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irmedic 08-19-2008 03:32 PM

Concrete porch problems
My room mate and I are having problems with our front porch sinking. We placed stones under the part that was sinking about a year ago and a couple of days ago we used an expandable foam for a quick fix, but now we want to fix the problem the right way. We have used a jackhammer to break the concrete up and now we are trying to figure out how to set the new concrete slab correctly. Does anyone know have to do this? Any information would be great. Thank you.

glennjanie 08-19-2008 04:50 PM

Welcome IRMedic:
Porches so often become a waste dump for the contractors working in the house. This waste has a tendency to settle and decompose, leaving the floor to settele.
After you have removed the concrete, make sure there are no materials in the fill that will decompose and settle over the years. The fill should be thorughly compacted dirt up to 4" below the concrete. The last 4" of fill should be crushed limestone (#6 stone, DGA, or #54 stone).
If the porch is abutting a brick wall you need to break out a brick every 4' and place a 16" #4 reinforcing bar in the hole, extending out into the concrete. Allow the concrete to fill the hole for a key way to hold the back edge of the floor. Place heavy building paper over the holes in the concrete block foundation to hold the concrete from filling all the blocks. Use 6x6 10/10 reinforcing wire at mid point height in the concrete.
We would appreciate pictures before and after to see how it turned out.

irmedic 08-19-2008 07:33 PM

Concrete porch problem part 2
Thank you so much for the reply. After we jackhammered out the porch we now have found that there is a gap in between the slab of the house and concrete blocks (about 1 to 1.5"). We are not sure what to make of this... is this an expansion joint? or do we have a bigger problem to deal with now? We had a problem with water collecting around the front porch for a long time because of street and driveway runoff when it rained. We corrected this runoff (water) problem. Below I have attached a picture just in case I confused you. Any information would be helpfull. Thank you.

glennjanie 08-20-2008 01:26 PM

Hello IRMedic:
The picture didn't show up; perhaps you could try again.
A residence would not have a 1 to 1-1/2" expansion joint; you may have a bigger problem.
It is good that you corrected the runoff problem; that should eliminate future problems.
If we are talking about a space between the house proper and the concrete blocks supporting the porch, then you have a porch foundation that is settling away from the house. If the house is over 10 years old the settling should be over by now, you could simply use mortar mix to fill the big joint and give you some continuity. You may want to put some rolled up paper in the joint so that you only have to fill 1" deep with the mortar. A Sackrete or Quickrete mortar mix would be sufficient, just add water but keep it very stiff (just dampen the mix so that it will make a ball in your hand but fall apart when you drop it). You will need a sponge trowell to press the mortar in and sprinkle it and re-sponge it at 15 minute intervals for 4 or 5 times. This will keep the mortar from shrinking away from the blocks or the house and leaving a crack.

Charlie 08-20-2008 01:36 PM


Originally Posted by glennjanie (Post 21740)
Porches so often become a waste dump for the contractors working in the house. This waste has a tendency to settle and decompose, leaving the floor to settele.

That is a really good point and something that I hadn't ever really though about, but have been guilty of doing myself on occasion. I will have to be more careful in the future.

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