Decks, Patios, Porches and Docks - How to avoiding patio slab Undermining?
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wreken
05-12-08, 07:32 AM
Please help, the question is:
How do I core through and an existing concrete patio slab, excavate for several round concrete piers to support a pergola and avoid undermining the slab, thus causing inevitable cracks/settlement of the patio slab within years of this work?
The pergola is big 20 x 20 and the weight of all the wood I believe mandates piers.
Please help, our patio is beautiful as it is, Just too too sunny!
Chicago area- depth needed approx 36" below grade.
How do I core through and an existing concrete patio slab, excavate for several round concrete piers to support a pergola and avoid undermining the slab, thus causing inevitable cracks/settlement of the patio slab within years of this work?
The pergola is big 20 x 20 and the weight of all the wood I believe mandates piers.
Please help, our patio is beautiful as it is, Just too too sunny!
Chicago area- depth needed approx 36" below grade.
lefty
05-12-08, 06:02 PM
So, other than 36" deep, how big do your footings have to be?
In the past 15 years I have installed at least 400 to 500 patio covers where I've had to cut an existing slab in order to dig the footings. I've NEVER had a problem with the slab becoming undermined.
Cut the slab to the width of the footing, bust and remove the concrete inside that rectangle, dig the hole to the needed depth, get it inspected, then fill it with concrete.
Since you are doing a wood pergola, set your standoff post or column bases in the wet concrete. Let it cure a couple of days, then start building.
In the past 15 years I have installed at least 400 to 500 patio covers where I've had to cut an existing slab in order to dig the footings. I've NEVER had a problem with the slab becoming undermined.
Cut the slab to the width of the footing, bust and remove the concrete inside that rectangle, dig the hole to the needed depth, get it inspected, then fill it with concrete.
Since you are doing a wood pergola, set your standoff post or column bases in the wet concrete. Let it cure a couple of days, then start building.