Insulation detail above cavity tray

11 Apr 2006
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United Kingdom
I'm installing cavity trays above two Catnic lintels. I'm using 450mm wide DPC to form the trays.

The cavity insulation is full fill rockwool. Should I install the insulation above the tray as normal and butt it right up against the tray? Should I cut a diagonal end on the insulation bat so that it's snug and minimises and air gaps?


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You can angle of the long edge of bat if you want, although we never bother. Just so long as bat is below top of lintel, then your lintel insulation will cover your U value. Regards air pressure loss, you have to have a real scab of a bricklayer not to be able to comply with 10m3/(h.m2)@50Pa. Not that you have to comply.
Regards oldun
Gary, Forgot to mention that Catnic now state that with open back lintels a dpc tray is only required for extreme exposures. No matter what they say, we still fit them no matter what the exposure.
We have recently had an architects drawing back stating "full fill dritherm - no cavity trays required".

I am well aware of dritherms' waterproof capabilities as i have seen this stuff floating in water without letting any water through, but it is the first time i have noted reference to the use of dritherm negating the need for CT's.
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Cheers guys. I'll continue to 'go through the motions' and fit the trays, but the more I read the less I'm sure it matters :)


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