House downpipe onto extension mono pitched roof

[CJRatch]

Hi guys,

Thanks for your time.

Just recently had an extension finished, its 6 meters across by 4 meters out. The pitch is 15 degrees with 2 velux windows fitted along with the correct flashing kit, insulation collar and cloaking and the transverse drainage gutter. Cross battened, breathable membrane overlapped at 200mm and tiled with Sandtoft 20/20.

Am I okay to run my house guttering directly onto this mono pitched roof or am I asking for trouble with it being a low pitch to begin with?

If its recommended not to do so has it been heard of before to run the downpipe ontop of the extension roof directly into the extension guttering? Might look a bit naff but could possible paint the pipe the same colour as the tiles?

Any thoughts at all please folks?

Thanks,
Chris

 

[catlad]

I wouldn't do it.

 

[^woody^]

I would

 

[catlad]

Yes well you could get away with being foolish
but me being employed to keep water out of peoples dwelings
then I would say it will be problematic in the long run.

 

[^woody^]

On the basis that a roof should be waterproof in any situation, then what is the problem?

 

[honda]

From my back garden I can see 3 neighboring properties where the downpipe from the house gutter continues across an extension flat roof directly into the gutter. Looks ok to me.

 

[freddiemercurystwin]

This is a pitched roof.

 

[Nige F]

The water may overcome the gutter when it gets there.

 

[honda]

Right

 

[catlad]

When they are testing tiles for their waterproof rating they do it with wind and sprinkler systems, not by pouring water down a tube onto a localised area
ie. flooding the tiles. Some tiles will be better than others for that purpose
wessex for example, But sandtoff 20/20 at such a low pitch if it was one of
my jobs
I couldn't do it.

 

[freddiemercurystwin]

I wouldn't.

 

[^woody^]

When they are testing tiles for their waterproof rating they do it with wind and sprinkler systems, not by pouring water down a tube onto a localised area
ie. flooding the tiles. Some tiles will be better than others for that purpose
wessex for example, But sandtoff 20/20 at such a low pitch if it was one of
my jobs
I couldn't do it.

So how does this localised water running down a roof (like rain), get into the property through the tiles and through the underfelt in a way that is different to blown sprinkled water?

If a roof covering is properly constructed, then no water gets in, because believe it or not, that is the whole point of a roof. Unless the OP's extension is in Atlantis.

 

[catlad]

Well Woody if it had no bearing on things then why would they
have tile ratings? and not to exceed certain rafter lengths?
I understand what you are saying about it shouldn't get through
the felt, and it probably won't for a few years .

 

[^woody^]

What are these tile ratings?

Rafter length limits are for loading nothing to do with water resistance.

The membrane below the tiles will last at least the life of the tiles, and more likely much longer as it is not exposed. So when the inevitable water penetration of the tiles occurs, the underlay membrane deals with it. The point is, that downpipe discharge onto a roof will not have any impact on the weather resistant of the tiles. It can't have.

I draw your attention to gutters on semi hipped roofs, and how they discharge onto ...... the roof.

 

[catlad]

Tile ratings ie. suitable for certain pitches, and the semi hip roof discharge is part of the same roof, not discharging one roof on to another roof.
They realised it was problematic years ago to discharge one roof on to another
without taking any measures to prevent flooding.
Old buildings or church roofs you see it often they will have a shute to take
the water across one roof to the gutter.