What are the bureaucratic restrictions for PV on a flat roof?

[openspaceman]

Why are you going for planning ???
Anyone who complains just say its permitted development and let them prove different....
George

This is what I did, I just have to wait 3 1/2 years now

[Ken]

Hi, as a placeholder till people who know come along, the general advice for roof edges was 200-300mm. This avoids wind lift on the sides, and rain run off passing over the gutter at the bottom. For the top it's also to stop the higher (raised due to the mounting) PV panels actually be higher than the ridge tiles, which may then require PP as the height and look of the ridge will change ..... leading too ...

for a flat roof, the issue requiring PP may be that you are changing the look if the panels are sloped (typically with pitched mounts or weighted tubs). If the panels are fitted at the same pitch (flat), then it may be OK, but the flatter the pitch, the more the panels will need cleaning, and won't generate as much as say a 30d pitch .....

...... I think?

Yes thats how i remember it particularly the one about the highline. I also remember 100mm as the max distance above the roof be it sloping or not.

We were discussing this 13yrs ago when this was all new but i suspect people are turning blind eyes now. A new house next to me didnt meet some requirement so they built a solar thermal in a box literally sitting on top of the roof.

If the garage is single story a builder type would just do it and if the planners kicked off apply for retrospective planning. This would happen only if a neighbour complained but perhaps you could cut this off by talking to those that might see it. I would fit them at 45deg and the worst that would happen is you have to lay them flatter. Could mitigate it by putting a trim rould the top edge of the garage, this could hide more than one might think as people are looking upwards?

[nowty]

........................ I also remember 100mm as the max distance above the roof be it sloping or not.

Its 200mm from a wall (if doing a facade) or roof slope.

[Smallholder]

I'll admit I didn't do PP for my garage array, taking the route of don't tell, don't make problems.

Could you take an alternative approach and potentially re-roof the garage with a pitched roof, then put solar panels on top?
It could liberate some useful storage space underneath.

That's not a bad shout, but for my situation it would be extremely hard. There are 2 huge roof lights (lanterns I think they are called) in the roof. The roof is also about 20m from south to north, so to add a pitch would massively increase height.

[Smallholder]

Bingo! it was Mr Pablo's pictures, certain there was another near then.

https://camelot-forum.co.uk/phpBB3/view ... 058#p20058

Beautiful, I love this! Thanks for finding it.
My roof layout is quite a bit different, so I am looking at a layout something like this:

[Smallholder]

I'm trying to get a new PV system installed, on a flat roof. I'm about to apply for planning permission, but can't find any solid info online about restrictions in terms of how far from the edge the panels must be.
I assume this is a building regs thing rather than planning permission, but I'll need to be on the right side of both aspects I guess.

Many websites seem to refer to a general rule of panels being at least a metre from the edge, which for my roof will massively reduce the area I can use.

Does anyone else have any experience with this?
Thanks in advance

Why are you going for planning ???
Anyone who complains just say its permitted development and let them prove different....
George

I've had really good experiences with planning in the past, and from what I've heard, the council are generally in favour of 99% of PV projects.

But the main one, is that if I'm going to commit £15k to a project, I want to minimise risk of having to pull it all down because I didn't spent a couple hundred quid getting it properly above board.
It will definitely need planning, as the tilted panels will be above the 200mm allowable distance above the existing roof. The roof is also very visible from the road and from neighbours, and I don't want the bother of getting complaints and knowing it was not above board.

[MrPablo]

I wonder how the roof lanterns affect the current height of the roof. Would the limit be 200mm from the main roof structure, or 200mm above the highest point, aka the top of the lanterns?
That could make a big difference.

[Smallholder]

Hi, as a placeholder till people who know come along, the general advice for roof edges was 200-300mm. This avoids wind lift on the sides, and rain run off passing over the gutter at the bottom. For the top it's also to stop the higher (raised due to the mounting) PV panels actually be higher than the ridge tiles, which may then require PP as the height and look of the ridge will change ..... leading too ...

for a flat roof, the issue requiring PP may be that you are changing the look if the panels are sloped (typically with pitched mounts or weighted tubs). If the panels are fitted at the same pitch (flat), then it may be OK, but the flatter the pitch, the more the panels will need cleaning, and won't generate as much as say a 30d pitch .....

...... I think?

Yes thats how i remember it particularly the one about the highline. I also remember 100mm as the max distance above the roof be it sloping or not.

We were discussing this 13yrs ago when this was all new but i suspect people are turning blind eyes now. A new house next to me didnt meet some requirement so they built a solar thermal in a box literally sitting on top of the roof.

If the garage is single story a builder type would just do it and if the planners kicked off apply for retrospective planning. This would happen only if a neighbour complained but perhaps you could cut this off by talking to those that might see it. I would fit them at 45deg and the worst that would happen is you have to lay them flatter. Could mitigate it by putting a trim rould the top edge of the garage, this could hide more than one might think as people are looking upwards?

I looked at how the system would operate with 45 degree panels, and the space needed between rows would be huge (in order to prevent shading the row behind), so I'd halve the number of panels. In general, it seems to be agreed that about 10-15 degrees is the optimum for flat roof situations, as you get lots of panels on there, and it seems to maximise PV generation per square metre.
This is the layout I'm planning:

[Smallholder]

I wonder how the roof lanterns affect the current height of the roof. Would the limit be 200mm from the main roof structure, or 200mm above the highest point, aka the top of the lanterns?
That could make a big difference.

That's a valid point! My guess it that it would be the existing surface. So for example with a pitched roof, you can mount stuff that increases the height of the roof surface by up to 200mm (allowing plenty for rails and panels), but you could not increase the height of the whole roof to being 200mm above the current apex. But I can check

[MrPablo]

I know you have 20 panels in that plan, but I wonder if it's worth crunching the numbers to see how many panels could be fitted in a back to back east-west configuration on the top roof section.

That way you could eliminate the gap needed to prevent self-shading, still maintain a pitch sufficient for drainage and probably get more generation over the year.