Advice needed for workshop/garden-office project

[haf63]

I recently came across this site and its amazing. I have read through a number of projects as part of my research and feel i have a good grasp of the fundamentals so hopefully won't ask too many 'basic' questions.
I am fairly familiar with building/planning as have done both a small extension and project managed a large one so understand most of the trades and regulations.

The attached file shows a top view on the left showing the shed within 1m of the fence and an irregular shape.
On the right top you can see a side view showing single slope roof
On the right bottom an example of what i think is the right solution for me

So my thinking so far
- I don't think i need planning as its less than 30m and max height is 2.5m
- I don't think I need building regs but will need an electrical cert
- I am unsure on brick or block render or wood but leaning towards wood
- I think i 2 options on fire safe cladding so cement board or composite but not sure which is better or costs delta's
- I will have to go with a flat roof design to maximise space given 2.5m limit - but not sure exactly what kind of flat roof yet.

Any comments/advice appreciated as I am a the early stage so can change pretty much anything
Budget is a concern but don't have a max figure - ideally 5k but can go a bit higher
I will be doing pretty much everything myself or with a few friends in the building trade

 

[porker]

I think your assumptions are about right on the PP and Building Regs. There are exceptions of course (such as AONB etc.) so I would check with the Planning Portal and your local council resources to check you comply. The electrics will come under Part P so you will need to consider that. Having built a workshop that required PP and building regs and a home office previously that did not, I would say the PP wasn't that onerous and it got me what I wanted. For the combustible material issue, Steve Maskery went through this so worth seeing his workshop build if you haven't already.

I would say you could get what you want for your budget depending on the fit and finish you choose. I'm currently looking at a similar home office to your design in my garden and am looking at a concrete block consruction with a timber cladding. Having just installed a bi-fold door in my house, it is worth looking for misfit doors etc. which can be picked up very reasonably for the front. I am considering an EPDM roof as I have used before with good results. For the base I would consider a base that doesn't allow rodents to move in underneath. There are several options for this. I prefer concrete bases but can be a lot of work.

 

[haf63]

Thanks porker,
The workshop as described size/roof/etc is pretty much what i want so i don' think there is a need for PP but agree that its not difficult shpould i need it.
I like EPDM idea as its long life so will explore that option versus traditional felt.
I have done a few concrete bases so see that as a straight forward floor option
I keep flipping between bricks/blocks/render/cladding and I have a brickie mate so it will be easy-ish to get that done. What is your reason versus traditional wood/cladding as I am struggling with one over the other - is it cost/insulation/etc that swings it in one directon. Aside from bricks taking more space than wood.

 

[porker]

TBH - I don't have any real strong preference. It's rather I am more familiar with building with blocks, mortar and plastering etc. I built a home office previously from wood. It was a kit though so all the thinking had been done for me. The end result was great and fully insulated. Plenty on here have built in timber with great results. Having priced it, there is probably not much in it regarding materials but the blocks option would take longer.

One thing I learnt was it is well worth insulating the floor whatever you do. I left this part out initially and retrofitted later. It was a pain but worth it.

 

[MikeG.]

.......So my thinking so far
- I don't think i need planning as its less than 30m and max height is

The 30 sq m rule is nothing to do with Planning. It is the maximum size you can build without Building Regs approval.

 

[MikeG.]

TBH - I don't have any real strong preference. It's rather I am more familiar with building with blocks, mortar and plastering etc. I built a home office previously from wood. It was a kit though so all the thinking had been done for me. The end result was great and fully insulated. Plenty on here have built in timber with great results. Having priced it, there is probably not much in it regarding materials but the blocks option would take longer. ..........

The principle difference is that blockwork walls will end up much thicker, so for the same size floor area you would need a bigger footprint and roof. With a timber construction the insulation falls within the thickness of the structure, but with blockwork you will need to add it to one side or the other........and then protect it. There aren't many circumstances in which I could understand why anyone would choose blockwork.

 

[haf63]

Thanks MikeG and my mistake on the 30m planning/building-regs comment. Main thing is I don't need either.
I am firming up on the floor being concrete slab and will be following Mikes process on that.
I am also leaning towards wood frame thats insulated so again as per Mikes process - and also investigate fire resistant cladding. I read another post which suggested having cheaper cement boards on the 2 non-visible fence sides and decent cladding on the 2 visible sides so that may be a good cost saving meaure.
Roof options are being narrowed with warm roof EPDM looking most likely
I will also start looking at what bi-fold doors etc appear on ebay and other places to see what i would pay for a 2-3m run
Hopefully i can tie down design and materials to get a more accurate cost and then start to do the work once lockdown eases as at the very least I need a skip

 

[Sheptonphil]

My current build needed planning permission, not because of its size, but its location and materials used for aesthetics. Don't just assume you don't need planning. Its not better to ask for forgiveness than permission in these cases. Get the planning office on your side in case you do need it, same with building regs.

Building regs is also a lot more than just dimensions, its even more about proximity to boundaries, intended use, and the implications of that in terms of build methods and materials used.

 

[MikeG.]

My current build needed planning permission, not because of its size, but its location and materials used for aesthetics........

I know what you mean, but the way you've said it could be a little misleading. No building allowed by Permitted Development then requires Planning Permission because of its proposed materials. In other words, if your building is allowable under PDR then it doesn't matter what it is made of other than for Building Regs reasons (not Planning reasons).

 

[RobinBHM]

I just thought Id mention, between 15 and 30 sq metres building closer than 1 metre must be of non combustable material to maintain a fire break between boundaries. I know your post talks about fire proof cladding, so I guess you know this.

What I dont know is what building regs considers non combustible - although this is discussed in Steve Maskerys mammoth thread on this forum.

I built my garden office with combined shed using 4 x 2 studwork, 50mm celetex in between, then clad externally with 18mm OSB, then another 50mm celetex, 25mm battens, Siberian larch cladding.

Nb Im not necessarily recommending this construction as it isnt a recommended detail, but I chose it as it allows a continuous 50mm celetex externally with no thermal bridging.

The 50mm between the studwork left about 45mm gap for running electrics -which were run in the roof, then dropped down complying with the safe zone rules.

I built a warm roof with 120mm ceoetex, OSB and EPDM.

If you dont care what the back and side of your structure looks like, maybe you could clad with rendaboard and paint it. Then clad the other 2 walls in marley eternit. Rendaboard is cheaper than eternit and its non combustible. I dont know it meets suitable fire rating.

 

[Sheptonphil]

There was some 'disussion' between my Building Control Department about the need for full regs even though I met the criteria of less than 1m, predominantly non-combustible and less than 30 sq metres internally because it was attached to the house.

The notification came in that I was liable for full building regs at £565

see cut and paste from my email:-

Good morning,

Thank you for your e-mail.

The submission fee for this application is £565. This can be paid via one of the following:

• By calling 0300 303 7790 to make a card payment quoting reference 2/BN/*******/***
• By BACS to sort code: 60 03 27, account number: 7914 1684, account name: Sedgemoor District Council

Once the payment has been received the application will be validated and you will receive confirmation of this via e-mail.

We then need 48 hours’ notice before works commence.

We will inspect the different stages via video call or photographs depending on what the surveyor needs to see.

Once the evidence has been received they will then confirm you are ok to continue to the next step.

Kind regards

*/****nne

***********d Tech CABE
Business Support Assistant
Somerset Building Control Partnership

Bridgwater House
King Square
Bridgwater
Somerset
TA6 3AR

Direct Tel No: 01278 435***
E-mail: ***************@sedgemoor.gov.uk

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Tel: 0300 303 7790
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Click here for the SBCP Webpage



A joint service between Mendip District Council, Sedgemoor District Council and Somerset West and Taunton Council.





From: Phil Stevens <*********a.net>
Sent: 30 March 2020 17:06
To: ***************d <************[email protected]>
Subject: RE: [OFFICIAL] - *************** G***r

Good afternoon R********

I have answered the questions in the order asked

1) The internal size is a fraction under 29 sq metres
2) The distance from boundary is 0.4m from but 20 metres from neighbouring house. It will be attached to our house, but with no connecting entrance in to our house, the only entrance will be from our garden.
3) The construction will be predominantly non-combustible, with British Gypsum Fireline plasterboard internally, walls filled with rockwool insulation which is fireproof and Hardie plank cement fibre cladding which is also fireproof. The roof will be Marley cement slates, again fireproof. All these materials have BS certification for fire resistance
4) There will be no sleeping accommodation, and no heating or plumbing. There will be electrics, being designed, installed, tested and certified by Tony Jones Electrical, a fully qualified electrician.



After much communication back and forth it was agreed I did not need them! but she was having none of it for several days arguing, and kept calling it a garage.

******** to protect personal details of both parties

 

[Sheptonphil]

My current build needed planning permission, not because of its size, but its location and materials used for aesthetics........

I know what you mean, but the way you've said it could be a little misleading. No building allowed by Permitted Development then requires Planning Permission because of its proposed materials. In other words, if your building is allowable under PDR then it doesn't matter what it is made of other than for Building Regs reasons (not Planning reasons).

Sorry, yes, in my case I have no permitted development, and that meant planning permission, which then insisted on the aesthetics of the finishes, eg the roofing had to be tiled to match house. You cannot assume you have permitted development rights, as ours was removed when the estate was built on Duchy land.

Building control were a law unto themselves, insisting I needed full regs compliance.

 

[haf63]

I have been talking to a mate of mine as it turns out he did something similar in terms of a garden workshop-office. He was on a tight budget so did the following for the walls (the bit i'm interested in)
- built 4 brick pillars for each corner
- filled in with single line concrete blocks - done in 1 day by a brickie for a couple of hundred pounds
- dot and dab attached 50mm insulated plasterboard
- taped and painted directly on plasterboard
- used dot/dab gap to run wires
- roughly rendered the 2 external sides with cement/paint
- used plastic cladding on battens on the 2 visible sides
- used ebay french doors and odd size windows

This sounds very appealing and I haven't really seen this approach in my reserach so was wondering if I am missing major downsides?
I would stay concrete slab floor and strip foundation plus epdm flatroof - plus go up a notch in quality- but the principle of the walls seems sounds

Comments wellcome

 

[MikeG.]

Go down that route and you need a foundation. That's a 1 metre deep trench all round, minimum. You also have a wall prone to interstitial condensation. I simply don't understand the fixation that people have with masonry.

 

[haf63]

masonary fixation aside, shouldn't those little vents that brickies put in place of the odd cement line help with any condensation within the structure - though I doubt I know what I am talking about in this area.

 

[MikeG.]

No, because there is no void for the air to move around across the inside face of the brickwork.

 

[haf63]

What about the 1 inch or so gap created by dot+dab between inner face of brick and insulation? Sorry for dumb questions but just trying to understand as its important..

 

[haf63]

Also forgot to ad that the insulated plasterboards are foil backed so have a vapour barrier built-in