Garden Room budget estimate

[daiking]

As if I didn't have enough part started and not even started stuff to do, I've been asked to work out what a garden room would cost. I said £10k, I wasn't believed so I've made up an estimate for something I don't know how to do and taken my best stab at it.

 

It would be a trapezium (?) shaped building due to the shape of the bottom of the garden, surrounded by trees and about 5m from a stream. It would be 1m from the boundary one each side. It would be approximately 27m2, constructed like a glorified shed and must not be taller than 2.5m.

 

What I am looking for is feedback if there is anything wrong or just missing from my costings. 

 

What would different base/foundations cost? I've just proposed this as it is the simplest easiest method to DIY, about 1800mm max between posts. A 100mm concrete slab + ring beam would require  a lot of digging and 3-4m3 of concrete and this spot is 30m from the road through my reasonably clean driveway, patio and garden, not a building site. 

I don't know the details of the joinery and how this will go together without right angled corners but added some extra timber to the estimate. 

Cladding? I have no idea about but would like a modern contemporary vertical straight wooden look. I know proper Larch or Cedar is expensive but there must be something that works out at £25m2 fitted including consumables and accessories.

I have quoted on using EPS insulation throughout as it doesn't need to be great but I wanted to avoid fibre insulation in the floor and lower walls so close to the stream. 

Cold roof could use fibre insulation instead but walls and floor feel I should use EPS. 

The roof, I have no idea how to make work for a 6m front to back span. I'm aware that I might need a steel goalpost arrangement halfway back to split the spans. If so, I'll add another £1k to the estimate.

I've added £50 in 3 sections to cover fasteners, not sure how close this is.

Glazing wise, it doesn't have to be a bi-fold door. An approx. 2m wide french door arrangement with glazed panels either side would be acceptable. I've picked £2k as a round guess.

I haven't included any must have tooling for this: I have a cheap mitre saw and circular saw so any necessary tooling (Nail gun?) will need to be bought/hired.

 

About the only thing missing off this is a stove. I would probably only go for something like a tent stove as it wouldn't need to be big and not get used much. As such, I'll put it as £1k job in the back of my mind for looking at when this plan actually starts moving.

 

shed budget.xlsx

 

£8.1k is the estimate if my spreadsheet makes your eyes bleed. 

 

 

 

 

Edited July 2, 2020 by daiking

[PeterW]

11 posts / pads would be ample with 6x2 framing. Double up all round as beams, make your front using 9x2 doubled as a header and sit  a 4x2 on the top and you’ll have a 1:20 fall across the front to back if you use 6x2 as a back beam. 
 

I would be tempted to keep the structure simple and break it into squares and triangles. Quick fag packet says you have a 4m square that you could build up with 8x2 at 400 centres, just double up the ones making the outside of the square. 
 

Instead of making the whole front open up, why not use slot windows too, and just have the centre 1800 open up ..?? Cheap and easy to do and gives the same light. 
 

Decent 20mm shiplap is about £1.90/m delivered and you will need 9.2linM/sqm so should be easily inside £20/sqm for paneling. If it was me I would be framing the base and fitting battens and filling the gaps with OSB, full fill of 100mm PIR and then use floorboards as the final finish and you’ve no flooring to sort. 

[daiking]

2 hours ago, PeterW said:

11 posts / pads would be ample with 6x2 framing. Double up all round as beams, make your front using 9x2 doubled as a header and sit  a 4x2 on the top and you’ll have a 1:20 fall across the front to back if you use 6x2 as a back beam. 
 

I would be tempted to keep the structure simple and break it into squares and triangles. Quick fag packet says you have a 4m square that you could build up with 8x2 at 400 centres, just double up the ones making the outside of the square. 
 

Instead of making the whole front open up, why not use slot windows too, and just have the centre 1800 open up ..?? Cheap and easy to do and gives the same light. 
 

Decent 20mm shiplap is about £1.90/m delivered and you will need 9.2linM/sqm so should be easily inside £20/sqm for paneling. If it was me I would be framing the base and fitting battens and filling the gaps with OSB, full fill of 100mm PIR and then use floorboards as the final finish and you’ve no flooring to sort. 

 

 

Cheers, I know the base and roof structure need planning properly but I'm just looking for the ball park cost using XXXm of wood, I'll drop posts to 12.  The base I think I understand, I'd probably use PIR in the end but decided to stick with EPS for the first estimate. My wife would much prefer a concrete base but I'm unsure about ground conditions and it would be a lot of work by hand especially if it needed a thicker edge like a ring beam. Would easily eat up any cost saving. We might want tiles as final flooring (would change OSB to ply) so I'm not too concerned about that at the moment - its a known extra. 

 

I think I sort of follow you on the roof, which my interpretation would increase the linear length of 8x2 needed from 100m to about 150m. The base could probably do with the same. I was surprised the about the cost of the EPDM roof but have gone with it. Maybe I should also make the roof 18mm OSB as well, not 11mm. 

 

Cladding I've seen at £15/m2 but I'm leaving it at £20/m2 to cover fixings and accessories like corner posts or whatever.

 

For someone to build a comparable spec unit, we're looking at £1k/m2. Nearly £30k for this by the time you've put in a concrete slab for them as well. 

 

 

[daiking]

Looking at pictures on google, actually I think I've missed ceiling material from my estimate, something to add.

[daiking]

So the professional garden rooms want a slab and then lay timber bearers on it. 
 

If I went down that route, what spec slab would I need? So I can cost it?
 

Better than minimum shed spec 100mm thick 

 

Less than re-inforced ring beam type slab.

 

But what? Compacted hardcore + blinding? How thick? It’s not a house, it’s a timber frame spec shed. Extra depth under walls?

 

There’s a new thread about a garden workshop 25% bigger than this. It’s massively more engineered than my proposal due to masonry walls and green roof but is my outline plan not practical? 

[Declan52]

I have a large shed,18ft*10ft, sitting on 100mm of concrete. No reinforcement at all. I just dug down to the clay and put around 100mm compacted hardcore down then poured my slab. 

How much you need to dig out and replace will depend on your own site. 

I then used 3*3 fence posts around the perimeter and bolted these to the slab. The shed was then built ontop of the posts.

[daiking]

So, following on from my micro office thread, this plan is also dead but will be reborn as a much smaller (12sq m), low spec, off the shelf solution.

 

one thing my wife has requested somewhere for some gym equipment. No serious weights but I think this is pushing me to look at a concrete base for the sub floor.

[PeterW]

Gym equipment takes up a lot of floor space - a 4x3 shed will not take much to be overcrowded with stuff. 

[Big Jimbo]

I think for 30 sq mt you are tight on your budget. Depends what end finish you want. My posh shed at about 25 sq mt will when finished, including flooring, blinds, etc will have cost me 13.5k. this is with all the work being done between me and the Mrs. Like everything, i do think the cost will relate to how much of the work you are willing to undertake, and how much you will need others to do. Where i am in the S.E. i would expect my posh shed to have cost 30k if i had wanted no involvement.

[Ferdinand]

3 hours ago, daiking said:

So, following on from my micro office thread, this plan is also dead but will be reborn as a much smaller (12sq m), low spec, off the shelf solution.

 

one thing my wife has requested somewhere for some gym equipment. No serious weights but I think this is pushing me to look at a concrete base for the sub floor.

 

Is that for storage or use?

 

Have a look at some garage gym type designs, which can cover a lot of different exercises.

 

If you are going to put steppers and walkers in there, the space will soon vanish but things like eg rowers can store on end.

[daiking]

2 hours ago, PeterW said:

Gym equipment takes up a lot of floor space - a 4x3 shed will not take much to be overcrowded with stuff. 

 

Just now, Ferdinand said:

 

Is that for storage or use?

 

Have a look at some garage gym type designs, which can cover a lot of different exercises.

 

If you are going to put steppers and walkers in there, the space will soon vanish but things like eg rowers can store on end.

multi-use space.

 

Just a small bench and a few dumb bells/ weights she said, no machines.

[daiking]

50 minutes ago, Big Jimbo said:

I think for 30 sq mt you are tight on your budget. Depends what end finish you want. My posh shed at about 25 sq mt will when finished, including flooring, blinds, etc will have cost me 13.5k. this is with all the work being done between me and the Mrs. Like everything, i do think the cost will relate to how much of the work you are willing to undertake, and how much you will need others to do. Where i am in the S.E. i would expect my posh shed to have cost 30k if i had wanted no involvement.

That was a first stab, empty shell, no fit out. So would have been up to £12k easily if done - not that it will now!

[daiking]

This has been pointed out to me which is a bit of a come down but looks ok.

 

https://tinyurl.com/y6yy3uy6

[PeterW]

If you’re looking at that sort of thing then have a look at Tuin 

https://www.tuin.co.uk

[daiking]

15 hours ago, PeterW said:

If you’re looking at that sort of thing then have a look at Tuin 

https://www.tuin.co.uk

 

There are some nice cabins there (not sheds). Costs going up ?

[Bitpipe]

Spent quite a bit of time on that site - really like their chatty, open advice on all the requirements and challenges. 

 

Having spent last week in an A-Frame holiday lodge in St Andrews with private hot-tub and sauna, kids now have high expectations of our suggestion for a summer house at the bottom of the garden... 

[daiking]

18 minutes ago, Bitpipe said:

Spent quite a bit of time on that site - really like their chatty, open advice on all the requirements and challenges. 

 

Having spent last week in an A-Frame holiday lodge in St Andrews with private hot-tub and sauna, kids now have high expectations of our suggestion for a summer house at the bottom of the garden... 

The fun police will be along shortly to douse you in bleach

[Bitpipe]

24 minutes ago, daiking said:

The fun police will be along shortly to douse you in bleach

 

Plastic hot tubs with jets etc are normally not my thing but the lodge team were there every morning checking the chemicals and as we left they did a full drain and replenish, filter change etc. My teenager was in it all weathers, even during the howling gale that we had at the start of the week. I was inside watching TV myself.

 

The other half has just seen this though and is very excited https://www.tuin.co.uk/Log-Cabin-Oval-Sauna.html

 

I do fancy one of those Canadian log burning hot tubs https://www.tuin.co.uk/Barrel-Hot-Tub.html

 

And it's all DIYable too. Just need to get my lottery ticket.

[PeterW]

43 minutes ago, Bitpipe said:

 

I do fancy one of those Canadian log burning hot tubs https://www.tuin.co.uk/Barrel-Hot-Tub.html

 

And it's all DIYable too. Just need to get my lottery ticket.

I fancy trying to make something like an Ofuro or Japanese soaking tub but have it wood fired. Not difficult as they are basically a simple lock joint and held together by stainless bands. 

[daiking]

42 minutes ago, PeterW said:

I fancy trying to make something like an Ofuro or Japanese soaking tub but have it wood fired. Not difficult as they are basically a simple lock joint and held together by stainless bands. 

Like a Chinese hot pot 

[oldkettle]

Costco sell barrel saunas https://www.costco.co.uk/Garden-Sheds-Patio/Spas-Saunas/Saunas-Steam/c/cos_9.9.2

Come with heaters, installation optional. 

[PeterW]

They come up on a couple of auction site fairly regularly and go for anywhere between £2800 and £3500 depending on size. They look ok until you realise how tall they are..!

[daiking]

So this permitted development outbuilding rule about height within 2m of boundary

 

Does this just mean that the height of the building within 2m of your fence must be below 2.5m but can be higher 2m+ into your garden or that:

 

If a building is within 2m of your fence at any point, it can’t be taller than 2.5m at all?

 

[Temp]

My understanding is that all parts of the outbuilding within 2m must be below 2.5m but the rest can be higher.

 

It encourages you to put the roof pitch parallel to the boundary rather than a gable end against the boundary.

[daiking]

20 minutes ago, Temp said:

My understanding is that all parts of the outbuilding within 2m must be below 2.5m but the rest can be higher.

 

It encourages you to put the roof pitch parallel to the boundary rather than a gable end against the boundary.

 

That's what I was hoping but I feared I was being deluded to suit my circumstances.

 

My boundaries are not square, meeting at approx 30 degree angle. Therefore while the rear corners of a square building would be within 2m of the boundary, the gable end is many metres away from the rear boundary. 

 

Sounds like I might get away with it.