Velux flat roof window in warm, flat, grp roof

[foundationer]

Hi,

Quick question re. installing one of these. It's going to be a 100x150 one so pretty hefty!

Is there any need to get the warm roof kerb extension velux sell? Seems like it'd be easier just to put 120x45 timber around where the window's going to be fitted, stick the roof insulation round that & the deck over it (120mm insulation). Am I missing something important?

Also GRP + Velux plastic kerb. Is that going to be tricky or does it bond fine?

Thanks!

 

[freddiemercurystwin]

Yes the velux will leak when installed in a flat roof, it's designed to be installed in a pitched roof, that's why they make the kerb.

 

[foundationer]

Ah. But i'll be getting the flat roof velux. Which also has some kind of kerb available but just to cover the depth of the insulation.

 

[noseall]

I think what the OP is saying is that there are two types of Velux flat roof kerb, correct?

One to deal with a regular flat roof and the other to deal with a warm deck flat roof i.e. the added thickness of insulation, yes/no?

If it were me, I would always opt for the Velux solution rather than cobble something up myself.

 

[foundationer]

That's right noseall. Just seemed to me as though in this case they've made a pricey product to fix a problem that doesn't really exist. Fair enough re. the kerb that puts your roof window at 15 degrees in a flat roof - that's at least slightly complicated. But a kerb to simply bring the flat roof window up to the height of the insulation in the warm deck?