Sometimes you wish you'd read BH in more depth and more often....

[ToughButterCup]

What a way to start the week!

First thing this morning I re-read one of @JSHarris 's pearls of wisdom and realised that I should have read and remembered it a year ago because .....

 

 

Our roof has two 100mm  layers of PIR between the rafters. First layer of foam put in between the rafters - all tickety boo - installed before the first floor was fitted. Second layer put in over that stonkingly hot summer, and foamed - and forgotten about. Tiles put on - thank God for that.

 

Walk into the house, look up with relief to see the new roof keeping the rain out. 

 

Pause, look closer and swear gently.

 

The foam had pushed the bottom layer  downwards in half a dozen places. So, I've had to trim it back before underboarding with another 80mm of PIR. 

 

Low expansion foam. Who knew eh?

 

[Construction Channel]

I don't know how far you have gone but it may be easier to nail a batten along the rafters, depends how many need trimming though

[Pete]

1 hour ago, AnonymousBosch said:

What a way to start the week!

First thing this morning I re-read one of @JSHarris 's pearls of wisdom and realised that I should have read and remembered it a year ago because .....

 

 

Our roof has two 100mm  layers of PIR between the rafters. First layer of foam put in between the rafters - all tickety boo - installed before the first floor was fitted. Second layer put in over that stonkingly hot summer, and foamed - and forgotten about. Tiles put on - thank God for that.

 

Walk into the house, look up with relief to see the new roof keeping the rain out. 

 

Pause, look closer and swear gently.

 

The foam had pushed the bottom layer  downwards in half a dozen places. So, I've had to trim it back before underboarding with another 80mm of PIR. 

 

Low expansion foam. Who knew eh?

 

What have I told you about using foam!!

[vivienz]

Have you recovered from academia now, Ian?

[ToughButterCup]

6 hours ago, vivienz said:

Have you recovered from academia now, Ian?

 

Got it in one! 

[Cpd]

I have a dustbin full of short 200mmm wooden batten 50x25mm off cuts that I always use to hold the sheets in place as I go. These are screwed in about every 3- 400mm and are left on until the foam has fully sealed. Take them off, cut back the foam and re foam any gaps before taping. When I am over-sheeting the joists and foaming the back of the boards  I use full lengths of battens  to hold it all tight and space them out at about 3-400mm 

you can see the short stubby bits of wood holding the 50mm insulation that’s been inserted between the joists and the longer ones at the face of the joists holding in the 120mm insulation. I then put 25mm insulation sheets over the top using the long batten system. 

[ToughButterCup]

Thanks very much @Cpd. Very helpful.

[TerryE]

 AnonymousBosch vs HieronymusBosch. Is there some subtle inference here?  This one deserves an explanation! ??

Edited April 10, 2019 by TerryE

[HerbJ]

or do you just like Michael Connelly novels?

[ToughButterCup]

Jungs, ich bin doch 'n Deutscher. Bosch tool fanatic too. It fits dunnit?