felt leaking

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16 Jul 2010
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Bristol
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hello just felted my roof and will be waiting a week or so before i tile it . But during the bad weather i have noticed rain dripping in through where i have nailed the battens to the raffters its only small leaks but want to sort it before tiles go on any ideals on how to fix it . i have used 65 galv nails and not missed any raffters.
 
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Lift the batten and examine the suspect area.

Did you start your felt at the gutter/eaves and did you overlap by at least 100-150mm as you worked up the roof?

Does your felt sag slightly between the rafters? It should.
 
yes i did it all corectly half people say felt leaks when exposed to bad rain the other half say no it should never get through. the only explanation i can think is its acting like a tent and coming through where the felt is touching the rafters .
 
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1. It could be wind blown and capillary action pulling moisture thro the overlap.

2. Why not water test the area starting low and working high with someone below to observe any results?

3. Doubtful that it's a "tent" effect. Experiment with off-cut's of your felt.

4. What kind of felt is it?
 
its cromar felt breathable . i know the tiles will keep the water out but i was just wondering if any one else had experienced this or am i doing some thing wrong .
 
I notice that it's Cromar felt. My limited knowledge of this felt is that it's for flat roofs. Perhaps your felt is for pitched roofs.

I also noted noseall shouting. The query was not about after tiling, so i addressed the query.

It's commonly agreed that tiles keep water out - but not always. There are quite a few ways of water finding it's way thro any tile or slate covering. How often this happens - whose to say? But once moisture is on the felt, if the felt is not correctly installed, it can lead to roof leaks.
"rain dripping in" thro newly installed felt might indicate incorrectly installed felt.
 
Bitumen felt self-seals at the nails, whereas modern membranes do not - so can leak a little

The idea is to not have too many exposed nails or staples (keep them under the laps if possible), and to sag the membrane so that if water does get behind the tiles, it runs into the sags and not down the top of the rafters and through any nail holes

As the membrane was exposed it may well leak from the nails. Once covered it would tend not to

As to tiles keeping the roof dry, then yes if they are traditional clay or slate. But modern interlocking tiles frequently snap on the interlock runner and water does get through
 
Not uncommon to get the odd drop through. Modern underlays are fine in small amounts of rain but after a few days of it then they will show damp.
It should not be enough to cause visable damp patches.

If your concerned, tile it quick..
 
Just felt over Rafters ... If it was my house I would have sheeted the roof with OSB costing a shade more but worth it IMO, Then felted Battened then tiled. Ventilation fitted as required.
 

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