extend stoop and cover with flagstone

by Tom
(Bethesda, MD)


I have a 5' x 4' x 4" concrete stoop entrance the is 5" below the threshold and 4" off the ground. I think it might look better extended 2' either side and topped with square or rectangular flagstone. Concrete is clean but 17 years old. There is a 5' wide concrete path set with 24" rectangular slate already, and 2'wide concrete sidewalks going into the front of the sloop.

I'm worried that there will be cracks due to movement of old vs new concrete that will be transmitted up thru the mortar to the stones.

To do what I want, I wonder if this is correct:
1) excavate soil 5", cut out 2" more on the edge;
2) put in wood forms for concrete;
3) drill in 3 12" x 5/8" holes into each side of the existing stoop to put in 2' x 1/2" rebar and epoxy it in;
4) pour in concrete mixed from 4 bags of 80 lb concrete, smooth to level with existing stoop, on each side;
5) keep covered and moist - wait a day or 2 to cure;
6) etch old concrete with acid wash for concrete;
7) put on a 1/4" layer of modified thinset mortar;
8) put on a 1" of stone setting mortar;
9) butter bottom of stones with some thinset with laticrete admix added;
10) put in stones making them level on top with 1/2" spacing;
11) wait a day or so, then grout with a grout bag filled with thinset with laticrete admix added, use tuck pointer to put in a U channel in grout line.
12) remove wood forms;
13) wait a day or so, put in a sealer over everything.

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you're an expert
by: David

Dear Tom,

You sound like somebody who knows what they're doing. Your plan seems great.

You could get some cracks between the old and new, but the cracks will come in the joints. That usually doesn't happen for years and you can always easily replace the joints if that happens.

Great luck with your project!


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