Sunken concrete slab – build on it or what?
I have an enclosed porch I’m looking to make conditioned space. One corner of the ground-level concrete slab has sunk about 2 1/2 inches. No cracks, the rest of the slab has moved along with it – so the whole thing is at a tilt.
The previous owner did not have gutters, which I’m thinking helped the slab sink funny (it’s an outside corner that is low). There has been no movement for the 15 years I’ve owned the house.
It’s enclosed now with a lightweight aluminum frame and panels (and windows/screens), and an aluminum roof. I’d like to put in 2x walls, insulate the existing roof, and an insulated floor (probably 2x sleepers).
My question is about that sunken corner and the out-of-level slab. If it was your house what would you do? I could make some guesses (pour a little knee wall, spacers, blast it up and put in a real footer, etc.), but would rather hear what the pros think. Also of note, where I live on Long Island the ground is really just sand pretty much as far down as you want to dig.
Thanks (and Merry Christmas)!
Replies
Rip It Out, Start Over
What you face is common to these 'stealth' remodels. The result in constant unhappiness and continual hacks to accomodate shortcomings.
A patio slab is NOT a foundation. It's not made as flat or as level as a slab foundation. It's not properly tied into the house foundation, so it doesn't 'move' with the house. It lacks footings that go below the frost line, so is heaves and floats all over the place.
Yet, folks cobble 'walls' around them all the time. They call them porches, sun rooms, whatever. They screen out the bugs. They slip in windows. Then, suddenly .... why, I can sell this house for more if I call it a bedroom! Yea, right.
Instead, do yourself a favor. Build a real room atop a real foundation - with the proper structural tie-ins to the house, the proper flashing, the proper electrical, the proper insulation, the proper HVAC.
What can go wrong? First off, there always seems to be a step up/ step down at the transition. Poor insulation and inadequate HVAC results in a room that's a lot less comfortable than the house itself. Leaks where it connects to the house are endemic- leading to moldy wall insides and rotted floors. The added weight makes slab movements worse.
Thanks for the reply. Rip it out and start over is good advice. I might do something half-assed but not so extensive as I had outlined (something that can be easily removed) just to make it more comfortable in the cold weather (until I can afforde better).