What kind of outbuilding/extension would work here ?

[tmasa]

Need a (partly) insulated room as an extension at the back of a link-attached single garage.
The area is currently covered with not very even garden tiles (ants and old hedge roots are to blame).
No building DIY skills.

Does not have to be same temperature as the house, just protected from the elements, dry and having 10+ degrees without spending a fortune on heating.

The purpose: home gym (squat rack/bench/barbell) / tumble dryer (needs 6+ degrees) or laundry sorting/drying area with added dehumidifier / dry storage for things that might get mouldy in sheds.

Ideally lower budget as we are not sure that we will be staying in this house long term.

Not sure about raised manhole (~5 inches high) - assume it is possible to make it lower, don't really want to move it, OK to have floor access cover inside the room.
And also about regulations for the distance from the neighbour's fence, not much information in the internet for link-detached houses.

Options:

- I really like the addroom idea from dunster house, but they don't have this size/configuration or even close that could be modified - where depth would be higher than width and windows/door in the right places. - less than £10K + assembly.

- conservatory - known temperature issues would probably be fine here, but all glass does not sound like a good combination with free gym weights and also need solid walls for storage. And there also won't be any ready made in this configuration. Costs are similar to addroom (?).

- proper brick extension - can be built in bespoke configuration, but is overkill for my needs given the costs ~3K per sqm = ~30K+ ?

- some kind of garden room or shed with modifications to allow access though the garage door and to wrap around the corner (or give up on that extra space 1mx3m and keep it as 2.5x5m rectangle) , is it feasible ? Costs for an insulated one will probably be similar or higher than addroom.

- just give up and get a standard addroom added at the back of dining room. That area will be hard to access and wasted due to it being surrounded on all sides and will make garden layout awkward. No good place for a garden room elsewhere and need to have it accessible from the house.

What approach makes sense here? Thanks

 

[Deluks]

If you might be moving in the future, would you wish to take this shed with you? (At the end of the day it is just that)

Making something modular, held together with bolts rather than nails means you could potentially take it with you.

For your budget/non permanent requirements, then a timber frame made up in sections would be easiest.
If you make a base frame from treated 6x2, then you only need rake over the site and cover with membrane, sit the structure on concrete blocks on well tamped soil.
4x2 stud walls, bolted down to the base and to each other. Make them the width of a sheet of 11mm OSB, for ease of erection and future transportation.
Get a second hand door and double glazed window. FB marketplace/ebay or ask local D/G firms for mismeasures.

Once you've got that up you can think about cladding, roof covering and internal insulation.

 

[tmasa]

Thanks, would I need a planning permission for something like this given it is next to the neighbour's fence (few inches gap) if keeping below 2.5m height? Not planning to remove if moving

 

[Deluks]

Keep it under 15m² and under 2.5m and you've no worries.
A few inches from the fence might irk the neighbour if a) it's their fence and they can't maintain it. b) rainwater runs off the roof onto their side or into the fence.
Slope the roof away or fit a gutter in that side, that doesn't overhang the fence.

It's worth leaving more than a few inches gap for ventilation. Future maintenance for you will be an issue, maybe consider using plastic or metal cladding on the back wall, even if just beneath the fence.

 

[tmasa]

Also, if going contractor route, should I be considering SIP panels or the job would be too small to find anyone willing to take it ?

 

[Deluks]

A half decent builder/jobbing chippie would be ok working with SIPs, it's not exactly rocket science.
Lots of companies online that can supply SIP panels, so it's eminently doable as a DIY option.

I found this, which might inspire...

 

[big-all]

go for a bit more insulation than you think you can get away with
if you think you need if you think you need say 50mm rather than scrimp and go for say 30mm go for 70 the heat loss will be far far less if your aiming for plus 10degrees it will be expensive to heat
iff you go for average 10 degrees over say a 3 day cycle from plus 4 to plus 15 then heat from muscle and breathing will help immensely although you may need more ventilation to stop condensation
i have recently been carrying out experiments
well insulated shed [3 inch loft insulation ]95% plus air tight
now i am a 71 year old a bit sendantry lifestyle fat bugger lol
a 670w fan heater [2kw on low] will raise the temperature from say 5degrees at the same as outside to perhaps 12 degrees in 75 mins i now turn off the fan heater and the temperature will settle perhaps 11 degrees
if i go in for dinner i come back out 40 mins later its dropped to perhaps 10.2 now over the next hour it will pull back to say 10.7 so my body heat and a 20w tv adding to heat
now iff you weight lifting or exercising quite intensely would expect you would be giving out perhaps 500-800w
all the glass is eather recyled dg or 9mm twin walled pollycarbonate as a second layer
the shed is wood 10x12ft average 7ft tall [apex roof]
the floor is not insulated but made from 18mm ply topped with 10mm rubber tiles