Another... garage conversion post. Just a sanity check on plans for a detached concrete sectional conversion to a home office

[Danowens24]

Morning all!

I am finally getting round to sorting out our slightly concrete sectional garage conversion - mainly because i'm being evicted from my current home office as my youngest is ready to move in to her own room.

Current state of play:

- 5.5 x 2.5m detached concrete sectional garage (Grimston) - probably dates back to the 70s. Currently 2m from concrete to top of the roof
- Set in to the ground on 2 sides due to living on a hill (approx 1.8m on the back, and sloping from 1.5 to 0m over 4m on one side. The front and opposite side are above ground)
- On concrete base that is relatively flat (slight gradient towards the door which is fine)
- Corugated steel sloping roof on timber beams running widthways and set in to the panels
- 1(single pane, wooden) window and an old wooden (holey) door, 1 up and over wooden garage door
- has electrics and a standalone breaker in the garage, also has water and drainage as it used as a utility room
- Suffers with condensation and leaks

Plans:

- Remove existing steel roof covering and beams
- Add mortar fillet to all existing joints and paint over with bitumen/damp proof paint. Repeat at floor level
- Add visqueen (other brand available) to the floor and run up the wall
- Using lining clips attached through the bolts), attach 3x2 battens at 600mm (panel width) at 2.3m high (increasing overall height)
- Add cross beams at 600s to finish new internal cage/frame and base for roof
- 18mm OSB 3 T&G4 laid on to create new base for roof
- Rubber roof covering installed (a friend is helping with this!)
- Internally adding 50mm PIR insulation between roof beams and 25mm PIR between wall studs
- Laying 50mm PIR on the floor ontop of the DPC/visqueen and 22mm T&G on top to create an insulated floating floor
- Replacing window and door with UPVC equivalents, removing garage door and building new timber frame at the front, covered in OSB and DPC inside and out to ensure the wood remains dry. There will be a new UPVC window installed here and 25mm insulation in the rest of the frame
- cladding externally with shiplap (either timber or UPVC - tbc)
- will either use ply or plasterboard on the wall/ceiling - tbc


Is there anything here that is fundamentally wrong, or anything I should watch out for? It will only be used as my home office, for the washer/drier and some storage for tools (i'll build an internal partition later). The doors and windows will all be vented, and i'll add some leccy panel heaters.

Couple of notes:

- I know this often comes up but I can't tear it down as there's a LOT of land up against it and I dont want to risk any wider damage to the garden / can't afford the cost of a substantial retaining wall right now. I'll do most of the work myself to keep costs down (just need my mates help with laying the EPDM roof)
- the insulation thicknesses came from looking at these fancy wooden office-sheds that i'm looking to copy on the cheap and they are often insulated at 25mm between the internal and external coverings
- I wont be drilling the concrete if I can help it
- the gate will be moving round the corner

I have attached a picture of her in all her dated glory.

 

[noseall]

Morning all!

I am finally getting round to sorting out our slightly concrete sectional garage conversion - mainly because i'm being evicted from my current home office as my youngest is ready to move in to her own room.

Current state of play:

- 5.5 x 2.5m detached concrete sectional garage (Grimston) - probably dates back to the 70s. Currently 2m from concrete to top of the roof
- Set in to the ground on 2 sides due to living on a hill (approx 1.8m on the back, and sloping from 1.5 to 0m over 4m on one side. The front and opposite side are above ground)
- On concrete base that is relatively flat (slight gradient towards the door which is fine)
- Corugated steel sloping roof on timber beams running widthways and set in to the panels
- 1(single pane, wooden) window and an old wooden (holey) door, 1 up and over wooden garage door
- has electrics and a standalone breaker in the garage, also has water and drainage as it used as a utility room
- Suffers with condensation and leaks

Plans:

- Remove existing steel roof covering and beams
- Add mortar fillet to all existing joints and paint over with bitumen/damp proof paint. Repeat at floor level
- Add visqueen (other brand available) to the floor and run up the wall
- Using lining clips attached through the bolts), attach 3x2 battens at 600mm (panel width) at 2.3m high (increasing overall height)
- Add cross beams at 600s to finish new internal cage/frame and base for roof
- 18mm OSB 3 T&G4 laid on to create new base for roof
- Rubber roof covering installed (a friend is helping with this!)
- Internally adding 50mm PIR insulation between roof beams and 25mm PIR between wall studs
- Laying 50mm PIR on the floor ontop of the DPC/visqueen and 22mm T&G on top to create an insulated floating floor
- Replacing window and door with UPVC equivalents, removing garage door and building new timber frame at the front, covered in OSB and DPC inside and out to ensure the wood remains dry. There will be a new UPVC window installed here and 25mm insulation in the rest of the frame
- cladding externally with shiplap (either timber or UPVC - tbc)
- will either use ply or plasterboard on the wall/ceiling - tbc


Is there anything here that is fundamentally wrong, or anything I should watch out for? It will only be used as my home office, for the washer/drier and some storage for tools (i'll build an internal partition later). The doors and windows will all be vented, and i'll add some leccy panel heaters.

Couple of notes:

- I know this often comes up but I can't tear it down as there's a LOT of land up against it and I dont want to risk any wider damage to the garden / can't afford the cost of a substantial retaining wall right now. I'll do most of the work myself to keep costs down (just need my mates help with laying the EPDM roof)
- the insulation thicknesses came from looking at these fancy wooden office-sheds that i'm looking to copy on the cheap and they are often insulated at 25mm between the internal and external coverings
- I wont be drilling the concrete if I can help it
- the gate will be moving round the corner

I have attached a picture of her in all her dated glory.

I'd advise anyone attempting to improve a concrete sectional garage to approach it with trepidation. You have what is already a low end structure. Couple that with the fact that it is acting as a retaining wall (= damp - condensation - mould - rot), is not a very good start point.
In order to make it work, you would basically end up building a very expensive 'cell', concealed within a crappy outer skin.

 

[cdbe]

As above. But there seems to be some sort of retaining structure in the foreground(a prefab garage retaining that much land could be dangerous)? Looking at the height of the back corner you could probably build a separate lightweight building on top! The suggested insulation is inadequate.

 

[Ivor Windybottom]

If you are ever thinking of selling (possibly if you've outgrown it), then converting that into a dodgy office may devalue it.

Building a proper new office from scratch would cost more but add value.