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Foundation/Porch slab Joint

ts2021 | Posted in General Discussion on May 16, 2025 07:34pm

In Climate zone 5, eastern. Got some delamination, chipping going on for both sides of the porch slab, foundation joint. We had one of the coldest freeze and thaw cycles in 2024, 2025. It doesn’t seem to be getting any worse, but it looks ugly.

In the fall of 2024, I wire brushed it. I then got thin aluminum stock and stuck it in the joint so I can mortar both sides. I used Portland and mason sand, and I also tried hydraulic cement. It’s just too thin in some areas. It just isn’t strong enough and falls out but I thought it wouldn’t hurt to try it. When it rains or snows the porch gets soaked on this side, so that isn’t helping either as the wind blows the rain into this side of house.

What can be done about this? Epoxy injection? urethane sealant?

I was also thinking about grinding a very slight chamfer on the chips to feather it out. I also thought about widening the horizontal joint by cutting a nice clean 1/8”-3/16” slot in that transition joint and filling it with sealant. 

My last question is should I sandblast the drylok off ?  There is drylok paint on foundation above grade only. Basement interior is not painted.

Thank you

Reply

Replies

  1. User avater
    ct_yankee | May 17, 2025 07:21pm | #1

    Is there interior basement space below the porch slab?
    This is obviously a construction joint between the foundation wall and the porch slab pour. Another example of less than professional residential concrete construction.
    What is your goal - aesthetics or durability?
    The Drylok paint is likely pure aesthetics - I would do anything with that until you resolve your concerns about the joint.

    1. ts2021 | May 18, 2025 03:07am | #2

      Look at the blueprint attached. Look at the dimension 21'-2". That's where the full basement is. The problem area is "Unexcavated Area" There is nothing but stone and backfill under the porch slab.The cracking area is circled. That's what I'm trying to solve. How to go about it. I can worry about Aesthetics when this is solved.

  2. User avater
    ct_yankee | May 18, 2025 12:45pm | #3

    The concrete above the crack is the slab concrete, and below is the wall placement concrete. The very top of the wall placement is usually crappy concrete if care was not exercised as it was finished (i.e. there was no proper finishing).
    Best course of action: Rout out the crack widening it to at least 1/2" or more taking most of it off the wall portion. Find a good repair mortar, follow the manufacturer's instructions to the letter, fill the routed out groove, cure the repair mortar properly and you should be good. Be sure to dampening the concrete before applying any mortar. Concrete should be DAMP, not dripping with water.

  3. ts2021 | May 18, 2025 06:14pm | #4

    Yes, I had that thought in mind but wasn't sure if that would be a good approach. Clean it out with a 7 inch grinder and masonry blade. I was also thinking about a good masonry epoxy or caulking, however i like your idea better because of the strength. A good mix that i can pack it in, not to wet.

    Otherwise, yes I've learned quite a bit and I've seen quite a bit of shoddy workmanship. Live and learn. Honestly, I can do better with a little heart, patience and perseverance. It's sad what's going on.

    Thank you for your help and support. I greatly appreciate it.

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