Dormer on outrigger roof not main roof - PD or planning?

[tpmumtobe]

We have a 5 bed, three storey mid-terrace house. We would like to add an extra bathroom and utility space. We don't need/want to convert the main loft for this; it's too big and would mean trekking up another flight of stairs. We think the most logical thing to do is convert the smaller back loft (ie the roof of the outrigger that sticks out the rear of the house) as it's more or less on the same level of the top two bedrooms.

Most loft conversions, including L shaped dormers, seem to fall under PD. But what we're proposing isn't technically an L shaped dormer because it doesn't connect to the main loft in the way that it might on a two storey house.

We've spoken to eight architects and none of them know for sure!

A couple of neighbours have done something like this but smaller. We don't know if that's because they were restricted by planning or just didn't need something bigger.

I've attached pics. Has anyone done this, or does anyone know whether it would technically be classed as a loft conversion and therefore (as it falls under the 40m3 limit) it will be OK for PD?

Thanks!

I think it’s difficult to tell. When I looked at this a while ago I think you could have done it under permitted development if it was a house, at the rear and not a conservation area and as long as you hadn’t already used up your PD rights on other work (like an extension downstairs). But this was a while ago. Have you looked on your local planning site or asked your neighbours? Also bear in mind that if you use PD for this you might have to apply for planning for any work you do in the future (such as the main loft etc).

All my instincts are saying PP should be required, but looking at the regs I don't think it is clear.
Assuming you are not in a conservation area, the property is a house not a flat, and the outrigger is original to the house not an extension?
The element that concerns me is the height of the dormer above the existing roof on the outrigger which could have a real impact on the neighbours, and on a main roof would not be pd. Similarly if you were proposing a normal extension at that height, PP would be required.
To be certain, and to avoid issues in the future when selling, I would advise submitting an application for a Certificate of Lawfulness. This will give a formal decision by the Council that PP isn't required.

Thanks both. It is a house, it's not in a conservation area and the outrigger is part of the original building. So far we've not done any other work under PD so we still have the full allocation.
The local planning site is clear as mud. Someone shared a PDF of the regs on another thread which was helpful but having combed through it I still can't tell.
Two neighbours on the street have a smaller version of this on their back roof but in both cases the work dates back to pre-planning portal records and before they owned their houses so no insider info to be had there.
The added complication is that we also want to do a side return extension extension to the ground floor. That will need planning because it's over 6m but should gain approval no problems because the neighbours have literally just completed the same.
We can't decide if it's worth trying for PD/cert of lawfulness for the loft separate to planning for the ground floor, or if we should just put the whole lot in under one application.
If we apply for PD and it's rejected, does that make it more likely to be rejected at planning? Would we be better off just going for planning straight up?

If the Certificate application fails, it just means PP is required. There is no impact on the outcome of a full planning application.
Technically the Council should not determine a planning application if the proposal does not require PP, but such things can get overlooked - and then you end up with a refusal for something which technically shout never have been assessed.
If you are making an application anyway, it might be easier to just include everything, but that does run the risk of a refusal as explained above.

Just to say that I think @Seeline is right, I hadn’t seen the plans as looking on a phone but if the roof is going higher than the existing roof then I think you’ll need planning. One of the conditions I remember is that there wasn’t to be anything higher than the existing roof. Does the information you’ve got not say this? In your position I think I’d go for planning on everything and then you’ll keep your permitted development rights for the future in case you or anyone else needs them to do the main loft.

My understanding of the guidelines is that it can't go higher than the main roof, as in the main roof of the building as a whole rather than the roof that's being converted? Guidelines also say anything to the rear can't go higher than the eaves of the main roof, but this doesn't because of the flat roof?

Re: keeping PD rights, how does that work? I'd assumed that by doing an extension of this volume on the back we'd effectively exclude any chance of converting the loft as it would take us over the 40m3 rule, regardless of whether the previous work was done via PD or PP?

You may be right about the highest part of the existing house, I’m not sure but I think you’d want to be certain. Our outrigger roof didn’t go higher than the original peak of that part of the house. I thought you kept the permitted development provided that everything else had been done under planning (but that the size of the permitted development allowed was always referenced to the original building, not the extended one). Again though it’s 10 years since we did our loft! I think if you want an absolute answer you might need to instruct a planning lawyer which to me is probably not worth it- it sounds like you’d probably get the loft under planning anyway if there is precedent with the neighbours already (I can’t tell from what you’ve said above whether what they have is exactly the same or smaller).

This is all super helpful, thank you. Reassuring to know we're not the only ones who can't figure it out! The neighbours have something more like this, where the roof line follows the line of the main roof. It gives space for a small shower room, which would do if that's all we're allowed, but would then mean we'd need to find more utility space downstairs which impacts the plans for the kitchen/side return.

My understanding of the guidelines is that it can't go higher than the main roof, as in the main roof of the building as a whole rather than the roof that's being converted

That is correct - the main roof. But in over 30 years I've never seen what you're proposing, and it just doesn't seem right that the dormer can exceed the height of the outrigger roof considerably, when an normal extension of that height would require PP.

With regards to PD Vs PP, the 40 cubic meters can only be used once regardless of whether that were provided via pd or full planning. If the roof has previously been enlarged, then that volume is deducted from the 40. If any new roof additions result in more than 40 cu.m. being added in total, PP is required.

OK understood. So essentially if this was signed off then any attempts to convert the main loft would need PP and run the risk of being rejected, which is fine, we can live with that.

When you say you've not seen anything like this do you mean being signed off under PD or just being proposed in life in general?

It doesn't seem like a totally bonkers plan to us, I guess the biggest risk is right to light to the neighbours' windows but the height of the party wall won't change that drastically so that side should be fine and the biggest impact light wise will probably be on our first floor rear bedroom. But maybe we're missing something about the bulk of it. It just doesn't seem anymore out of keeping than a normal Lshaped dormer, it's just sat a bit lower down...

I've not seen a dormer on the outrigger, either as pd or as part of an application.

Ok thanks that's useful. Does that mean you think it's unlikely to get approved?

If it's pd it just has to meet the requirements - the impact etc is not relevant.

If it requires PP I think the main issue will be the impact of the increase in height on the neighbours - whether there would be a significant reduction in the light levels, an increased sense of enclosure and the physical dominance. I am assuming the neighbour has a similar outrigger adjoining yours so the impact probably wouldn't be too great. There maybe an impact on your other neighbour depending on layout.

On a construction point - raising the height of the outrigger - will that involve the party wall or will it all within your boundary? PD only applies to development within your boundaries, so if the party wall is involved, PP would be required.

Oh excellent point. Yes it would include raising the party wall slightly (otherwise we'd be building another wall just inside it which seems silly) so yes in that case it would need planning.

And the adjoining outrigger doesn't have any extension on top but the one on the other side (across the side return) which I guess would feel most impact, does which is a plus I suppose.

This has been so helpful, thank you!