45° Rule

[ban-all-sheds]

I know it's not a "rule", but I know what I mean.

Where is the horizontal 45° line measured from? I know it's the middle of the nearest window of the nearest habitable room, but in my case that's my neighbour's sliding patio doors, so is the starting point in line with the inside of the opening, the outside, or the glass?

 

[DevilDamo]

Regardless of where it starts, the middle is the middle. I'm not sure what the starting point has to do with it?

 

[tony1851]

If the frame is fixed to the outer skin, take it from the glazing, if that would be more advantageous to you. But it may only be a matter of a perhaps 2 or 3 inches.

 

[ban-all-sheds]

Regardless of where it starts, the middle is the middle. I'm not sure what the starting point has to do with it?

If the overall wall thickness, including all rendering & plaster etc is 30cm (it's not far off, 9" brick + surface finishes each face), then where the starting point is makes a difference of up to 30cm in how big my extension can be.

And that might sound trivial, but its significance is out of proportion to it's actual size.

This is what we want to build at the rear of the house (grey are existing walls, pale blue the new):

A has to be a minimum size, as we want a fridge and freezer there.

B has to be big enough to walk through.

So the depth of the smaller part of the extension has to be a minimum of, I reckon, 1.8m. Clearly we can achieve that by reducing its width. The patio doors & windows we already have, and want to reuse if at all possible, so that Δ of ±15cm plays out in the width of the return on the left of that opening, which makes that small alcove range from something daft, no use to man nor beast, to something where we could put useful shelves/cupboards/etc.

 

[DevilDamo]

The 45 degree line would be taken from the external face so the surface finish and not the centre line of the wall as you have shown. So in that case, it would give you that little more space.

The LPA would look for the position of windows/doors across the face and not how far they're set back from the external face of the wall.

 

[tony1851]

Does it need planning permission?

 

[cjard]

Why does the extension have to be square? Come straight back off the left gable of the house, turn 45 degrees when you hit the red dotted line and proceed until you meet the corner of the kitchen. Big alcove, big door next to fridges..

 

[ban-all-sheds]

The 45 degree line would be taken from the external face so the surface finish and not the centre line of the wall as you have shown. So in that case, it would give you that little more space.

That's good to know - thanks.

Does it need planning permission?

TBH I can't be 100% sure - I've not looked to see what my council says. It certainly would have done before the recent relaxations - PD would only have allowed me to go out 3.6m. I wouldn't be looking to apply until we'd got quotes from builders - no point spending money on PP if we can't afford to build it...

Why does the extension have to be square? Come straight back off the left gable of the house, turn 45 degrees when you hit the red dotted line and proceed until you meet the corner of the kitchen. Big alcove, big door next to fridges..

That would in effect give me a kitchen-diner, which I don't want. Also I do want to keep the patio doors & windows, so they wouldn't be allowed at 45° because they would be facing the neighbour's property.

 

[cjard]

Ok, make the small Square room bigger by going toward the boundaries more then chamfer the corner in line with the red dotted line?

 

[ban-all-sheds]

Could do, although it would make the shape awkward.

I'll re-work things based on starting from the outside face of the wall for the 45° line. I suspect I'll be OK. Can't build right up to the boundary line anyway, as the adjoining property has a conservatory there.

Does anyone know how precise things have to be? If it ends up a few cm out, and 45° goes up by a degree or two will I be in deep doo-doo? Do they come and check with a theodolite? Should we err on the side of caution to ensure it doesn't end up even a fraction over?


I've been wondering what happens in situations where you can't get access to the other property to take accurate measurements.

 

[ban-all-sheds]

Does it need planning permission?

Not for the next few years:

http://www.planningportal.gov.uk/uploads/neighbour_consultation_scheme_guidance_may13.pdf

(AFAIK, no PD rights have been removed by my council).

But I'm even more puzzled now by the 45° rule/guidance/whatever-you-want-to-call-it.

Surely there are virtually no semi-detached houses in the land where a 6m rear extension would not cross the 45° line?

If a valid reason for a neighbour to object is that the extension crosses that line, what's the point of a temporary PD limit of 6m?

 

[DevilDamo]

Agreed. However, the rule is only normally applied to two storey extensions and not single storey.

 

[GKnight]

Agreed. However, the rule is only normally applied to two storey extensions and not single storey.

We ran into the 45% guide (they allow to break it but not by much), the issue we had was 6m and under on PD you ignor the guide. But under planning permission they enforce it. So you can break it if your doing PD and they dont complain, but if you do Planning then they will enforce.

It was stupid for us as we were not allowed to extend under PD 6m x5.2m due to it being more that half the width. But under planning we could go the 5.2 but only 2.5m out!!

In the end we've gone 6m x 4.2m under PD and then plan to do Planning for rear porch as then it wont matter!!!

Daft rules.

 

[freddiemercurystwin]

Agreed. However, the rule is only normally applied to two storey extensions and not single storey.

We ran into the 45% guide

This is not really relevant, all different LA's apply none, some or all of the guidance from the 45° rule. In essence every LA is different so your experience is very unlikely to have any bearing on anyone else, unless you share LA's.

 

[Architexeter]

Hiya,

Basically get it through PD if you can as bizarrly it is less restrictive i.e. no 45 degree guidance etc. As soon as a proposal requires planning permission every man and his dog has something to say about it including planning officers and their design guidance.

Your PD limit is 3 metres projection but as ban-all-sheds says there is now the new Neighbour Consultation Scheme which can permit 6 metres but as the name suggests this requires neighbour consultation. The new scheme apparently requires no fee (PD certificate is £86, Planning £172) but I have not yet submitted an extension that falls within this category so cannot be sure.

Look at your Local Authority's SPD for rear extensions as this 45 degree rule does normally apply to two storey extensions - dont just take the planning officer's word for it as they often dont fully understand it and their PD knowledge can also be awful (some, not all!)

GKnight is getting confused with side extension PD limits, a rear extension can run the entire width of the rear of the property BUT if it links to a side extension or goes past the side of the original house then yes, the half width of original dwelling width kicks in.