I am working on an old house (built early 1920’s) the front porch is a 7’x42′ “L” shaped that has dropped approx. 2″ where the porch and house meet. the owner of the house has built piers under the house leveling and supporting it as required by local code and has set additional piers under the porch with the intention to pour over the existing slab. the thought is to pour over the existing porch with 4-5″ thickness where the porch has settled raising it to about 1 1/2″ below the door threshold and gradually taper down to approx 2″ at the exterior edge.
the piers put in place for the porch are to the inspectors specifications for the additional weight that will be put on the porch (approx 10000lbs.)
here are some of my questions for you guys:
1. should we even do this?
2. if we do go ahead with this idea, with the thickness mentioned would we still need to using epoxy (or some other kind of bonding agent)?
3. any pointers on how to screed against the house without there being a form against it?
4. any suggestions on how to finish the exposed edge that will show the two slabs?
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I did something similar. Here's a link to the thread on it. Maybe some of what I did will be of use to you.
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thanks for the link. it looks great...i am a pretty comfortable with what i do, but this one has me up late at nite doing a lot of reading, which i enjoy doing but not when im scrambling trying to figure out if i want to take this little project on or not.
1. should we even do this?
2. if we do go ahead with this idea, with the thickness mentioned would we still need to using epoxy (or some other kind of bonding agent)?
3. any pointers on how to screed against the house without there being a form against it?
4. any suggestions on how to finish the exposed edge that will show the two slabs?
1) Yes.
2) Sandblast surface and edge of existing, then paint the top with an concrete adhesive before the pour. Thouroughly wet the old slab the night before the pour.
3) Keep the new 'crete from contact with any organic material on the house with a tarred felt expansion material, (about 1/2" thick.) Tack a 2x4 right above the finish grade line to the house, add a 2x4, extending 1 1/4" to the top of your 2x4 screed on the house end. As soon as the mud sets up enough to finish, remove the 2x4 from the house.
4) Use a sponge float to put a fine, (100 mesh or smaller,) sand/cement "wash" over the old and new edges. A black sponge will give the smoothest surface, a red one will give a little more sandpapery finish.
5?) The biggest risk/problem you face is the 'crete drying out before it cures causing shrinkage cracks and edge curling. Lay a thick, (1/2" or more) layer of burlap on top and well over the sides and keep it damp for at least 72 hours, but best is 1 week. You can allow traffick over it the day after the pour.
SamT
A Pragmatic Classical Liberal, aka Libertarian.
I'm always right!
Except when I'm not.