Timber frame mancave construction advice

I’ve out grown my current shed,its packed to the rafters so thought i’d have a go at building one. I want to be able to use it as office so needs to be nice and warm in the winter.
If a had a big sack of cash lying around I’d just get someone in and build something like This but time to see if me woodwork skills have progressed since the mighty key holder I made in DT 20+ years ago,
Got to stay under planning rules so limited to a 5m x 3m building and 2.5m total height. my gardens not that big so couldn’t go much bigger even with planning.
Going to have to a be a flat roof and a warm flat roof construction seems to be recommended. However iam not keen on the deep fascias this creates with a decent amount of insulation. Found a company that would do me a good deal on some tapered insulation which would go from 140mm thick to 90mm creating the falls, I would then whack a epdm membrane over the top.
To avoid the deep fascia, rather put the joists on top of the wall plate would I able to put the joists running in between the two walls so the the top of the joists come level with the wall plate for my osb deck to screw into.
Would this be a bad idea structurally?
Floor and roof is going to be 6×2 timbers at 400mm centres
Walls 4×2 at 400mm centres
Thanks

What sort of money are you going to throw at this?

£3500 ish I suppose depends what I can get on eBay and what I clad the exterior in.

I would head down the good quality big shed / cabin and whack some insulation lining in route.

Buy a second portable site office 🙂

You can always on in the future.

I bought one for £650 with delivery. It had lighting, heating, telephone and as bonus desk & chair. And security grills on the windows and doors.

PS It is 12ft x 8ft

http://compare.ebay.co.uk/like/140901081201?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar&cbt=y

or

http://www.shippingcontainersuk.com/m9b4s14p206/SITE-OFFICES-South-Wales-Steel-Office/RS_GB

Like this
http://www.elbecgardenbuildings.co.uk/Log-Cabins/Shire-Bradenham-Log-Cabin

Forgot to mention access to garden is terrible, through the house or down a narrow ally. Definitely going down the self build route as I just fancy having a go at it.

At 5m make sure you go up to 6×3 or maybe 8″ as trust me – they will sag

Talk to Warwick Buildings in Southam – at tht price they will build you what you want in sections that you just screw together.

Joists were going to run across the 3meter span so figured 6″ would just about alright at 400mm centres no real snow loading to worry about in London.
All the pre made sheds seen to framed with 2×2 or at most 3×2 so thought I could get a more substantial structure for the same money. Thicker timbers also allows for more insulation to bd crammed in. Can’t find the bit of paper with qoute I got for all the timber apart from the cladding and it came in at around £1800 I think.
I’ll give that company a call see what they say

THIS is how I imagine it will look(yeah right) though I don’t really like that vertical cedar cladding, luckily cause its really expensive. I found some reasonably price English red cedar feather edge I really like so will proberly go with that

For 3500 quid, I reckon you could build it bricks or concrete blocks n render? There are companies that do 2nd hand king span and the likes as well, save a shed load with that.

http://www.secondsandcoscotland.co.uk/

And tapered stuff – http://www.secureviewer.co/SecondsandCo/viewcategory.php?groupid=18

Don’t understand the problem at the fascia or the need for over insulating the roof construction.

My understanding of the warm roof construction was that the joists sit on the wall plate then a osb deck then your kingspan with osb on top then your epdm. So your fascia would the roof joist 150mm + 140mm insulation plus 30ishmm of osb. i was thinking a 320mm fascia would look a bit odd hence my idea for putting joists between walls rather than on top

Save a shed load- lol!

Depend on how you finish the joists. If you want to extend them across the wall then your construction depth will be large as you pointed out.

If you want an overhanging fasica then come up with a detail to reduce the thickness at this point. I would also avoid tapering and look at a bonded ply route. EDPM is very thin so prone to “ghosting”.

At a 2.5m limit I would also take a look at your build proposal. 2.5m minus 140mm / ply / joists / ceiling / lights = low head height.

Not heard of ghosting, whats that?
I realise its not going to have the best of head room but i’am only 5ft10 so not to much of a issue, I hope.
Think I’ve got my calc’s right
150mm floor joist
18mm ply
2000 walls
150mm joists
18mm ply
90-140mm king span
9mm ply
= 2467mm
I’d leave the joists open, so I could use some for storage

Ghosting is when the sunstrate reflects through the membrane. As the EDPM is so thin its more prone to “showing” fixings / joints and general damage to the substrate below. Insulation, as a substrate, is more prone to damage.

I would maximise the head height.

Might be worth having a chat with a SIPS company to see if you can buy any roof cassettes at a good price.

How big is your garden? 2.5m is the max height allowed within 2m of the boundry. Otherwise Max height can be 4m ( dual pitched roof, 3m for a single pitch ) but no higher than 2.5m at the eaves

A 3m or 4m roof height will give you a lot more headroom, will be a lot cheaper to construct and easier to weatherproof. At a guess a flat roof will be twice the cost of a pitched roof and built by someone with more than basic DIY skills. Dont underestimate the weight of snow even if you are in london it would be a shame if after it’s built London gets the brunt of the bad weather the following year. Use a construction grade timber for the roof ie. C24 ( dry-graded ).

A hardwood cladding would be best for longevity as would a raised floor allowing the air to flow underneath will prevent rotting.

Ah ok, I wouldn’t want to be looking down on that showing through the epdm.
The other roof option I looked at, similar i suppose to the sips, was the insulated steel panels. They had 80mm of insulation and just needed a single beam running across the 5m span to support them if the fall went down the 3m span.
I liked the idea of just building the walls all the same height and letting the insulation take care of the fall

5.7 meters wide and and I can only come out 3.5meters because of the kids swings.
Might be worth putting planning in just so I can put a proper roof on even if I don’t increase the floor size much

So the distance left and right of said man cave to boundry will be 350mm & 500mm to the rear?

will probs be 350mm all round. the fence panels surrounding can slide out of fence posts during construction to give a bit of working room

I liked the idea of just building the walls all the same height and letting the insulation take care of the fall

Firrings.

will probs be 350mm sides and rear. the fence panels surrounding can slide out of fence posts during construction to give a bit of working room

For your roof, what about 18mm OSB3 deck with Onduline corrugated bitumen sheet on top? It’s what in contemplating for my garage.

Yeah not fixed on the epdm just seemed like a nice easy solution. Also being one piece less likely to leak on such a shallow pitch

Your going to need a minimum pitch with onduline and have to have it overhanging other wise the rain will get in under the corregations. You’ll also have to come up with something to stop the rain running along the underside of the corregations. Onduline + dual pitch = good, Single pitch = Bad.

Just started a planning application, it’s made my brain hurt 🙄

other wise the rain will get in under the corregations. You’ll also have to come up with something to stop the rain running along the underside of the corregations.

Please explain how this occurs in a little more detail.

Capillary water run back

My two penneth worth. If single pitch create the slope in a pent style by literally making the front elevation higher than the back . Roof build up at fascia level will not be a problem as surely you will keep it in plane with the walls and therefore clad over the timbers exactly the same?
If going for a dual pitch think in the same manner as a small shed and place the door in the centre of the gable, this will give you the head height but will obviously reduce as you move towards the eaves. In sheds these areas are usually racked out or shelved therefore keeping you away from the low head height.

I bet you wish you hadn’t asked!

You’re building a shed, not The Shard. It’ll be 10ft wide. 6×2 joists @ 400mm c/s will be fine and,in answer to your original question, can either sit on top of the wall frames (cut flush and clad over) or bolted within the wall frame. You could use joist hangers but these may cause a cold bridge. You could cut the insulation to finish flush with the wall frame and clad over then run the deck board and membrane beyond the cladding. Be sure to fold the membrane around and under a drip batten and fit a facia to carry a gutter. If the door is on the ‘low side’, ensure you have enough height to allow it to open (if opening outwards) to clear the facia/gutter! Plus, make sure you have enough room for a water butt 8)

EDIT: wrightyson beat me to it!

At a 2.5m limit I would also take a look at your build proposal. 2.5m minus 140mm / ply / joists / ceiling / lights = low head height.

Or dig down…, obviously depends on the water table – but dig a test hole and find out.

pitch roof? think you’re then limited to 2.0m at the eaves,max height 4.0m

I bought a cedar workshop from Kent Sectional buildings for less than that! It comes in panels that would fit down your alley, and assemble in a tight space, as they bolt screw together on the inside.

Cedar is much more resistant to rot and insects than pine.

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Watching this with interest….

I’ve just knocked up a beautiful 3m x 1.2m with a dog leg to 0.9m (strange size I know) bike store/logstore/tumble dryer housing for about 300 quid. All in tanalised with good quality 12mm tongue and groove and slate roof for less than 300 quid. Admittedly slates were off an old job. Timber isn’t a “cheap” option anymore but it’s so much more forgiving on the diy’er (with all respect) than blocks/bricks etc

we built a 3.6 w x 3.2 x 2.4 h garden office out of 4×2 and 4″ kingspan (roof walls and floor) last year and the materials came to £2000. The walls were 12mm ply with a breathable membrane. 6×2 roof with 18mm decking ply and green mineral felt. They hadn’t decided on an exterior cladding and still haven’t