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I am bidding a sunroom to be built on an existing 12′ X 27′ concrete patio. The slab is 4″ mono with 12″ edges supported by 8″ blocks 7′ on center around the outside edge and is 3′ – 5′ above grad on the 27′ side. I don’t know what, if any steel is in it, but it is several years old and there are no cracks. It slopes away from the house and the owner wants the addition floor level.
Should I use tapered pressure treated sleepers with a plywood subfloor or could I pour a new level 4″ slab on top of the existing slab? The addition will be trussed along the 27′ span so the dead load will be on the outside walls. But I’m concerned about putting 4000 lbs. of new concrete on an old slab with no piers except around the outside edge.
Thanks for any suggestions or help.
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Good afternoon Murray,
Either methods are fine.
My concern is always with the structural integrity of the addition and more specifically what it rests on.
The owner may want to consider adding underpinning to the area that will support the majority of the load OR even a sono tube at the corners, set down below frost levels.
Whenever you bid a job like this, it's always wise to note in writing, to the owner, that you are not responsible for the existing slab that you are going to build onto.
Take care,
Gabe
*Murry, the use of sleepers might give you an easy solution to the extension of HVAC and electrical services to the perimeter of the new room.Good luck, Steve
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I am bidding a sunroom to be built on an existing 12' X 27' concrete patio. The slab is 4" mono with 12" edges supported by 8" blocks 7' on center around the outside edge and is 3' - 5' above grad on the 27' side. I don't know what, if any steel is in it, but it is several years old and there are no cracks. It slopes away from the house and the owner wants the addition floor level.
Should I use tapered pressure treated sleepers with a plywood subfloor or could I pour a new level 4" slab on top of the existing slab? The addition will be trussed along the 27' span so the dead load will be on the outside walls. But I'm concerned about putting 4000 lbs. of new concrete on an old slab with no piers except around the outside edge.
Thanks for any suggestions or help.