# How much weight can floor made of plywood over joists on concrete slab support?



## Nospammer (Jun 16, 2011)

I'm installing a 3' x 4' masonry heater that will weigh 1700 - 2000 lbs in a room that is a converted garage. The floor is plywood over 2x4 joists directly atop a concrete slab. 
How much weight can this type of floor support?


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## joecaption (Nov 30, 2011)

How thick is the plywood?
The concrete and 2 X 4's are fine it's the point loading on the plywood just trying to get it in I'd be concerned with.
Anything with wheels may just break through the plywood.


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## Nospammer (Jun 16, 2011)

i think it's 3/4" plywood. the heater will be mostly made of bricks like this: http://donkey32.proboards.com/thread/803/evaluating-6-dragon-burner


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## oh'mike (Sep 18, 2009)

How about cutting out the plywood and framing in that section--then constructing the new heater right on the concrete slab?


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## Nospammer (Jun 16, 2011)

Thanks, but I won't be cutting into the floor as this is the spot it will be housed temporarily to test how well it runs this season. Then, I'll be having to deal with supporting it in it's new spot in the LR where there's pier and beam flooring over a crawl space which is probably 12-18" high.

How much can this *floor made of plywood over joists on concrete slab support?*


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## alexjoe (Jun 10, 2013)

Cutting into the floor is not a good solution of this problem. You can simply test out this.


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## Daniel Holzman (Mar 10, 2009)

The TECO website discusses calculation of allowable load on plywood, here is the link http://www.tecotested.com/techtips/pdf/tt_plywooddesigncapacities.


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## Oso954 (Jun 23, 2012)

As far as I know, rocket mass heaters do not pass code, and insurance companies do not insure houses with them.


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