Direction of felt

[Jupiter01]

I’m having a flat roof replaced on a single garage and a couple of roofers have had a look at it. Both have suggested a 3 layer felt.

One has suggested that the felt across the fall of the roof with overlapping felt. To a layman this suggested that water would never seep through these joins.

The other suggested that the felt should always run along the direction of the fall with overlaps as it stops water sitting behind each over lap ( when felt is run across).

Can someone pleas advise. Thanks in advance.

 

[noseall]

I’m having a flat roof replaced on a single garage and a couple of roofers have had a look at it. Both have suggested a 3 layer felt.

One has suggested that the felt across the fall of the roof with overlapping felt. To a layman this suggested that water would never seep through these joins.

The other suggested that the felt should always run along the direction of the fall with overlaps as it stops water sitting behind each over lap ( when felt is run across).

Can someone pleas advise. Thanks in advance.

It's all sealed, regardless. Only a failure in their workmanship will cause a leak.

 

[Diver Fred]

1st layer with the fall (bedded into pitch),
2nd layer across the fall from the low end
3rd layer with the fall - hot seal felt - a.k.a 'Torch-On'.

 

[noseall]

To a layman this suggested that water would never seep through these joins.

Correct.
When you consider that say a large roof with lanterns etc, could never possibly benefit form any directional felt, you'll quickly get the picture. There will always be a seam somewhere that goes against the grain, especially the when you consider the edge flashings are done last.

 

[datarebal]

along is preferred