Need culvert/catch basin help. 24" culvert into 28" hole (see picture)

I agree. Cut a piece of card board roughly the arch of the pipe to hold on the backside to help with waste. Foam will expand and act as a filler.

Temporarily seal off the outside of the basin at the pipe with gorilla tape and back that with plywood and dirt for reinforcement.

From the inside of the basin fill the gap with closed cell spray foam. wear gloves


Once dry remove the tape and plywood and use fiberglass mortar tape and quick patch to create a durable outer seal around the pipe and then back fill the hole with dirt once dry.

You could also put same tape and mortar on inside if you wish.








As the culvert and basin settle though it is very like that the mortar will crack.

Back it with cardboard or foam and fill gap from the inside with grout. Will need to pump the water out before you do the work.

Stuff the larger gaps with concrete brick or some sort of solid material, that way you use less grout, and then fill in the voids with non shrink grout. That's how the parish would do it

A piece of plywood, cut to overlap the basin and cut a hole for the culvert to fit. Cut in half and place it to the inside. Use a couple small pieces to join them together. Do the same for the outside, but before installing the top half, mix some concrete (bag of 80lb), pour in the bottom half. The to top, cut a small opening to were you can pour more concrete and join that to the bottom half. Fill the rest up with concrete. Back fill with dirt and it's done. The plywood will rot out over time.