felt question

[dtl]

Hello,

I am having a roof re-slated.
It is an old house; field stone wall with rubble infill, sarking board below slates.

The roofer has dobbed mortar along the bottom of the roof on top of the roofing felt, he has then pressed the bottom course of slates into the mortar.

This seems daft to me, I thought that the felt was meant to be able to drain in the event that water gets under the slates?
By building a wall of mortar at the bottom of the felt he has prevented the felt from being able to drain.

Any thoughts?

Thanks

 

[^woody^]

Is your roofer 200 years old and stuck in his ways?

We tend to use a timber tilting fillet or plastic eaves combs nowadays

But TBH, that's how they used to do for years and it lasted if done properly

You will get little if any water getting past the slates, so don't worry about drainage

 

[Blagard]

You will get little if any water getting past the slates, so don't worry about drainage

Blimey Woody this is a new tack for you.

dtl,

I agree with woody, that it was an old fashioned way of doing eaves, really before the advent of a felt underlay. It was also carried on after felt was introduced in a similar way they also did it to concrete profile tile roofs.

However at risk of upsetting Woody again, Mortar should no longer be applied direct to the felt. There is nothing wrong with a mortar bed providing there is a means for the felt to drain. So this is usually achieved with a propriety plastic product. I would not be happy about a "mortar dam" at the bottom. If you do not have an modern eaves detail with an overhang I would be even more concerned.

The felt amongst other things acts as a secondary line of defense for when either you loose a slate or two, or in extreme conditions. It will not normally get wet at all. Hopefully you should never have to rely on it for water ingress protection.

 

[dtl]

Hello,

Thanks for the responses.

Bsaed on the feedback, I have just spent a couple of hours with a piece of dowel poking drainage holes through the mortar dam in between each of the lower slates.

 

[Blagard]

Based on the feedback, I have just spent a couple of hours with a piece of dowel poking drainage holes through the mortar dam in between each of the lower slates.

Well that's an unusual solution, but you have now got some escape route for water if it is ever needed. I think you can sleep better for that.

 

[dtl]

...I've just noticed something else;

When he has dobbed the mortar on he has made no attempt to keep/make the top of the wall straight, so the first course of slates is not straight and it looks a mess.

What is the easist way for him to get under the bottom course of slates to resolve this.

 

[joe-90]

You've probably rucked up the mortar poking dowel into it. Any warranty will now be null and void. I doubt he'll want to know.

 

[dtl]

I think you are implying upset the bottom course of slates when a poked a hole with a 5mm dowel.

I did not.

The most uneven part of the roof is at high points, where there is too much mortar.

My question is how can he fix this?