I've just been on the phone to Building Control (BC) asking if UPVC
door and window frames need cavity closures, using either:

the propriatary strips (e.g
http://www.screwfix.com/app/sfd/sea/...pi=1&cn=1&cd=1)

or a run of dpc up the edge of the outer leaf of the cavity wall and
then folded back into the cavity.

I was told that it is best to do this as there is a small chance of
leakage to the inside edge of the frame which could then pass onto the
material used to cover the reveal (e.g. plasterboard)

Another point BC made was how was the plasterboard to be supported on
the outer leaf. If a small lip was left (i.e. the frame was not flush
with the inner edge of the outer leaf) to fix the p/b to, this is then
a cold bridge and there is then the risk of black mold growing up the
inside edge of the frame.

Questions.
I would like to use dpc and not cavity closures if possible, so is
there a method of supporting the plasterboard in the reveal?

Is the risk of black mold growth high?

Thank you

nafuk wrote:
I've just been on the phone to Building Control (BC) asking if UPVC
door and window frames need cavity closures, using either:

the propriatary strips (e.g
http://www.screwfix.com/app/sfd/sea/...pi=1&cn=1&cd=1)

or a run of dpc up the edge of the outer leaf of the cavity wall and
then folded back into the cavity.

I was told that it is best to do this as there is a small chance of
leakage to the inside edge of the frame which could then pass onto the
material used to cover the reveal (e.g. plasterboard)

Another point BC made was how was the plasterboard to be supported on
the outer leaf. If a small lip was left (i.e. the frame was not flush
with the inner edge of the outer leaf) to fix the p/b to, this is then
a cold bridge and there is then the risk of black mold growing up the
inside edge of the frame.

Questions.
I would like to use dpc and not cavity closures if possible, so is
there a method of supporting the plasterboard in the reveal?

Is the risk of black mold growth high?

Thank you

The frame should cover the DPC and not be flush with it. This stops any
moisture bridge.

I don't don't know what the BCO was thinking when he mentioned
supporting the plasterboard on the outer leaf? The plaster goes up to
the frame only and does not touch the outer leaf - it is fixed to the
inner leaf and reveal only.

If using aerated blocks, then you can return these at the reveal and
use nomal DPC. If the blocks are concrete, then you should use an
unsulated DPC or one of the propriatary closers.

dg

Thank you for your reply.

My problem is that I have a cavity wall (brick outer, aerated block
innner) with no blocks turned into the cavity and so can only stick the
p/b to the inner leaf. How can I offer more support?

Thank you


dg wrote:
nafuk wrote:
I've just been on the phone to Building Control (BC) asking if UPVC
door and window frames need cavity closures, using either:

the propriatary strips (e.g
http://www.screwfix.com/app/sfd/sea/...pi=1&cn=1&cd=1)

or a run of dpc up the edge of the outer leaf of the cavity wall and
then folded back into the cavity.

I was told that it is best to do this as there is a small chance of
leakage to the inside edge of the frame which could then pass onto the
material used to cover the reveal (e.g. plasterboard)

Another point BC made was how was the plasterboard to be supported on
the outer leaf. If a small lip was left (i.e. the frame was not flush
with the inner edge of the outer leaf) to fix the p/b to, this is then
a cold bridge and there is then the risk of black mold growing up the
inside edge of the frame.

Questions.
I would like to use dpc and not cavity closures if possible, so is
there a method of supporting the plasterboard in the reveal?

Is the risk of black mold growth high?

Thank you

The frame should cover the DPC and not be flush with it. This stops any
moisture bridge.

I don't don't know what the BCO was thinking when he mentioned
supporting the plasterboard on the outer leaf? The plaster goes up to
the frame only and does not touch the outer leaf - it is fixed to the
inner leaf and reveal only.

If using aerated blocks, then you can return these at the reveal and
use nomal DPC. If the blocks are concrete, then you should use an
unsulated DPC or one of the propriatary closers.

dg

nafuk wrote:
Thank you for your reply.

My problem is that I have a cavity wall (brick outer, aerated block
innner) with no blocks turned into the cavity and so can only stick the
p/b to the inner leaf. How can I offer more support?

Thank you



More support to what?

The two leafs should have ties every block course at the reveal so they
support each other, and if you have not returned the blocks, then you
will have to use a propriatary cavity closer.

Plasterboard is just dabed or fixed to battens on the blockwork and can
be fixed to eht end of the blocks in the reveal up to the frame

dg

dg wrote:
nafuk wrote:
Thank you for your reply.

My problem is that I have a cavity wall (brick outer, aerated block
innner) with no blocks turned into the cavity and so can only stick the
p/b to the inner leaf. How can I offer more support?

Thank you



More support to what?

The two leafs should have ties every block course at the reveal so they
support each other, and if you have not returned the blocks, then you
will have to use a propriatary cavity closer.

Plasterboard is just dabed or fixed to battens on the blockwork and can
be fixed to eht end of the blocks in the reveal up to the frame

dg

I have not returned the blocks since a BCO and a builder told me
because of cold bridging this was no longer acceptable.

Door fitters say that the cavity closures make the door fixing less
stable because of the strip of membrane/plastic running down the outer
leaf reveal. Does anyone know if this is just like a strip of plastic
DPC?

The inner leaf is thermalite expanded blocks and are very easy to saw,
so I could cut some returns in that don't touch the outer leaf. This
would offer additional support to the p/b in the reveal.
Is this a good idea of is there something easier and quicker I could
use (like drilling some screws in etc.)?

Thank you