I’m thinking that the guttering could overflow over the sides before the water reached a down pipe and waterbutt!
I know a school which was built with an inverted pitched roof … the guttering in the valley proved too shallow to take the amount of water from two pitched roofs and in heavy rainstorms the valley filled with water and penetrated under the roof tiles drenching the children in the assembly hall below … @WonkyWomble’s big brother was one of those children … extensive remodelling of the roof took place before Wonky went to school but even then there were problems in heavy storms.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
I love your painting. Having 'worked' in watercolours I know some of their funny little ways. I'm being polite! On principle I would never deliberately aim water at a building for all the reasons given. One good shower and a couple of stray leaves and you're in bother.
That's a very good concern, @Fairygirl and @Dovefromabove. Normandy can, indeed, be hideously wet!
We had a reverse slope conservatory when we were in the UK and after some teething issues we didn't have a problem.
Maybe wrongly, I don't thing the greenhouse will add much to the gutter, the roof will be approx 1m x 2.5m. If kept clear, it doesn't overflow even in the heaviest downpours - the section of roof that gutter has to cope with is not big. However, I'll certainly look at replacing the gutter with a deep one if that's available, and if there does turn out to be a problem adding second downpipe and/or water butt.
I have looked at so many options for this, and it really is the only place I can see to put a greenhouse at all without it costing the earth, which I don't have to spend. The height of the gutter to ground is approx 2m, the doors that will be the main structure are 2.2m. Without sinking the whole thing 30cm to accommodate a normal slope, which would then itself create the need for more guttering, a butt, etc, I can't see an alternative. I have scratched my little head raw!
Ok, I've just spent a couple of hours looking at this. Following the instructions on a guttering specialist website, I've roughly calculated the effective roof size of the existing roof and then added the 2.5m2 of the greenhouse. It's way under what that size of guttering should be able to cope with, as in about half. And if I compare it with the size of roof on the house and on the other side of the same building, which is much bigger, and where the gutters are fine and only overflowed when we had just bought the house and the gutters hadn't been cleared for a while, I really think I'd be worrying about a remote chance.
To clarify, @plant pauper, the roof will not go up to the wall of the existing building but into the gutter. There is an overhang of approx 45cm so the roof is well away from the wall.
I know there is a (in my opinion low) risk, but this is the plan as I have no other option given the budget. It's this or no greenhouse. So it's a risk I'm happy to take.
Assuming you don't have neighbours called Strawbridge, and depending on what the barn's purpose is, I might suggest a sizeable plastic tank from a Brocante mounted on a platform of breeze blocks INSIDE the barn. By channelling water into it through a modest pipe to catch water from the guttering, a similar pipe back through into the greenhouse with a tap would ensure you can retrieve the water for greenhouse use when required. C'est ca?
Thanks, @nick615. We have a well, not entirely sure how deep it is but with careful usage it kept us going even during the dry of last year. Collecting run off from the barn roof is an option we're keeping up our sleeves if it ever is needed but for now we're ok on that front. Thankfully.
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I know a school which was built with an inverted pitched roof … the guttering in the valley proved too shallow to take the amount of water from two pitched roofs and in heavy rainstorms the valley filled with water and penetrated under the roof tiles drenching the children in the assembly hall below … @WonkyWomble’s big brother was one of those children … extensive remodelling of the roof took place before Wonky went to school but even then there were problems in heavy storms.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
On principle I would never deliberately aim water at a building for all the reasons given. One good shower and a couple of stray leaves and you're in bother.
We had a reverse slope conservatory when we were in the UK and after some teething issues we didn't have a problem.
Maybe wrongly, I don't thing the greenhouse will add much to the gutter, the roof will be approx 1m x 2.5m. If kept clear, it doesn't overflow even in the heaviest downpours - the section of roof that gutter has to cope with is not big. However, I'll certainly look at replacing the gutter with a deep one if that's available, and if there does turn out to be a problem adding second downpipe and/or water butt.
I have looked at so many options for this, and it really is the only place I can see to put a greenhouse at all without it costing the earth, which I don't have to spend. The height of the gutter to ground is approx 2m, the doors that will be the main structure are 2.2m. Without sinking the whole thing 30cm to accommodate a normal slope, which would then itself create the need for more guttering, a butt, etc, I can't see an alternative. I have scratched my little head raw!
To clarify, @plant pauper, the roof will not go up to the wall of the existing building but into the gutter. There is an overhang of approx 45cm so the roof is well away from the wall.
I know there is a (in my opinion low) risk, but this is the plan as I have no other option given the budget. It's this or no greenhouse. So it's a risk I'm happy to take.