Solar Panels on outbuilding

tetrarch

I have been planning to put solar panels in/on to a new roof but my Local Authority are "Planning" to thwart me.

I'm already 2 years into the maelstrom that is planning an extension onto a 1924 house in the green belt. I was hoping to get rid of a 1970's pitched roof on a hideous brick extension, but so far the LA (and the Planning Inspectorate) are saying "non"

The above picture is oriented per google maps so the orientation is near perfect. The original plan was for the yellow area to house in-roof solar on a new roof with a 43-deg pitch.

My new idea is to mount panels on the red area. This is an outbuilding with an ~15-deg pitch which is about 95% of optimal if my research is accurate. This are is pretty exactly  3m x 10m so I could get 15 2m x 1m panels on.

Issues for consideration:

Weight:     At present the roof is just 12mm OSB. I'm not sure that this enough, but I could always replace/overlay with plywood if necessary
Shading:   As you can see there is some vegetation directly to the South and this is on the boundary line. I am on very good terms with my neighbour and I would happily pay for new planting and a more aesthetically pleasing treatment of the currently tatty rear of outbuilding. 
Planning:  Are there any rules regarding panels and the boundary?

Given that access is easy, I'm even thinking of self-installing but with an electrician to do the important bit.

I would welcome any advice that anyone has regarding my ideas - especially from any solar DIY'ers

Regards

Tet

QrizB

tetrarch said:
Issues for consideration:

• Weight:     At present the roof is just 12mm OSB. I'm not sure that this enough, but I could always replace/overlay with plywood if necessary
• Shading:   As you can see there is some vegetation directly to the South and this is on the boundary line. I am on very good terms with my neighbour and I would happily pay for new planting and a more aesthetically pleasing treatment of the currently tatty rear of outbuilding. 
• Planning:  Are there any rules regarding panels and the boundary?

Given that access is easy, I'm even thinking of self-installing but with an electrician to do the important bit.
I would welcome any advice that anyone has regarding my ideas - especially from any solar DIY'ers

That's a well-oriented roof! Ffiteen 400W panels would be 6kWp? A useful size of array.

Taking your points in turn:

• Weight: what's under the OSB? Anything? Would you walk/stand on it happily? I share your concern re. strength. In theory part of an accredited installer's MCS training includes enough strucutural engineering to assess a roof ...
• Shading: all you *need* is for the vegetation to be cut back to the gutter line and kept there. Replanting and/or prettifying the back of the structure might be a useful angle to sell your neighbour on the idea, though!
• Planning: the page at Planning Portal night be useful. At first glance your installation might be permitted development (so no planning permission required) but the devil's in the detail.

If you plan to export and be paid for it, I think you'll need a MCS Certificate which will mean an accredited installer not just an electrician.

Raxiel

If the OSB isn't strong enough to support the panels and has to be replaced, some installers offer 'built in' installation of panels, where the existing roof surface (tiles typically) is removed and the panels take their place. Can look neater than the usual 'on rails' approach, although the lack of airflow to the back of the panels can mean they get a bit hotter.

More work and expense than a traditional setup, but if you're having to replace the roof anyway...

tetrarch

The roof is just a loose laid sheet of EPDM and the OSB boards are screwed onto 600mm centred 4x2's so plenty stron enough as a structure. Easily removeable so upgrading to 18mm ply would be a trivial exercise if required

Thanks for the advice

Martyn1981

tetrarch said:

The roof is just a loose laid sheet of EPDM and the OSB boards are screwed onto 600mm centred 4x2's so plenty stron enough as a structure. Easily removeable so upgrading to 18mm ply would be a trivial exercise if required

Thanks for the advice

Really, really, really sorry to be 'that guy', but!

4x2 rafters with 600mm centres will be fine for supporting the weight. [Isn't it funny how building terms mix imperial and decimal, that's exactly how I would have referred to it.]

But, the real problem, I suspect, won't be holding the roof up, but holding it down, due to the potential additional windlift. So worth checking to see how the rafters are anchored, are they attached securely to a wall plate, or similar, and is the wall plate then securely attached to the walls using straps.

This was brought home to me about 10yrs ago when two things happened. Firstly I helped a builder friend build the roof on our side extension/garage, and was shocked at the amount of fixings needed to hold a roof 'down'. And secondly, when during a storm the garage roof from a neighbour 6 houses down, landed in the garden of the house next door to me. The whole roof (7m x 3m) upside down, box profile steel, with all rafters and wall plates attached, and a row of strip lights .... wow.

I helped the owner (previous owner?) whilst she called for her son to come home, and shut down all the electrics to the garage. Whilst there, I really couldn't see how the roof was attached, other than the wall plate being screwed down onto the walls.

Nothing scary nor expensive, just the necessary 'belt and braces'.