SIPS building and permitted development?
Discussion
I want to build a workshop in my garden (4mx6m roughly) and I was thinking of using SIPS. I don't think it will be too dissimilar in terms of cost compared to a timber frame building. Main reasons for a SIPS building is speed of construction and insulation. They are also supposedly stronger than a timber frame building. A few questions regarding that:
1. Just how much stronger is a SIPS building made of 100mm panels compared to a timber frame building made of 4x2's and osb sheets?
2. How much weight can I hang from the roof internally?
3. Would it be strong enough to support a beam trolley with a 250kg engine hanging off it?
My second query relates to permitted development. 30m2 is allowed, but it can only be max 2.4m in height. It also has to be 1m away from a boundary unless "constructed of substantially non-combustible materials".
4. I live on a hill and the far end of my garden is lower than the front. I can't find the relative information on the permitted development website, but i've read that the 2.4m height is measured from the highest point of the curtilage of the house. So assuming the far end of my garden (where I want to place the workshop) is 1m lower than the patio, I can effectively have a building with a height of 3.4m. Is that correct?
5. I saw someone building a shed on youtube. They were right up against a boundary, but claimed that cladding the shed on the boundary sides with steel sheeting would mean it complies with the regulation. Permitted development regs doesn't go into much detail about this so it seems like a bit of a grey area. Thoughts?
1. Just how much stronger is a SIPS building made of 100mm panels compared to a timber frame building made of 4x2's and osb sheets?
2. How much weight can I hang from the roof internally?
3. Would it be strong enough to support a beam trolley with a 250kg engine hanging off it?
My second query relates to permitted development. 30m2 is allowed, but it can only be max 2.4m in height. It also has to be 1m away from a boundary unless "constructed of substantially non-combustible materials".
4. I live on a hill and the far end of my garden is lower than the front. I can't find the relative information on the permitted development website, but i've read that the 2.4m height is measured from the highest point of the curtilage of the house. So assuming the far end of my garden (where I want to place the workshop) is 1m lower than the patio, I can effectively have a building with a height of 3.4m. Is that correct?
5. I saw someone building a shed on youtube. They were right up against a boundary, but claimed that cladding the shed on the boundary sides with steel sheeting would mean it complies with the regulation. Permitted development regs doesn't go into much detail about this so it seems like a bit of a grey area. Thoughts?
A SIPS panel is basically a closed panel timber frame and structurally there is little difference. It’s down to the size and quality of the framing material. Same materials = basically same strength. However, if you are buying SIPS off the shelf you can’t customise it as you could timber frame, especially if you are stick building.
In terms of load. 250kg is a lot. Where we are manufacturing floor cassettes for care homes etc that have hoist tracks a fair amount of extra material goes in. Unfortunately, I can’t give you the detail as I have engineers and technical managers that sort that stuff out.
In terms of load. 250kg is a lot. Where we are manufacturing floor cassettes for care homes etc that have hoist tracks a fair amount of extra material goes in. Unfortunately, I can’t give you the detail as I have engineers and technical managers that sort that stuff out.
SIPs are great for what they are, but it’s quite involved to add additional strength to standard panels. I have no idea what the engineering tolerances of a SIP is but I doubt you’d be able to hang 250kg off one in a roof without significant deflection. Without re-engineering the SIP with additional strength, you would probably have to build a timber or steel frame inside the SIP enclosure.
I built a garden room and I needed a steel goalpost arrangement for some doors, and that with some other details meant I went down the stick build route rather than SIPs. There’s a thread on here about the build, I can dig it out if you’re interested.
You’re incorrect on point 4 about heights; it’s the highest original ground level adjacent to the building that you take, not the curtilage. So if the site you want to build on is sloping, it can work to your favour (as does understanding the exact points on the building that PD takes for height calculations).
Again, my site for the above building was sloping so I was able to build 600mm higher than usual under PD. Again, there was a thread on here about the principles, discussed in detail with a planning consultant who used to frequent this forum, and it was all ratified with Lawful Development Certificate by the Council.
I built a garden room and I needed a steel goalpost arrangement for some doors, and that with some other details meant I went down the stick build route rather than SIPs. There’s a thread on here about the build, I can dig it out if you’re interested.
You’re incorrect on point 4 about heights; it’s the highest original ground level adjacent to the building that you take, not the curtilage. So if the site you want to build on is sloping, it can work to your favour (as does understanding the exact points on the building that PD takes for height calculations).
Again, my site for the above building was sloping so I was able to build 600mm higher than usual under PD. Again, there was a thread on here about the principles, discussed in detail with a planning consultant who used to frequent this forum, and it was all ratified with Lawful Development Certificate by the Council.
Edited by PhilboSE on Sunday 10th August 07:20
Edited by PhilboSE on Sunday 10th August 07:21
Re point 5 and building materials, there isn’t a precise definition of “substantially”. Fundamentally you can do what you want, until it’s challenged. If so, you’ll have to justify the materials in a way rather more detailed than “I saw a bloke on YouTube do it s as nd he says it was ok”. Easiest thing is to build 2m away from the boundaries, if you can.
rinseout said:
5. I saw someone building a shed on youtube. They were right up against a boundary, but claimed that cladding the shed on the boundary sides with steel sheeting would mean it complies with the regulation. Permitted development regs doesn't go into much detail about this so it seems like a bit of a grey area. Thoughts?
The YouTuber needs to understand the difference between “constructed from” and “clad in”. Steel is an incredibly good conductor of heat.There is no steel cladding on the market that will stop a combustible building from catching fire if exposed to the heat of a fire.
smokey mow said:
rinseout said:
5. I saw someone building a shed on youtube. They were right up against a boundary, but claimed that cladding the shed on the boundary sides with steel sheeting would mean it complies with the regulation. Permitted development regs doesn't go into much detail about this so it seems like a bit of a grey area. Thoughts?
The YouTuber needs to understand the difference between “constructed from” and “clad in”. Steel is an incredibly good conductor of heat.There is no steel cladding on the market that will stop a combustible building from catching fire if exposed to the heat of a fire.
Personally, I'd build the shed however you wish to give you the result that you desire. Timber frame is probably easiest if you have space to construct the sides on the floor but sips, especially if a kit will not be much different. I'd then just add a steel goal post internally exactly where I'd want to be hoisting and engine out but to be honest, using an actual mobile engine hoist seems more sensible as you can then move the engine away from the car opposed to having to move the car from the engine etc?
PhilboSE said:
You’re incorrect on point 4 about heights; it’s the highest original ground level adjacent to the building that you take, not the curtilage. So if the site you want to build on is sloping, it can work to your favour (as does understanding the exact points on the building that PD takes for height calculations).
Again, my site for the above building was sloping so I was able to build 600mm higher than usual under PD. Again, there was a thread on here about the principles, discussed in detail with a planning consultant who used to frequent this forum, and it was all ratified with Lawful Development Certificate by the Council.
Can you explain what you mean by highest original ground level? Again, my site for the above building was sloping so I was able to build 600mm higher than usual under PD. Again, there was a thread on here about the principles, discussed in detail with a planning consultant who used to frequent this forum, and it was all ratified with Lawful Development Certificate by the Council.
I have measured my patio and the highest point is around 1.2m higher than the ground at the far end of my garden. Am I to assume adjacent in this sense means directly opposite, and that my patio would be classed as being adjacent?
Pic for reference:
Any ideas on what to search for to dig up that thread with the planning consultant?
Edited by rinseout on Monday 11th August 14:27
DonkeyApple said:
Personally, I'd build the shed however you wish to give you the result that you desire. Timber frame is probably easiest if you have space to construct the sides on the floor but sips, especially if a kit will not be much different. I'd then just add a steel goal post internally exactly where I'd want to be hoisting and engine out but to be honest, using an actual mobile engine hoist seems more sensible as you can then move the engine away from the car opposed to having to move the car from the engine etc?
My main concern is speed of construction. I'd insulate and clad the shed internally anyway, so a SIP building removes a lot of time spent doing so.It's not paramount that I have a beam trolley, just a nice idea. I guess I could always erect a steel structure inside at a later date if required.
rinseout said:
Can you explain what you mean by highest original ground level?
I have measured my patio and the highest point is around 1.2m higher than the ground at the far end of my garden. Am I to assume adjacent in this sense means directly opposite, and that my patio would be classed as being adjacent?
Pic for reference:
Any ideas on what to search for to dig up that thread with the planning consultant?
It's the (pre-existing) ground level at the point where the outer walls of your building sit. So you only really get a gain if the location for your building is on a slope. I dug out the old threads, had to go back a while...I have measured my patio and the highest point is around 1.2m higher than the ground at the far end of my garden. Am I to assume adjacent in this sense means directly opposite, and that my patio would be classed as being adjacent?
Pic for reference:
Any ideas on what to search for to dig up that thread with the planning consultant?
Edited by rinseout on Monday 11th August 14:27
Exploratory questions while I established the principle...
Later discussion on actual outcome and planning sign off (LDC) on page 2
"Equus" is a professional planning consultant, but no longer posts here.
rinseout said:
Can you explain what you mean by highest original ground level?
I have measured my patio and the highest point is around 1.2m higher than the ground at the far end of my garden. Am I to assume adjacent in this sense means directly opposite, and that my patio would be classed as being adjacent?
Pic for reference:
Any ideas on what to search for to dig up that thread with the planning consultant?
As Philbo says, tread carefully on "adjacent", if they want to be awkward it means directly next to/adjoining the building that is being questioned. I have measured my patio and the highest point is around 1.2m higher than the ground at the far end of my garden. Am I to assume adjacent in this sense means directly opposite, and that my patio would be classed as being adjacent?
Pic for reference:
Any ideas on what to search for to dig up that thread with the planning consultant?
Edited by rinseout on Monday 11th August 14:27
On the other hand, it’s only an issue if the local planning have it reported so there’s a risk assessment to be done there…………
This is Equus website. https://www.sensusarchitecture.co.uk/
I have worked with him professionally he was good, he knows his stuff but his bedside manner isn’t for everyone….
I have worked with him professionally he was good, he knows his stuff but his bedside manner isn’t for everyone….
Many thanks. I had a long chat with Equus. Great guy.
1. Something that's still confusing me is the 30m2 rule. I'm sure it comes under permitted development, but Equus and someone at the top of the thread stated that it was under building regs. Is it because it's over 15m2?
2. So a building regs approved document only covers masonry buildings up to 3m in height. A timber frame building needs building control, who will ask for calculations. A structural engineer will need to provide the calcs. A pre built shed *may* have calculations already done by the manufacturer.
3. Equus also mentioned that to comply with building regs, the outside as well as inside has to be fire proofed. The inside only requires 15mm plasterboard. The outside is the kicker. He recommended something like magply. I'm looking at £1000-1500 to clad the whole lot. Could I get away with doing the internal and 2 external sides closest to the boundary?
4. It's probably wise to stay on the safe side and assume the highest point is measured from the garden itself, rather than including the patio. This still gives me something like 650mm extra height.
My neighbours shed is right next to my shed with a fence in between and it comes up to around 3m if measuring from my side. Would his garden be classed as 'adjacent'?
All this for a shed that's well away from a dwelling. Ridiculous.
If I were to go ahead and build this without complying with building regs, what's the worst that could happen if they were to find out? My neighbours aren't likely to complain as it's mostly out of sight, and they're not really the type either.
1. Something that's still confusing me is the 30m2 rule. I'm sure it comes under permitted development, but Equus and someone at the top of the thread stated that it was under building regs. Is it because it's over 15m2?
2. So a building regs approved document only covers masonry buildings up to 3m in height. A timber frame building needs building control, who will ask for calculations. A structural engineer will need to provide the calcs. A pre built shed *may* have calculations already done by the manufacturer.
3. Equus also mentioned that to comply with building regs, the outside as well as inside has to be fire proofed. The inside only requires 15mm plasterboard. The outside is the kicker. He recommended something like magply. I'm looking at £1000-1500 to clad the whole lot. Could I get away with doing the internal and 2 external sides closest to the boundary?
4. It's probably wise to stay on the safe side and assume the highest point is measured from the garden itself, rather than including the patio. This still gives me something like 650mm extra height.
My neighbours shed is right next to my shed with a fence in between and it comes up to around 3m if measuring from my side. Would his garden be classed as 'adjacent'?
All this for a shed that's well away from a dwelling. Ridiculous.
If I were to go ahead and build this without complying with building regs, what's the worst that could happen if they were to find out? My neighbours aren't likely to complain as it's mostly out of sight, and they're not really the type either.
Edited by rinseout on Tuesday 12th August 16:04
rinseout said:
Many thanks. I had a long chat with Equus. Great guy.
1. Something that's still confusing me is the 30m2 rule. I'm sure it comes under permitted development, but Equus and someone at the top of the thread stated that it was under building regs. Is it because it's over 15m2?
Planning rules vs Building Control rules. Planning doesn't care about the area, only proximity to neighbours and height (for PD). For planning, proximity to neighbours dictates your maximum heights of various aspects of the building.1. Something that's still confusing me is the 30m2 rule. I'm sure it comes under permitted development, but Equus and someone at the top of the thread stated that it was under building regs. Is it because it's over 15m2?
Building Control are only interested in it being built according to the rules. For small detached outbuildings, in summary, these are:
Less than 15m2 of internal floor area, you can build as close to a boundary as you like, no restrictions on materials.
Between 15m2 and 30m2 of internal floor area, at least 1m away from a boundary OR built substantially of non-combustible material.
Over 30m2 of internal floor space, full Buildings Control rules apply (e.g. insulation, foundations, structural signoff, fire safety etc).
rinseout said:
2. So a building regs approved document only covers masonry buildings up to 3m in height. A timber frame building needs building control, who will ask for calculations. A structural engineer will need to provide the calcs. A pre built shed *may* have calculations already done by the manufacturer.
See above, only required if more than 30m2. In which case, someone must do the calculations and have them approved.rinseout said:
3. Equus also mentioned that to comply with building regs, the outside as well as inside has to be fire proofed. The inside only requires 15mm plasterboard. The outside is the kicker. He recommended something like magply. I'm looking at £1000-1500 to clad the whole lot. Could I get away with doing the internal and 2 external sides closest to the boundary?
It depends, you will need to justify the non-combustible nature of the whole structure, if that's the element of concern to you. In likelihood, it won't.rinseout said:
4. It's probably wise to stay on the safe side and assume the highest point is measured from the garden itself, rather than including the patio. This still gives me something like 650mm extra height.
The datum point for the levels you can work to are extremely well defined (pre-existing level adjacent to the building). If you start exercising interpretations of this, it will be very easy for a Planning Officer to contest your build. The threads I linked to had someone who fell foul of exactly that situation - debate over original ground height datum.650mm is a lot if that's the height differential of the slope where it is covered by the footprint of your building. Are you sure - that's a heck of a slope, if so you are relatively laughing (similar situation to mine). Can you upload a photo of the site or sketch of a plan of the site levels with some rough measurements? We can probably give you a plan of attack to get this done completely under PD and gain any available height benefits from levelling the plot.
rinseout said:
My neighbours shed is right next to my shed with a fence in between and it comes up to around 3m if measuring from my side. Would his garden be classed as 'adjacent'?
Adjacent to your garden, absolutely. Adjacent to your building, depends where you build it in relation to his.rinseout said:
All this for a shed that's well away from a dwelling. Ridiculous.
Them's the rules, if you want to do it under PD, need to comply. They're actually quite accomodating, but the closer you get to a boundary the more restrictive they are to avoid overbearing your neighbour.rinseout said:
If I were to go ahead and build this without complying with building regs, what's the worst that could happen if they were to find out? My neighbours aren't likely to complain as it's mostly out of sight, and they're not really the type either.
If not compliant with either PD or Building Control and someone finds out then you would be given a notice to comply by modifying the details that don't comply. If it's the PD elements you breach then you can put in for retrospective full Planning Permission, which if granted would let it stand. Building Control rules need to be complied with. If you don't resolve the order to make the building compliant, then you can be forced to pull it down.Equus's advice when on these forums was always to design what you want, then if it isn't covered by PD then go for full planning. Life's a bit more nuanced than that , but it's a good starting point. If it's only slightly outside of PD then the Planning Permission decision ought to take into account the quantum by which your design exceeds what PD permits ie a small height increase beyond PD shouldn't stress them too much.
Building Control rules - if they apply, you need to comply. No leeway or alternative plan there.
For more insightful advice you really need to give us some concrete information on what you want:
- site levels where the building would go (all other levels are immaterial)
- proximity to boundary
- floor area
- eaves height, max roof height of your design.
Edited by PhilboSE on Tuesday 12th August 16:57
rinseout said:
I'm quite sure my neighbours would be ok with it.
The issue with this is if you come to sell the property, the future buyer's solicitors are very likely to ask you to prove it was PD or full PP and complied with relevant building regulations. If you can't do this, they'll make a meal of it and ask you to buy an indemnity policy and/or tell the buyers to attach no value to the building.Also, anyone can raise a planning breach, not just your neighbours. Planning departments have very detailed data these days, their online site plans contain very detailed building and outbuilding outlines even if they were never officially told about them. So any structures you build are more visible than you might think.
Some clarifications, since you're referring to our conversation:
'Permitted Development' is a term used to mean that it doesn't need PLANNING approval.
BUILDING REGULATIONS uses the term 'exemption' rather than 'permitted development'.
Under 15m2 floor area is exempt Building Regulations, full stop.
Between 15m2 and 30m2 is exempt Building Regulations UNLESS it's within 1m of the boundary AND it's not made of 'substantially non-combustible materials.
For a building of the size you're considering (24m2), you therefore have 4 options:
1) Apply for Building Regulations approval - which for various reasons is likely to make it MUCH more expensive.
2) Relocate the building more than 1m. from the boundary.
3) Build it from 'substantially non-combustible' materials (which effectively means masonry, in this case).
4) Carry on regardless and hope for the best (which professionally, I couldn't possibly encourage).
None of this has any relevance to Planning.
For what it's worth, Planning actually allows any floor area up to 50% of the original curtilage (garden) area, provided the use is 'incidental to the enjoyment of the dwellinghouse' (though the 'incidental' bit means that its use needs to be reasonably subordinate in scale to the use of the dwellinghouse). Other than that, the size limits for Planning relate to height, not floor area.
And some 'old school' Building Control Officers might be willing to exercise common-sense judgement and let you get away without submitting calcs on a timber frame or SIPs structure, on the basis that they can judge from experience and intuition whether it's likely to be strong enough, but post-Grenfell they're becoming fewer in number. Most will (understandably) want to do it by the book.
1) Structural fire resistance: main aim of which is to ensure that the building stays standing long enough for it to be evacuated (the Regs say nominally 30 minutes).
2) External surface spread of flame: main aim of which is to stop the fire spreading to neighbouring properties.
Some Building Control Inspectors (again, increasingly fewer in number) might take a relaxed view about (1), because a building of this size can be evacuated in 30 seconds, never mind 30 minutes, so they might not insist on the fire-resisting (Magply) external sheathing of the loadbearing timber structure... if the fire comes from outside, burning in, then it really doesn't matter how long the building stands, so long as it is long enough to get the people out? The actual Building Regulation (rather than the approved document) says only that: 'The building shall be designed and constructed so that, in the event of fire, its stability will be maintained for a reasonable period'.
Others will take the view that the Approved Document says that the 'reasonable period' is 30 minutes, so 30 minutes it is; and in any case, if the building prematurely collapses into a big bonfire before the fire brigade has chance to get there, then that will contribute to the risk of it spreading to neighbouring properties.
Sheathing only part of the timber frame won't help in either case: you'd only be ensuring stability of part of the structure.
IN ADDITION to sheathing the loadbearing timber/SIPs structure in something fire-resistant to ensure structural integrity, you will also need the external cladding to be something resistant to surface spread of flame, like Cedral/HardiePlank or (certified) factory fire-retardant treated timber, to protect against external transmission of the fire.
There are other issues that you need to deal with as soon as Building Regulations is triggered for a timber frame - proper insulation and moisture control for two - but bottom line is that you probably don't want to go there: Building Regulation compliance will be expensive.
As above: the easy answer for your particular building is simply to locate it at least 1m. from the boundary (or 2m. if you want the height allowance under Planning to go up to 4m., if you use a dual pitch roof) and all your problems go away... you can then build the damned thing from sticks of gelignite, for all the Building Regulations would care.
Otherwise, you're unfortunate that the size of building you're proposing, in the position you're proposing, just happens to be the wrong side of the line that the legislation draws.
rinseout said:
1. Something that's still confusing me is the 30m2 rule. I'm sure it comes under permitted development, but Equus and someone at the top of the thread stated that it was under building regs. Is it because it's over 15m2?
As we discussed (and as roscopervis has said further up this thread) Planning and Building Regulations are entirely separate systems, working to different rules, and administered by different teams within the Local Authority. Don't confuse or conflate the two: Planning deals with external appearance and the potential impact of the building or use on other people. Building Regulations deals with the technical construction standards of the building, to make sure that it's reasonably safe, durable and energy-efficient.'Permitted Development' is a term used to mean that it doesn't need PLANNING approval.
BUILDING REGULATIONS uses the term 'exemption' rather than 'permitted development'.
Under 15m2 floor area is exempt Building Regulations, full stop.
Between 15m2 and 30m2 is exempt Building Regulations UNLESS it's within 1m of the boundary AND it's not made of 'substantially non-combustible materials.
For a building of the size you're considering (24m2), you therefore have 4 options:
1) Apply for Building Regulations approval - which for various reasons is likely to make it MUCH more expensive.
2) Relocate the building more than 1m. from the boundary.
3) Build it from 'substantially non-combustible' materials (which effectively means masonry, in this case).
4) Carry on regardless and hope for the best (which professionally, I couldn't possibly encourage).
None of this has any relevance to Planning.
For what it's worth, Planning actually allows any floor area up to 50% of the original curtilage (garden) area, provided the use is 'incidental to the enjoyment of the dwellinghouse' (though the 'incidental' bit means that its use needs to be reasonably subordinate in scale to the use of the dwellinghouse). Other than that, the size limits for Planning relate to height, not floor area.
rinseout said:
2. So a building regs approved document only covers masonry buildings up to 3m STOREYS in height. A timber frame building needs building control, who will PROBABLY ask for calculations. A structural engineer will need to provide the calcs. A pre built shed *may* have calculations already done by the manufacturer.
Edited for accuracy.And some 'old school' Building Control Officers might be willing to exercise common-sense judgement and let you get away without submitting calcs on a timber frame or SIPs structure, on the basis that they can judge from experience and intuition whether it's likely to be strong enough, but post-Grenfell they're becoming fewer in number. Most will (understandably) want to do it by the book.
rinseout said:
3. Equus also mentioned that to comply with building regs, the outside as well as inside has to be fire proofed. The inside only requires 15mm plasterboard. The outside is the kicker. He recommended something like magply. I'm looking at £1000-1500 to clad the whole lot. Could I get away with doing the internal and 2 external sides closest to the boundary?
I should stress once again that there are two separate issues at play, here:1) Structural fire resistance: main aim of which is to ensure that the building stays standing long enough for it to be evacuated (the Regs say nominally 30 minutes).
2) External surface spread of flame: main aim of which is to stop the fire spreading to neighbouring properties.
Some Building Control Inspectors (again, increasingly fewer in number) might take a relaxed view about (1), because a building of this size can be evacuated in 30 seconds, never mind 30 minutes, so they might not insist on the fire-resisting (Magply) external sheathing of the loadbearing timber structure... if the fire comes from outside, burning in, then it really doesn't matter how long the building stands, so long as it is long enough to get the people out? The actual Building Regulation (rather than the approved document) says only that: 'The building shall be designed and constructed so that, in the event of fire, its stability will be maintained for a reasonable period'.
Others will take the view that the Approved Document says that the 'reasonable period' is 30 minutes, so 30 minutes it is; and in any case, if the building prematurely collapses into a big bonfire before the fire brigade has chance to get there, then that will contribute to the risk of it spreading to neighbouring properties.
Sheathing only part of the timber frame won't help in either case: you'd only be ensuring stability of part of the structure.
IN ADDITION to sheathing the loadbearing timber/SIPs structure in something fire-resistant to ensure structural integrity, you will also need the external cladding to be something resistant to surface spread of flame, like Cedral/HardiePlank or (certified) factory fire-retardant treated timber, to protect against external transmission of the fire.
There are other issues that you need to deal with as soon as Building Regulations is triggered for a timber frame - proper insulation and moisture control for two - but bottom line is that you probably don't want to go there: Building Regulation compliance will be expensive.
rinseout said:
All this for a shed that's well away from a dwelling. Ridiculous.
Both the Planning rules on Permitted Development and the Building Regulations Exemption criteria are fairly blunt tools, intended to deal with the generality of most, typical situations: they're not perfect and can create all sorts of anomalies, but they have to draw the line somewhere.As above: the easy answer for your particular building is simply to locate it at least 1m. from the boundary (or 2m. if you want the height allowance under Planning to go up to 4m., if you use a dual pitch roof) and all your problems go away... you can then build the damned thing from sticks of gelignite, for all the Building Regulations would care.
Otherwise, you're unfortunate that the size of building you're proposing, in the position you're proposing, just happens to be the wrong side of the line that the legislation draws.
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