Calculating roof volume- ?eaves

[Claref]

Hi, my planners tell me I should measure from the eaves to calculate roof volume but I dispute this since there is nothing in the Planning Portal or GPDO to suggest this and it seems to use the walls as the fixed point of measurement. I'd prefer the latter since it gives me an extra 5m3.

Can anyone illuminate the situation definitively? My planners say they will have to refer to case law.

Many thanks.

 

[D_Hailsham]

Why do you need to know the roof volume?

 

[freddiemercurystwin]

External volume I believe.

 

[^woody^]

Calculate roof volume for what purpose? Things differ depending on what you are doing

 

[Claref]

Its for a dormer - there have been previous additions to roof space it is vital I keep within the 50m3 allowed under PD as I would not get PP for this.

There is no indication either under GPDO or the Planning Portal for using eaves as a point of measurement. Indeed, both seem to indicate using the wall as the external measurement since it is a fixed and immovable point - unlike fascias and soffits.

I believe there is some case law arguing this point - can anyone point me towards the relevant cases?

Many thanks

 

[^woody^]

I can't understand the problem.

Are you saying that your proposed dormer is going to have some sort of massive eaves which will take you over the PD limit? If so just redesign them

External measurements are required to work out the additional volume though, so new eaves would be included

 

[Claref]

I may not be understanding you but the problem is when calculating volume it differs by 5m3 if using the eaves as a reference point since the eaves are wider than the wall (I'm not arguing the height other than at the apex of the roof).

This matters to me because it means I will not be able to achieve my plans under PD if I do not have the additional volume - I am at the PD limit.

I understand it is external measurements.

All I am trying to find out is if the calculation of volume MUST be eaves to eaves or if wall to wall can be argued as a valid reference point for measurement.

If so I'd really like some examples to send to my planners to support my case.

Hope you can help.

 

[DevilDamo]

All I am trying to find out is if the calculation of volume MUST be eaves to eaves or if wall to wall can be argued as a valid reference point for measurement.

It's a combination of both. Measure the "external" area of the walls and then measure the "external" area of the roof (inc. eaves).

 

[^woody^]

I may not be understanding you but the problem is when calculating volume it differs by 5m3 if using the eaves as a reference point

You can't have 5m3 of eaves on your new dormer surely?

PD allows dormers to increase the roof volume by 40 or 50m3 depending on the house type

So are you just measuring the dormers or the whole roof?

 

[D_Hailsham]

The eaves count!

Someone else had the same problem, appealed and lost.

Read Planning Appeal

 

[^woody^]

The eaves count!

The eaves may count when measuring roof volumes, but do they count to the OP when all he needs to measure is the additional volume of what he is adding to the roof?

The OP needs to be clear exactly what he needs to measure

 

[D_Hailsham]

The eaves may count when measuring roof volumes, but do they count to the OP when all he needs to measure is the additional volume of what he is adding to the roof?

The problem is that some of the permitted 50m³ has already been used up.

there have been previous additions to roof space

If these additions added 30m³ to the original house, Claref now has only 20m³ left for the dormer window. The problem she(?) has is calculating how much has already been added.

The regulations definitely say that it is the external volume which is relevant. So porches etc are counted as well as chimneys which protrude from the main wall of the house.

The problem seems to be: is the external air space between the rafters counted as part of the volume? If they are exposed, I would say 'no', but if there is a soffit covering the exposed rafter ends, I would say 'yes'. (I am using the chimney as the basis for this.)

 

[^woody^]

The regulations definitely say that it is the external volume which is relevant. So porches etc are counted as well as chimneys which protrude from the main wall of the house.

The additional volume calc applies to additional roof alterations only, not porches or anything else

If there are previous roof alterations then surely those are easy to work out, as it is just the bits which stick out of the original roof?

It would certainly be going some to get more than 40 or 50m3 of roof alterations - that's like two full length dormers front and back, or a massive extension cutting into the roof

 

[big-all]

my reading is he want want to go h x w x l and multiply then add on the 40/50 square as appropriate he is so close that if he removes the volume removed by the slope off the roof he will not have enough origional volume

 

[D_Hailsham]

The additional volume calc applies to additional roof alterations only, not porches or anything else.

You are quite correct. The original 1995 Legislation only gave GPD permission for additions to the roof space if the volume of the original house did not increase by more than70m3 or 15%. This was amended in 2008 to increasing the volume of the original roof by more than 50m3. (Detached house figures quoted.)

If there are previous roof alterations then surely those are easy to work out, as it is just the bits which stick out of the original roof?

You would have thought so.

It might be worth checking if the local Planning Authority has any documentation relating to the original roof extension. Previous owners may have applied for planning permission, even if it wasn't legally required. That way they would have documentary proof that the alteration was OK when it came to selling the house.

Most local authorities have searchable databases of Planning Applications etc.