First, the Catnic lintel I'll be using (L-section)[1]) has a note saying 
a DPC should be used; checking the info on the mfr's website
<http://www.catnic.com/Downloads/pdf/How to Install a Cavity Wall 
Lintel.zip> it just says:

"Install a separate DPC in severe exposure conditions. A Catnic Cougar 
Open Back or Classic Combined Box Lintel with an additional DPC membrane 
installed in accordance with normal practice provides the best
possible protection."

Where is this DPC supposed to go?  Under the steel and above the 
supporting brickwork piers/windowframe? Or above the steel and below the 
brickwork which it supports?  And what happens at the two ends?!

Secondly (and thinking ahead a bit); once you've fitted a lintel in a 
cavity wall [2], knocked out the brickwork below, and installed the new 
uPVC window in the outer leaf - how do you block off the cavity (ie 
sides and top) to form the window reveal?

Is it just a matter of gluing bits of plasterboard over the gaps?

Thanks
David


[1] for a replacment window; lintel is for the external leaf only as 
there's already a lintel on the inner leaf.

[2] for a different window being fitted from scratch, with a cavity-wall 
lintel supporting both inner and outer leaves

"Lobster"  wrote in message
news:Ie_Ue.15405$vC4.74@newsfe4-win.ntli.net


> "Install a separate DPC in severe exposure conditions. A Catnic Cougar 
> Open Back or Classic Combined Box Lintel with an additional DPC membrane 
> installed in accordance with normal practice provides the best
> possible protection."

> Where is this DPC supposed to go? 


The only catnics I know of are a box section with a stepped top so that
the outer leaf of the wall sits lower down on it than the inner leaf. A
strip of wide DPC sits on this.

In other words, the cavity above the section is crossed with the dpc so
any water poured down on it from above falls down and out.

How you go about inserting it in your case is a different matter.


-- 
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In an earlier contribution to this discussion,
Lobster   wrote:


>
> Secondly (and thinking ahead a bit); once you've fitted a lintel in a
> cavity wall [2], knocked out the brickwork below, and installed the
> new uPVC window in the outer leaf - how do you block off the cavity
> (ie sides and top) to form the window reveal?
>
> Is it just a matter of gluing bits of plasterboard over the gaps?
>

The traditional method is to brick up the gap, but with a vertical strip of
DPC material immediately behind the outer leaf, to prevent a damp
transmission path.

Having said that, I've just had a new door and window inserted in the side
of my garage, and the builder glued plasterboard over the gaps!
-- 
Cheers,
Set Square
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"Lobster" wrote


> snip<
>
> Secondly (and thinking ahead a bit); once you've fitted a lintel in a
> cavity wall [2], knocked out the brickwork below, and installed the new
> uPVC window in the outer leaf - how do you block off the cavity (ie
> sides and top) to form the window reveal?
>
> Is it just a matter of gluing bits of plasterboard over the gaps?
>
> Thanks
> David


My builder has used plastic cavity closers

Regards Jeff