Roof Felt That Important???

[1oddssodds]

Every time I put felt on a roof I have to ask if it is worth it. The stuff is bl**dy expensive and then we put thousands of holes in it. If the job is done properly in the first place then there should be no need for it. Is there a scientific explanation I dont know about or is this one of those sales cons Your opinions on this subject should be interesting.

 

[Deluks]

I take it you're not a roofer? Just do it occasionally?

 

[JohnD]

he's in Argyll. Boarded roof, I think?

 

[Deluks]

Even so, the boarding needs secondary protection.

 

[noseall]

with solid sarking it must seem a little ott regards felt.

down here the felt deals with the dust rubbish, the wind and any water ingress due to tile or lead failure.

i don't know how good solid sarking is at dealing with water ingress but surely this alone is good enough - no?

 

[Kes]

When on hols last month I was watching workers retiling roofs in Atlanta (in stonking heat). The roofs were chipboarded, and were felted before the tiles were applied. The tiles were ashphalt and came in strips of around 6 x 2 'tiles', which were nailed down. Where the felt had bubbles in the tiles would apparently not sit flat so out came a craft knife and the felt was slit so it would provide a flat base. I did wonder about the waterproofing.

Many roofs were being retiled because of hail damage, it had dented the roof and cracked the windscreen of our hosts' car.

 

[noseall]

The tiles were ashphalt and came in strips of around 6 x 2 'tiles', which were nailed down.

shingles.

 

[1oddssodds]

Yes solid wood sarking, felt and then Ballachulish Slate at 80 slates per sq/m with 2 nail holes per slate. This also applies to Spanish Slate when not using battern. I do understand it helping from a dust prevention point of view but waterproofing??

 

[datarebal]

Thats a lot per sqr mtr.. what average gauge do you use?

 

[1oddssodds]

Gauge is 100mm, slate size varys from 120mm to 160mm width. Check out the photo.

Untitled

• 1oddssodds
• 24 Jul 2008
• 1

[/img]

 

[datarebal]

yep a lot a sqr mtr..... nice scaffold! did you get any rain in under the slate before the ridge went on?

 

[redtonybbb]

TonyB-The idea of felt or undersarking is as a secondary barrier,which is better in combination with a roofing batten/as less holes than directly using the membrane directly onto boards.I have to say that there are now better alternatives to felt ie protect A1...breathable membranes that don't rot as felt,not to say that felt is a bad idea.Ingress may occur via capillary action ie pressure and is drawn up the roof slates.(if you look at an old slate you may see the colouration and difference where water has penetrated.A common problem caused by felt is when it rots at the eave,which allows any ingress to rot timber facia and soffit.And it is always better if possible to use tilt fillet to prevent the felt sagging behind the facia.Many years ago slate roofs were torched or backpointed in lime mortar,when felt came in this opperation ceaced generally.With pitched roofs a combination of wind and rain in a certain direction may cause ingress to a roof which is normally dry,and so we have a secondary barrier.

 

[1oddssodds]

Datarebel, we work in the western Highlands of bonnie Scotland, you meant to ask if we got any sun before the ridge went on!! I was fortunate enough that we had little rain over the three week period, temporary cover-ups did the job.