Keeping existing drains and applying a new layer of concrete

by Sophie
(Dublin, Ireland)

Q. I've got a large stretch of outdoor existing concrete in which trench drains are placed periodically about 6 metres apart. There are 6 of these drains. What I want to do is lay a new, relatively thin layer of concrete overlay on top of this to create a different finish. Can I keep the existing drains? Would building a wooden frame around them during the pouring of the new concrete, and then raising up the drain covering work?

A. The trench drain cover sits down inside the trench drain on a small ledger. If you recreate the exact profile of the trench drain with your new form then install it on top of the trench drain and pour the new concrete around it, the drain covers will sit down inside the new concrete overlay and be flush with the surface like they are now.

If the new concrete is a thin overlay like 3/8 of an inch, then just raising the drain covers would be easier.

Install a 2x4 block in place of the drain covers, it will need to be the exact width of the drain so the covers will sit back down inside. Pour around the block and pull it out the next day.

The drain covers will now sit back down inside. Use some pressure treated shims to make the covers flush with the new surface.