Clarification on resistance to moisture (C2).

[GaryinAshby]

A neighbour asked me to help him out with planning & b.regs application, as he knew I had done my own plans around 4 years ago. The application os for a full-plans b.regs approval as he intends to do a lot of the work himself, using contractors as & where necessary.

The extension is a single storey side extension (bathroom) on the side of a bungalow. The plans came back as rejected for one reason:

C2 Resistance to moisture. Please detail how 3 coats of RIW are to provide an adequate DPM which is to be lapped with the DPC within the external walls.

Can someone clarify exactly what the BCO is asking here? The only mention of "3 coats" in the plans are three layers of felt for the roof.

Any advice appreciated.

Thankyou.

 

[garyo]

Is he asking how you propose to make a moisture seal between the DPM on the new floor, and the DPC in the existing external wall?

Gary

 

[GaryinAshby]

I think so, what I wrote was all that was listed in the schedule of defects & omissions. I tried to contact the BCO but he's on holiday for two weeks.

When I built my own extension, the new floor DPC was simply chased into the mortar course of the existing wall (ie. chopped out the mortar course in the outer walls DPC & lapped the new floor DPM into this & repointed). This was okay with the BCO at the time.

The bit that threw me out was "3 coats RIW" as that isn't mentioned anywhere in the plans and he uses the sentance as though he's plucked it out of the plans?

 

[GaryinAshby]

Just a thought..... As this is a bungalow & the flat roof felting runs under the roof tiles of the bungalow, is he reffering to that, rather than the floor DPC? That would make more sense as I have quoted three layers of roofing felt?

 

[hotrod]

Are you not using a traditional Visqueen type DPM for a new floor? Is it an exiting floor? Sounds like the BCO thinks you're applying a retro DPM to an existing floor maybe, http://www.riw.co.uk/applications/dpm.htm ?

 

[GaryinAshby]

The way that my own extension was done was DPM, cellotex, barrier, concrete slab, tiles. The DPM was left over length at the point where we broke through the outer/inner walls to the house and the existing house floor slab was cut back by 6", exposing the original DPM under the house floor slab. The new DPM for the extension was then overlapped over the original house DPM by 6" & the slab made good. This satisfied my BCO a couple of years ago.

Nowhere on my neighbours plans have I stated RIW hence the reason for my confusion.

 

[DevilDamo]

If RIW (which is primarily used as a waterproofing membrane) is not stated on the plans, then ask the BCO what he/she is referring to.