrels are at capacity.

I built a stand for my 2 55 gallon barrels and the combined weight of 918.5. The stand is built from 4 X 4s and 2 pressure treated plywood for the top surface. The plywood is 1/2 inch thick(I doubled them up for better weight bearing. I checked the stand after the rains and the stand is holding up fine with no sagging or other problem indications.

My scheme is to purchase a 275 gallon rectangular Tote. The Tote is 48" long by 39" wide. I calculated the pounds per square inch to be1.22662927.

The load pressure for my 55 gallons is 1.208130704.

You will notice that the load stats are very close between the rain barrels and the 275 gallon tote.

My question is based on what I relate do you think a tote situated at a corner just above my drain pipe(sitting above corner joists) would be a safe load). The tote will be supported by normally spaced studs. My rain barrels only had support from the outside periphery of the 4 X 8 top surface(no center support) yet no sign of sagging or stress.

I am not a carpenter or contractor. I need to decide soon, before the next rain whether to go ahead on my scheme. Rain will be coming according to forecasts.

Horace Bixby

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I can't answer your question technically, but I can say that I wouldn't chance it. You'll be putting 2300 lbs of water in that one area with no idea of how the structure is built underneath. Plus, if this is a flat roof, wouldn't you be taking a chance of damaging whatever surface you have on the roof?

When we built a barn last year the contractor had to reinforce the joists in an attic space so that a 55 gal. tank (for fly spray) could be placed there. And that was for only 460 lbs.

I'm assuming the structure holding the barrels is sitting on solid ground, which is why you're not seeing any give. Plus, it's sitting on 4x4's.

I think you'd be better off finding some place on ground level for your tote.

    Bookmark   February 11, 2010 at 7:13PM
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it's obviously a serious overload to the roof structure. Good luck.

    Bookmark   February 13, 2010 at 5:32PM
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