roofing advice

[deuce22]

Hi.

Can someone explain or give me a link on the differences/reasons for the need to counter batten.

I'm building a Dormer Bungalow, which has vaulted ceilings and I want to calculate all the options that I have of insulating and fitting the roof.

Thanks.

 

[noseall]

here mebbe

 

[deuce22]

Cheers noseall.

I'll have a read through it.

 

[deuce22]

Hi.

I've read through it, but I'm still not 100% sure on the best way to go.

I have 150mm rafters and have been told by Celotex that I need to put 100mm of insulation between and 40mm underneath, I will also be using a breathable felt.

I Have had a few roofs done in the past with similar specs, but they have been covered differently.

One roofer felt and battened directly onto the rafters and then tiled and another roofer felted, then counter battened before battening for the roof tiles.

Both used vents in the soffit, but neither vented at the ridge.

What is the correct way?

Cheers.

 

[deuce22]

I am writing this just to let others know in case they come across the same problem.

I have spoken to both Celotex and Redland on the correct set up for the roof covering.

If the rafters are partially filled (so you have an air gap) then you use a breathable felt, but there is no need to counter batten. However if it is a complete fill then you need to create a breather gap, so you will have to counter batten the rafters before battening them out for the tiles.

If you are battening directly onto the rafters then you need to create sagging of the felt between each rafter for drainage. There is no need to do this if you are counter battening.

As this is a vaulted ceiling roof I need to create ventilation at the ridges and Redland told me that the whole length needs to be vented using a dry vent system.

The roofer I've been using always pulls the felt as tight as possible and then battens straight over the top. He also said that 2 or 3 ridge vents would be plenty. I don't know if Redland are going overboard, but I'd prefer to do that, than not do enough and it cause problems.

It doesn't give me much confidence in using him again.

Cheers.

 

[freddiemercurystwin]

I am writing this just to let others know in case they come across the same problem.

I have spoken to both Celotex and Redland on the correct set up for the roof covering.

If the rafters are partially filled (so you have an air gap) then you use a breathable felt, but there is no need to counter batten. However if it is a complete fill then you need to create a breather gap, so you will have to counter batten the rafters before battening them out for the tiles.

If you are battening directly onto the rafters then you need to create sagging of the felt between each rafter for drainage. There is no need to do this if you are counter battening.

As this is a vaulted ceiling roof I need to create ventilation at the ridges and Redland told me that the whole length needs to be vented using a dry vent system.

The roofer I've been using always pulls the felt as tight as possible and then battens straight over the top. He also said that 2 or 3 ridge vents would be plenty. I don't know if Redland are going overboard, but I'd prefer to do that, than not do enough and it cause problems.

It doesn't give me much confidence in using him again.

Cheers.

If you had traditional felt the ridge vents should be continuous the whole length of the roof.

But if your membrane is breathable you shouldn't need any ridge vents. That said you can never really have enough ventilation and if you're building from new it seems a shame not install them.

 

[SurreyRoofingEstimator]

+1 for FMT

And be aware that with new build the ridge vent system will be very useful to get rid of the moisture trapped in the building materials, mortar, plaster etc.

 

[deuce22]

Thats exactly what I tought. It's best to have more ventilation than not enough.

A technical guy from Redland told me that. I think he emphasised whole ridge vents due to them being habitable rooms below.

I don't like having to second guess or check up on tradesmen, but I have used so many that don't know 100% what the correct way is. A lot of them don't keep up with new things happening and just do what they used to do in the 70s and 80s.

Cheers.

 

[SurreyRoofingEstimator]

Also bear in mind should you be NHBC registered the ridges and any hip ridge now have to be mech fixed instead of / as well as bedded