box gutter/valley advice - best way to form and cover?

[RomanAbramovich]

recently had a small extension built with roof carcassing, the roof is hipped and sits parallel to another small hipped roof. i need to form something like a 'box gutter' to drain surface water away but obviously there is no fall at the moment.

(roof carpenter told me it needs a 'box gutter' before claiming to have flu and is now onto another job)

what is the best way to form this gutter? he mentioned 18mm ply, stepped every 1.5m and with a 1 in 40 fall. i was up there today and with A 2.6M linear run the width of the gutter at its highest point would be around 2 feet, which is shed loads of (expensive) lead!

heard glass fibre kits are also an option?

to be honest i'm not sure what this type of valley/gutter is officially called?!

cheers.

 

[Zeberdee]

Your best bet is to get the ''valley''/Water Run-Off'' done in EPDM.

It's Rubber that can be done in 1 sheet, Ideal for what your after TBH.

1 Single sheet all the way. NO JOINS! NO LEAKING POINT!!

 

[RomanAbramovich]

thanks - do i still need to form the valley with ply first?

 

[BethesdaSlate]

The best job, by far, would be to do it in lead.
1 piece of Code 7 lead will be fine for 2.6lm, 1:80 fall.
Maybe the more expensive option, but if done properly you will never need to think about it again.
It's the correct material for this detail.
Your leadworker should be able to advise on (and fix) the timber detailing required, if he can't then I wouldn't use him.
Lead cost - 1 roll Code 7 3mx900 = approx £300 inc vat
I'm assuming you can get away with max sole width of 500mm wide
Labour = 1 Lead man 1day
Plus a bit more for underlay, nails, oil, timberwork.

 

[Zeberdee]

thanks - do i still need to form the valley with ply first?

Ply or OSB to be honest.

Lead will be expensive, EPDM Rubber wont be.

EPDM Will be in 1 single strip, No joins etc.

 

[Alastairreid]

If diy do it in EPDM otherwise the best option would be lead.

 

[RomanAbramovich]

The best job, by far, would be to do it in lead.
1 piece of Code 7 lead will be fine for 2.6lm, 1:80 fall.
Maybe the more expensive option, but if done properly you will never need to think about it again.
It's the correct material for this detail.
Your leadworker should be able to advise on (and fix) the timber detailing required, if he can't then I wouldn't use him.
Lead cost - 1 roll Code 7 3mx900 = approx £300 inc vat
I'm assuming you can get away with max sole width of 500mm wide
Labour = 1 Lead man 1day
Plus a bit more for underlay, nails, oil, timberwork.

thanks for the detailed advice, looking at the job the max sole width might well be greater than 500mm, but this might be due to the fall i've anticipated, which is 1:40 - you mention 1:80, is that fall considered suitable for this type of gutter/valley by the BCOs? tbh, reducing the fall to 1:80 will make the job easier and reduce the sole plate width. also do i need to form any steps for the lead? carpenter mentioned max 1.5m run for each lead sheet, each step being 25mm in height - in which case i would need to form 1 step - is this really necessary? Cheers.

 

[RomanAbramovich]

If diy do it in EPDM otherwise the best option would be lead.

thanks, any can you point me to a site that sells this rubber product in kit form?

also seen some glass fibre kits that look promising, couple of rolls of material and a a tin or hardner/contact adhesive - anyone had experience of this product for a gutter/valley of this type? cheers.

 

[ladylola]

1:80, is that fall considered suitable for this type of gutter/valley by the BCOs? tbh, reducing the fall to 1:80 will make the job easier and reduce the sole plate width. also do i need to form any steps for the lead? carpenter mentioned max 1.5m run for each lead sheet, each step being 25mm in height - in which case i would need to form 1 step - is this really necessary? Cheers.

Yes 1:80 is standard for lead work, lenght of bays depends entirly upon the code used, I,ve been on a job where we couldn't introduce steps and ended up with a bay over 5m done in code 12! As beths says code 7 in one piece. As a rough rule of thumb we have always worked at 23 square feet as being the maximum size of sheet. I don't really know where that figure came from but we've always "used" it. Smaller bays are in many respects a good idea, it will reduce the effects of thermal expansion and contraction.

If you end up having steps or drips as we tend to call them then 25mm is not really enough, we work on a 65mm minimum

 

[RomanAbramovich]

1:80, is that fall considered suitable for this type of gutter/valley by the BCOs? tbh, reducing the fall to 1:80 will make the job easier and reduce the sole plate width. also do i need to form any steps for the lead? carpenter mentioned max 1.5m run for each lead sheet, each step being 25mm in height - in which case i would need to form 1 step - is this really necessary? Cheers.

Yes 1:80 is standard for lead work, lenght of bays depends entirly upon the code used, I,ve been on a job where we couldn't introduce steps and ended up with a bay over 5m done in code 12! As beths says code 7 in one piece. As a rough rule of thumb we have always worked at 23 square feet as being the maximum size of sheet. I don't really know where that figure came from but we've always "used" it. Smaller bays are in many respects a good idea, it will reduce the effects of thermal expansion and contraction.

If you end up having steps or drips as we tend to call them then 25mm is not really enough, we work on a 65mm minimum

this is very good advice, many thanks.

ironic really that my approach to this job has been governed by roof carpentry and forming, just had an 'ok' over the fone from the roofer/lead man that he'll come for a day to dress it when ready. the carpenter mentioned code 4 lead, which i'm familiar with myself from dressing valleys on hipped roofs, and i guess the carpenter only knows about the restrictions governed by what u can do with code 4 (ie 1.5m run, steps etc) - so you lead guys have enlightened me big time, making me aware of alternative (and simpler) solutions to the job.

one last question.....the 'mouth' of the gutter, it's lowest point, how wide does the sole need to be at this point? this will be the narrowest part of the gutter, so need to ensure debris doesn't block it over time - is there a standard minimum width for it? cheers.

 

[RomanAbramovich]

...example of the gutter/valley setup i'm attempting to describe/create:

box gutter valley trough

• RomanAbramovich
• 5 Mar 2011
• 1

[/img]

 

[ladylola]

I'll stand to be corrected on this one, I don't think there is a minimum as such be we always try to get it as large as possible and 150mm at least, although saying that there have been times when it hasn't been possible to get larger than 100mm

 

[BethesdaSlate]

Hello

The Code 7 lead would indeed be fine in one piece at that length. As stated above you would only need steps when using a lighter code lead and thus reducing its maximum length.

So no steps or joins required.

Agree with the 150mm width for the outlet end, with the tiles or slates kept at least 75mm vertical height off the 'sole'.

 

[timbo10]

lead? loads of work. line the gutter with moisture resistant 18mm t and g flooring and have it fibreglassed. drop as low as 1:120 fall depending on the roof area and don't step it. easy

 

[yorkie1969]

If you wanted to do it in one piece of lead you would need code 8 at that length. Code 7 can only go in up to 2.5 linear metres. The problem with this is that the roll of lead would weigh upwards of 200 kilos (around 30 stones).

That said, if you do not have the room to be able to introduce a step which would have to be 55mm high you could use 2 pieces of code 5 lead with an expansion joint welded in the middle. This stuff has been on the market over 25 years now and I have never seen it fail yet.

I am a leadwork contractor and if it was me I would use the step option first and the expansion joint if that wasn't feasible.

Good luck.