Filling hole/repair in 1960s subfloor

[diyfloorhelp]

Hi, looking for and advice as to how to proceed. Read the guides but the hole might be too deep at max 60mm.

Removed a kitchen and the subfloor wasn't level under old sink. There's a rectangular hole roughly 1100mm x 500mm x up to 60mm. Original DPM has deteriorated, brick is visible on outside wall.

Im unsure of order of operations and where to place a new dpm. The hole is too deep for normal self leveling and maybe too shallow for standard concrete. Plan was liquid dpm with a sand mix, prime, deep fill self level, prime, smoothing compound. But unsure about outside wall and bitumen.

Advice appreciated.

 

[Wayners]

Vacuum off.
SBR and cement mix and brush on to seal and bind surface.
Give that half hour to dry off a bit.
If its fairly smooth place DPM plastic over.
5-1 Sharp sand and cement.
As it sets after 3 hours or more wet surface and polish off.

After sealing with SBR and cement you may see sharp bits that could puncher DPM so you need to smooth over with a bit of sharp sand and cement prior to placing DPM over. This is why I think it's a good idea to seal.
You don't have to seal as you are placing plastic over...
I've just used PVA in the past to seal...

You can easily get a depth of 50mm with sharp sand and cement. If it's deeper do in two goes

 

[diyfloorhelp]

Thanks for the reply.

I think some of the sharper bits may puncture a plastic dpm, so I'd be happy to seal with sbr and raise it up with cement. I'd just read that under 50mm depth of cement wasn't recommended.

Should I leave a gap around the edges or go right up to the bricks. Cheers

 

[Wayners]

Mix a 2 handfuls of cement with 1lt of SBR to make a slurry mix. Same used on slabs to seal the back.
Good sealer and bonding mix.
Sharp sand and cement 5-1 although sometimes I mix 4-1 whatever.... Not really any noticeable difference when set..
You can build up 50mm.
If you want more depth give it a good hour to set a bit and hit it again with another mix on top..

 

[diyfloorhelp]

Excellent. Thanks for the advice