Re part L robust details requirement to fit windows with the frame
30mm back into the cavity / insulated cavity closer.

I'm fitting windows now (just done one) and to pre-2006 regs as it
happens. Frames are 70mm. To set back 30mm as is required for
post-2006 part L, leaves only 40mm against the outer leaf. Considering
the design of the PVCu profile and the desire for weatherproofing and
getting a firm fix, this is impractical. To drill very close to the
front of the profile does not really work, and drilling too near the
edge of the brick risks blowing the brick either when drilling or when
the frame fixings are tightened. In the end I set back the frame by
about 15mm.

Anyone fitted windows to these regs, and how did you do it to get a
secure fixing in the brick ?

Simon.

sm_jamieson
wibbled on Saturday 16 January 2010 22:01

Re part L robust details requirement to fit windows with the frame
30mm back into the cavity / insulated cavity closer.

I'm fitting windows now (just done one) and to pre-2006 regs as it
happens. Frames are 70mm. To set back 30mm as is required for
post-2006 part L, leaves only 40mm against the outer leaf. Considering
the design of the PVCu profile and the desire for weatherproofing and
getting a firm fix, this is impractical. To drill very close to the
front of the profile does not really work, and drilling too near the
edge of the brick risks blowing the brick either when drilling or when
the frame fixings are tightened. In the end I set back the frame by
about 15mm.

Anyone fitted windows to these regs, and how did you do it to get a
secure fixing in the brick ?

Simon.

Easy. I ignored the regs. Or to be precise, I didn't bother reading them in
the first place. Having got Part L compliant windows, egress (my
requirement) and trickle vents (well, they were more or less there by
default) I just went with common sense on the rest.

I placed my windows such that I got it most of the way over the cavity, but
I gave far more priority to getting a good fixing in the outer leaf of the
bricks.

I showed one to the BCO and he was happy.

Personally, if it's a choice between a decent fixing or a minute bit of
thermal leakage, no one but God himself is going to tell me the fixing takes
lower priority.

Do what is sensible, try to cover the cavity as far as is practical. It
would be a mean spirited BCO who would argue about such a trivial thing. If
necessary, be prepared to argue that any other method of placement was
simply impractical.

If you are really paranoid or your BCO is an absolute nazi, call him up
first and tell him what you are proposing and why. I'd be surprised if he
cared, as long as you've considered the options.

There is one other option - which is to drill the frames at a slight angle
to give your fixings advantage. Also, if you use Fischer frame fixings,
there will be relatively low expansion forces (I only use Fischer so I can't
answer for others) - I think my fixings went in about 20mm (didn't actually
measure them) from the edge of the bricks without issue, though my frames
did permit drilling quite far forward.

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

On 16 Jan, 22:21, Tim W wrote:
sm_jamieson
* wibbled on Saturday 16 January 2010 22:01



Re part L robust details requirement to fit windows with the frame
30mm back into the cavity / insulated cavity closer.

I'm fitting windows now (just done one) and to pre-2006 regs as it
happens. Frames are 70mm. To set back 30mm as is required for
post-2006 part L, leaves only 40mm against the outer leaf. Considering
the design of the PVCu profile and the desire for weatherproofing and
getting a firm fix, this is impractical. To drill very close to the
front of the profile does not really work, and drilling too near the
edge of the brick risks blowing the brick either when drilling or when
the frame fixings are tightened. In the end I set back the frame by
about 15mm.

Anyone fitted windows to these regs, and how did you do it to get a
secure fixing in the brick ?

Simon.

Easy. I ignored the regs. Or to be precise, I didn't bother reading them in
the first place. Having got Part L compliant windows, egress (my
requirement) and trickle vents (well, they were more or less there by
default) I just went with common sense on the rest.

I placed my windows such that I got it most of the way over the cavity, but
I gave far more priority to getting a good fixing in the outer leaf of the
bricks.

Most of the way over the cavity ? How ? What size was the cavity ?


I showed one to the BCO and he was happy.

Personally, if it's a choice between a decent fixing or a minute bit of
thermal leakage, no one but God himself is going to tell me the fixing takes
lower priority.

Do what is sensible, try to cover the cavity as far as is practical. It
would be a mean spirited BCO who would argue about such a trivial thing. If
necessary, be prepared to argue that any other method of placement was
simply impractical.

Well I'm only 15mm into an 75mm cavity. The frame had some ridges near
the front that would not have made for a very easy fixing so I fixed
about 30mm from the front.
If they fuss I will add some more insulation under the plasterboard on
the reveal.

If you are really paranoid or your BCO is an absolute nazi, call him up
first and tell him what you are proposing and why. I'd be surprised if he
cared, as long as you've considered the options.

There is one other option - which is to drill the frames at a slight angle
to give your fixings advantage. Also, if you use Fischer frame fixings,
there will be relatively low expansion forces (I only use Fischer so I can't
answer for others) - I think my fixings went in about 20mm (didn't actually
measure them) from the edge of the bricks without issue, though my frames
did permit drilling quite far forward.

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

sm_jamieson
wibbled on Saturday 16 January 2010 22:31


I placed my windows such that I got it most of the way over the cavity,
but I gave far more priority to getting a good fixing in the outer leaf
of the bricks.

Most of the way over the cavity ? How ? What size was the cavity ?

Sorry - I have to confess to talking ********. I forgot one key thing which
was the cavity was closed with brick (1950's house). There was a 3/4" gap
where the DPC was inserted and I was concerned to cover that with the window
frame.

Been too busy looking at a new doorway I had cut into the wall, and that of
course is cavity closed the modern way.

Sorry - brain spas moment. But as the closure was done by bricks from the
inner leaf towards the outer, I faced a similar dilemma to the OP in the I
could either fix to the closure bricks or to the outer leaf.

Due to frame design and needing the frame to seal against the outer leaf, I
had to bring the window outwards such that the fixings were good.

The only differece for the OP is (presumably) heel need to stuff some cavity
closer in first.


Well I'm only 15mm into an 75mm cavity. The frame had some ridges near
the front that would not have made for a very easy fixing so I fixed
about 30mm from the front.
If they fuss I will add some more insulation under the plasterboard on
the reveal.

I don;t think there will be a problem for the OP, if he is using cavity
closers - those have a bock of insulation anyway inserted into the cavity.

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

[Default] On Sat, 16 Jan 2010 14:01:58 -0800 (PST), a certain
chimpanzee, sm_jamieson , randomly hit the
keyboard and wrote:

Re part L robust details requirement to fit windows with the frame
30mm back into the cavity / insulated cavity closer.

This requirement has been in place for at least 15 years to my
recollection, but is stoutly ignored by all and sundry.

The requirement is there to prevent cold bridging. Insulated
plasterboard to the reveal should suffice.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have I strayed"?

On 19 Jan, 21:20, Hugo Nebula abuse@localhost wrote:
[Default] On Sat, 16 Jan 2010 14:01:58 -0800 (PST), a certain
chimpanzee, sm_jamieson , randomly hit the

keyboard and wrote:
Re part L robust details requirement to fit windows with the frame
30mm back into the cavity / insulated cavity closer.

This requirement has been in place for at least 15 years to my
recollection, but is stoutly ignored by all and sundry.


Not surprised, since it is impractical. I was also fitting a french
door which needs a solid fix on the bottom of the frame which may be
stood on. And I wanted the door and window recess to match.

The requirement is there to prevent cold bridging. Insulated
plasterboard to the reveal should suffice.
--
That was the conclusion I had come to !
I'll also have a thick piece of celotex under the interior window
board to hide the back of the exterior window sill, which should take
care of that !
Cheers,
Simon.