Can I install a rear dormer under permitted development 2

[wobbly2]

I've restarted this topic coz the previous one 'https://www.diynot.com/diy/threads/can-i-install-a-rear-dormer-under-permitted-development.505977/' went a bit off topic but I did encourage it.

Getting back to 'The intention is to build a dormer as wide as possibly across the back with its side walls sat on the existing bungalow side walls, its main rear wall sat on the outer leaf of the existing rear wall and its flat roof tucked under the original ridge tiles. The windows will be standard height and size with fanlight and side opening elements to serve 2 bedrooms and a bathroom or 2 bedrooms with en-suite'

One of the side walls may be a Principle Elevation because the bungalow may, subject to the outcome of a Lawful Development Certificate, be on a corner plot. If the side wall is a Principle Elevation would this affect Permitted Development rights? Perhaps the intended location of the dormer side cheek that is destined to be built over or close to that (Principle?) side wall would have to be setback from it? If the dormer side cheek would have to be set back from the side wall how far would the setback have to be for PD? (See drawing).

If the dormer were built then followed by a ground floor rear extension under PD could its roof be pitched so that it tucked under the dormer window sills or would the volume of the rear extension roof be included in the maximum allowance (50m3) for the main roof? (See drawing).


Read more of original topic: https://www.diynot.com/diy/threads/...r-permitted-development.505977/#ixzz5MdqbNfkm

 

[tony1851]

Your dormer alone would not need planning permission, because it does not extend beyond the plane of any roof slope ....which fronts a highway (see B.1(c).
(it's irrelevant that the dormer cheek faces the highway, because there is no existing roof slope facing the highway)
If you combine the roof of the rear extension with the dormer, it would need planning permission because the two works would be counted as one.
A way around that might be to have a gable roof over the extension, with a (lower) ridge running parallel to the main ridge, so that the extension and dormer would not be physically connected.
(You also need to be careful about your proximity to the rear boundary. Although not a Planning matter, there are restrictions on the amount of glazing (doors and windows etc) under Building Regulations to prevent fire spread).

 

[geraldthehamster]

'The intention is to build a dormer as wide as possibly across the back with its side walls sat on the existing bungalow side walls, its main rear wall sat on the outer leaf of the existing rear wall

I believe that to qualify as permitted development, the face of a dormer needs to be set back 200mm from the eaves.

 

[wobbly2]

Your dormer alone would not need planning permission, because it does not extend beyond the plane of any roof slope ....which fronts a highway (see B.1(c).
(it's irrelevant that the dormer cheek faces the highway, because there is no existing roof slope facing the highway)

My understanding from the LPA is that there are additional restrictions to permitted development for properties on corner plots but they did not explain what when asked other than to say it's complicted. My concern is that any side cheek that is built inline with or close to the side wall (Principle Elevation) will be viewed by the LPA as that side wall being extended upwards and thereby not permitted development. on the other hand the side cheek might be viewed as a sideways extension to a principle elevation of less than 50% of original width, thus PD applies?

If you combine the roof of the rear extension with the dormer, it would need planning permission because the two works would be counted as one.

Would this still be the case if the two works were done a year or 2 apart?

A way around that might be to have a gable roof over the extension, with a (lower) ridge running parallel to the main ridge, so that the extension and dormer would not be physically connected.

Initially I don't like the idea but I am warming to it as solution, however:

Presumably it would result in a valley between the two roofs running the length of the bungalow? I'm not keen on horizontal valleys coz they eventually leek.
It would present a second gable to the main road, would that be considered sympathetic to the original structure?
If the original rear wall were removed and if horizontal support beams were not to hang below the ceiling level in the newly created rooms the valley between the two roofs would have to be raised thus potentially connecting the two roof volumes. Could this be a problem under PD?

 

[tony1851]

1. As long as the side cheek is set in a little from the face of the wall - say by leaving one or at most two lines of existing tiles at the verge, that will be OK
for PD. When they say 'it's complicated' it isn't - it's just their way of saying they haven't a clue about the rules.

2. It doesn't matter how many years apart the builds are done, if they join, the later extension will still need planning permission.

3. Can't see any other way of doing it without a valley?

 

[geraldthehamster]

1. As long as the side cheek is set in a little from the face of the wall - say by leaving one or at most two lines of existing tiles at the verge, that will be OK
for PD.

Doesn't the face also need to be set in from the eaves? That is, not on the outer skin of the existing bungalow wall, as suggested.

 

[tony1851]

Doesn't the face also need to be set in from the eaves? That is, not on the outer skin of the existing bungalow wall, as suggested.

Correct, it has to be set back by 200mm; I was just responding to his concern over the side of the dormer facing the highway.

 

[wobbly2]

Doesn't the face also need to be set in from the eaves? That is, not on the outer skin of the existing bungalow wall, as suggested.

As I understand it the dormer face/outer main wall only needs to be a minimum of 200mm back front the bottom edge of the bottom tile i.e. half way across the gutter ish.

1. As long as the side cheek is set in a little from the face of the wall - say by leaving one or at most two lines of existing tiles at the verge, that will be OK
for PD. When they say 'it's complicated' it isn't - it's just their way of saying they haven't a clue about the rules.

2. It doesn't matter how many years apart the builds are done, if they join, the later extension will still need planning permission.

Perhaps the answer is to build the dormer under permitted development then apply for planning permission for a pitched roof rear extension and if they refuse just build it under permitted development using a flat roof, though that might result in having to have boxed in beams (yuck) showing below the ceilings.

 

[geraldthehamster]

As I understand it the dormer face/outer main wall only needs to be a minimum of 200mm back front the bottom edge of the bottom tile i.e. half way across the gutter ish.

The set back is going to take you behind the outer leaf of the existing wall, ie you are not going to be able to build the face of the dormer on it, under PD. The face of the dormer would usually be built onto a steel.

https://ecab.planningportal.co.uk/uploads/miniguides/lofts/lofts.pdf

 

[tony1851]

The set back is going to take you behind the outer leaf of the existing wall, ie you are not going to be able to build the face of the dormer on it, under PD. The face of the dormer would usually be built onto a steel.

https://ecab.planningportal.co.uk/uploads/miniguides/lofts/lofts.pdf

Not quite - and there was always controversy about this.
The original legislation just said that the front of the dormer should be set back 200mm up the slope 'from the eaves'. DCLG stated that this was measured from the outer edge of the tiles/slates.
But a later High Court case (Waltham Forest?) about 4 years ago determined that 'eaves' is not just a line but includes the total overhang of the wall by the roof (the shaded part on the sketch). This is logical, and just exposed the original woolly thinking by DCLG, but it meant that the dormer front should be set back further than DCLG originally intended.
Since that case, they amended the legislation so that the wording is now 200mm 'from the outer edge of the eaves', so we are back where we started.
So where a house has deeply-projecting eaves, it is still possible to build the dormer front directly off the wall and still comply. (Though this can cause other problems such as supporting the floor over the windows, and I agree it is beter to set the front back on a separate steel beam). Theoretically, it would be possible to cantilever the dormer front beyond the wall face - say if the eaves projected 400mm, but the rules now stipulate that the dormer front must not come forward of the wall below.

 

[wobbly2]

I'm a little confuse (not difficult for me) are you saying that the regs say that the arrangement in your first sketch is acceptable but that in your second sketch is more the norm?

My understanding is that the 200mm setback also includes the 50mm or so of tile that overhangs the facia, i.e in your first drawing the 200mm measurement would be 150mm from face of dormer to face of the original outer leaf with the remaining 50mm protruding out over the gutter, or have I got it wrong?

Re: problems supporting the floor over the windows. I'm trying to understand this problem, please could you explain further? Is it because any existing lintel/support over the windows for the existing ceiling joists and roof rafters/load may not be man enough to support the new dormer floor?

 

[geraldthehamster]

I thought the second diagram was to show the situation after the court case that said the dormer face had to be 200mm behind the whole of the overhang, before things reverted to what they are in the first diagram..

 

[wobbly2]

Not sure I follow you Gerald especially as Tony's last sentence reads "but the rules now stipulate that the dormer front must not come forward of the wall below."

 

[geraldthehamster]

The bottom diagram shows a dormer set back 200mm from the whole of the overhang. That is, discount everything that overhangs, and then measure back 200mm. I understood Tony to say that this was briefly the position after a high court case.

The regulations were then amended to refer to the outer edge of the eaves, putting us back where we thought we were previously. That is, measure back 200mm from the edge of the eaves. Depending on the protrusion of the eaves, this might land the wall above the wall below.

In neither case could the dormer front be further out than the wall below. Forward as in further away from a person standing inside the dormer.

 

[wobbly2]

The PD rights technical guide states on page 36 'The measurement of 0.2 metres should be made along the original roof slope from the outermost edge of the eaves (the edge of the tiles or slates) to the edge of the enlargement. Any guttering that protrudes beyond the roof slope should not be included in this measurement. Page 37 has a diagram