Fascia,gutter, eaves

[Auchlossen]

I am using scottish larch to provide a fascia, verge with alu box gutter attached, on a small building [garage/studio] of 6x6m2

The contractor has used a 3" 75mm box gutter, right on the face of the fascia, which in turn is on the face of the wall, and is resisting changing it. He says it is quite adequate for a small roof.

My slater says it is not good enough:

• slates must overhang 2" 50mm to avoid capillary creep underneath
• slates must have 2" 50mm beyond to gutter outside edge to avoid water overshooting

Stones posted on another topic:
 

Quote

 

A 50 mm slate overhang is critical (and insisted upon by BC) and ensures water drips off the edge of the slate.

 

I will welcome advice from the community.

[MikeSharp01]

If I am imagining this correctly, drawing might help, the tiles will be overhanging the first 50mm (2 3rds of 75mm) of the gutter width which is maybe what the slater is trying to tell you. That does not feel right normally you want the tiles to overhang the first third maximum. This ensures that fast run off hits the gutter and does not overtop it as might happen with your scheme, if I have it clear in my mind.

Edited November 4, 2016 by MikeSharp01

[Barney12]

2 hours ago, MikeSharp01 said:

If I am imagining this correctly, drawing might help, the tiles will be overhanging the first 50mm (2 3rds of 75mm) of the gutter width which is maybe what the slater is trying to tell you. That does not feel right normally you want the tiles to overhang the first third maximum. This ensures that fast run off hits the gutter and does not overtop it as might happen with your scheme, if I have it clear in my mind.

 

That is how I had interpreted it.

 

Ideally you want to the tile to be no more than 50% into the gutter but I'm inclined to agree with your contractor that the run off on a relatively small roof area would in most cases not cause an issue provided you're not in an exposed (wind or rain) area. BUT, you would be justified in demanding a 100mm (or 125mm) gutter as its not "right". I guess it depends how much you want to argue with your contractor (and how much the job is costing).

[daiking]

I have this very problem.

 

Only a short section of gutter but the few tiles that extend too far cause the water to cascade to the ground over the gutter. Bad in heavy rain and this is only a small roof.

 

If I'm home, its dry enough to get on the roof and daylight at any time in the next 6 months I might be able to get a photo to show how little a gutter 'overhang' causes an issue.

Edited November 4, 2016 by daiking

[Crofter]

Presumably roof pitch plays a part- hard to imagine water running 50mm uphill on the reverse side of slates on a 45 degree roof?

[Temp]

I've had the same problem. In heavy rain the water overshoots the gutter if you aren't careful with the geometry. 

 

Google found this..

 

http://www.ribaproductselector.com/Docs/4/21084/external/COL521084.pdf

 

See page 11 for a drawing and..

 

 

Quote

To ensure the slates hang 50mm into the gutter, the tails of the first course of slates should be offered up to run parallel with the under

eaves courses.

 

PS In my opinion the drawing shows the gutter too low. Will have too much overshoot.

Edited November 4, 2016 by Temp

[Crofter]

If I could just hijack this thread for a second...

 

How much standoff distance should I allow for between fascia and gutter? I'm hoping to order my steel roof sheeting next week and really want to avoid cutting it on site, so need to get the length bang on. Obviously I don't have the guttering ordered yet as it would just be lying around getting in the way.

[ProDave]

My gutter brackets screw directly to the fascia and allowing for the thickness if the brackets,it's probably 10mm from the fascia to the edge of the gutter.

 

funny enough I am looking to order my box profile roofing soon so we need another thread to compare noted and see who can get the best deal. But my thinking is to base my measurements on the roofing overhanging the fascia by 50mm, AND at the ridge, the two sheets not quite meeting with say a 50mm gap between them. That gap will be covered by the ridge piece, but will also allow a bit for "adjustment" of the final eaves overhang if that makes sense.

 

Let's discuss that further on another thread so as not to take this one off topic.
 

[Auchlossen]

Thanks all.

The roof pitch is shallow, about 25deg, with IKO slates.

I guess this means that capillary regress of water up the underside of the slate is the more likely,

but also that water will shoot down the slope more slowly than on a 45deg roof.

Thanks for the link to the RIBA/CUPA Slate guidance, which affirms the 50mm overhang for the slates.

I will discuss this with contractor tomorrow.