Casting a constructional hearth - DPM or not.

[marklamond]

Hi folks,

Just a quick question about casting a constructional hearth on front of the existing cast shown in the picture.

On top of a compacted base should i put down a DPM below and up the back of the new cast to isolate it. The existing cast will be damp as it is in contact with earth & original stonework.

Or pour the new cast on a compacted base without DPM, but isolate any woodwork touching new cast with DPM.

First option seems the most sensible?

Slab will be 200-250mm deep.

Many thanks once again,

 

[hotrod]

I would use a DPM. This will:-

1. Isolate the hearth from any ground moisture
2. Protect any existing timber from your newly poured hearth whilst it cures.

It's pennies and well worth doing.