Quick question, building a log cabin at present. The roof is 19mm tongue and groove, Kingspan Tr27 and 6mm external ply. I have bitumen roofing shingles, but would like to understand if I should put some roofing underlay on before laying the shingles? Thanks for the help.
Do I need underlay before laying roof shingles?
- Thread starter ac505
- Start date
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how about something like a breathable membrane: http://www.screwfix.com/p/protect-a1-roofing-underlay-1m-x-45m/31795
or
http://www.screwfix.com/p/rica-medium-grade-roofing-membrane-each/39544
or
http://www.screwfix.com/p/rica-medium-grade-roofing-membrane-each/39544
R
RedHerring2
I think it's pointless using a breathable membrane 'cos it wouldn't be able to breathe.
I think breathable membrane needs to have a gap either side of it for effectiveness.
I used felt type shingles on my workshop a few years ago now, and the type of undelay and method was printed on the wrapper of the shingles.
I think breathable membrane needs to have a gap either side of it for effectiveness.
I used felt type shingles on my workshop a few years ago now, and the type of undelay and method was printed on the wrapper of the shingles.
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Aye I'd think a good felt underlay would be best.
If you're in Scotland you'd use sarking boards, none of this mucking about with felt.
What and no felt?
could this be sarking
I daresay it could be
You shouldn't really need felt under the shingles but put it if the mfr's instructions say to or you think the roof will be vulnerable to driven rain.
You shouldn't really need felt under the shingles but put it if the mfr's instructions say to or you think the roof will be vulnerable to driven rain.
R
RedHerring2
You have to wonder why some people ask for advice!
If you read the instructions for your Marley Roof Underlay you'll see that it should have counter battens fixed above it when it's used in a "fully supported" installation, ie. on sarking boards.
This is to provide an air space above the underlay so it can breathe.
You can't fix felt type shingles to counterbattens. Therefore, there is a risk that your undelay could rot due to no or little airflow, or even continuous damp.
If you read the instructions for your Marley Roof Underlay you'll see that it should have counter battens fixed above it when it's used in a "fully supported" installation, ie. on sarking boards.
This is to provide an air space above the underlay so it can breathe.
You can't fix felt type shingles to counterbattens. Therefore, there is a risk that your undelay could rot due to no or little airflow, or even continuous damp.
Looked at a roof last week with shingles that is leaking now. It was done about 20 yrs ago and they are just nailed to the t & g no underlay some have now blown of and are brittle the pitch at a guess 30 degree's. not sure about the use of underlay if you are going to put a million holes in it.
R
RedHerring2
IIRC, shingles have an expected life of 25 years, with an underlay.
You could put another layer straight on top of the first layer.
You could put another layer straight on top of the first layer.
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