I had a leaking problem at the clamping flange/drain assembly in a shower
drain. I decided to cut out the slab around the drain head. Approximately
12" x 12" box down to the dirt, exposing the drain head and trap. I scored
and snapped off the original drain head, about 40 years old! I want to
replace the drain assembly , cement in and then put in a shower pan.
Problem I am running into is how to fill it so it is structurally solid. I
decided on a product called CementAll. It is a fast curing cement. The
dirt under the slab has settled over the years and so I had to build up the
area under the hole with dirt and put a layer of silver sand on top. On a
couple of the corners the sand just slips through. It was a tight area and
I decided not to build a form as it would have been difficult with pipes in
the way, etc. I drilled 1/8" pilot holes and hammered in masonary nails to
act as keys and will fill with cement. Is there anything that will help the
cement to adhere better to the sides of the opening and prevent it from
slipping through?