Making a "Garden store" more like a room

10 Aug 2021
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United Kingdom

First time posting on here as I'm not sure what to do next with a garden store that we have at the back of the house.

When we bought the house back at the start of 2019, we were told this room was a "garden store". The bloke that we bought the house from, used it to fix up his motorbikes. My aim was to use it as an office and a sort of (for lack of a better word) "man cave".

Here is what it looked like when we moved in:

Its a nice space (about 12m squared), but the roof is corrugated plastic, the wall to the right of the picture is plastic slats and there was loose bits of wood around the window.
So I attempted to brick up around the window. It ended up ok, albeit a bit messy. Not too bad at a first attempt of brick work. I made sure that I placed metals brackets in the cement and screwed into the wall and window frame. Everything is now very solid and has been sitting there nicely for a couple of years.

Heres what it looked like after fitting a blind and chucking in an Ikea desk:

I've also insulated the roof with Kingspan. I was worried that I might get condensation problems, but fingers crossed, I haven't had any condensation issues since I installed the insulation last summer:

I got a little water ingress from the block wall below the window, but that turned out to be a issue with the pointing in the wall on the outside. Fixed that and also applied some Storm Dry cream to the outside brickwork and its fine with no water or damp at all.

I have two issues that I want to tackle at the moment and I'm hoping someone here can advise on what I should do.

Firstly, the block/brick wall under the window is a really good conductor of cold and heat. My feet are by this wall and they get cold in the winter. The heat isn't so bad in the summer, its the cold that's the problem. Should I just insulate/plaster board this small wall? Do I need to render outside (its bare block/brickwork outside, but has the storm dry applied to it), or can I just get away with plasterboard?

Secondly, I have to move out of this room for a month or two over the winter as frost gets in under the plastic roof and then melts in the morning. Its not the insulation that causes this as the roof and floor tiles runs the whole length of the back of the house (as well as above this room) and has the same problem and drips the melted frost on to the tiles. Its not a lot of water, but I get some coming through the insulation and I move my computer etc out of there just in case some drips of water get into the computer.

Too be honest, the insulation was a temporary solution until I came up with a more permanent solution for the roof above the room. I was thinking of maybe a super lite roof or something like that. Or is there a way to stop the frost getting under the plastic roof so I can have a bit more time before I find a permanent solution.
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Do you know when it was built? You might want to apply for a certificate of lawful development before you start.

I’d tank it in 100mm celotex plaster board it and install reversible aircon to heat and cool it. For the roof, maybe tripe coat shed roll or rubber.
I did ask our neighbours when the roof/room/tiling was added to the back of the house. They advised that it had always been there ever since they moved in more than 20-25 years ago! I don't think we have any certificates for it. I think we have looked through the docs when we bought it, but I don't think there is anything in there. I think the bloke we bought it from re-did the block brickwork under the window as that looks newish. I'll look into into that lawful certificate, however at the moment, I'm not making major changes/investment into this until I've decided what I'm doing with the roof. I've only spent approx £150 on insulation and whatever the bricks and cement cost to brick around the window.

If I can insulate that wall without rendering on the outside, that would be great. If I add 100mm insulation/plasterboard, the window will then be "recessed" away from the new wall of insulation. Do I then make an internal "window sill" with plasterboard or something similar? Currently the Window is flush with the brickwork at the bottom and the sides.

I'm already saving up for a mini split heat pump to heat and cool it. Its definitely the most efficient way of heating a single room. I'll wait to do that, again once I know what I am doing with the roof.

I'm not sure what the triple coat shed roll stuff is. I've done a quick google, but I'm not sure what I'm looking for.
The only thing that I worry with this roof is that it might leak. Touch wood, its fine at the moment, but as its been here for some time, I think at some point in the next few years, it's going to have to be replaced with something more permanent. We did have a super lite roof installed on our leaky conservatory in our old house. It was nice, but expensive. I'm wondering if there are any other options roof wise. I don't know what sort of foundations are underneath this tiled floor, so a "proper" roof might be out of the question. I've got £7-£8K set aside potentially for a new roof if I need one, but would prefer not to spend all of it on the roof, as the plastic slatted "wall" will need to be sorted at some point (maybe sealed and insulated).
Sorry I was typing on the mobile..

Shed roof felt, over lapping 30-50% one layer of underlay (fine) and one layer of standard felt. Start at the bottom and work up. With the overlap, you will get to 3-4 layers total. Mastic it at the edges. Think 1960s garage.

before that you need to board it with OSB and joists if the current aren't good enough. 8" at 400-600mm spacing depending on the span.

the 100mm celotex can be stuck directly to the inside of the wall, with plasterboard foam and then you stick the plasterboard to that in the same way. You could go 70mm or even 50mm to save cost. On the roof you need between and overlapping (cold roof)


100mm +50mm (roof) will make it compliant with current standards. It will only ever be a "store room" unless you get building control and certificate of lawful development. The floor also needs to be done assuming its an uninsulated slab.

cheap aircon under 400 quid:
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Thanks for the info. Much appreciated. If I stick 100mm of Celotex/insulation on the wall and around the window, I'm going to be "pulling" the wall out by 100mm and therefore 100mm away from the window which is currently flush with the brickwork. I've done some googling but I'm not sure what to do "square off" around the window. Just adding the insulation/plasterboard is going to leave exposed insulation around the window. Whats best to cover this? Just some additional plaster board?
44C5B1EA-0AAB-4F0B-9A54-369D1636463E.jpeg The window board may need to be either expanded or replaced. The edges of the wall are just sealed with plasterboard and filled with expanding foam if needed.


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Ok, so its been a while since I've updated this thread. After several quotes, we got a reputable roofer in and he removed the plastic roof above the room and replaced with a cold roof, similar to the one described above. Cost just over £1000. So that's now done and hopefully that's now sorted. I've bought a roll of this vapour barrier:

About 10m of it should cover the insulated ceiling (then 15m remaining). That will be attached on to the insulation (again as suggested above) as even though I have taped the gaps in between the insulation boards, I want to make sure that a minimal amount of warm air goes into the cold roof.

The next thing on the agenda after that has been done is to insulate the windowed wall pictured above with 100mm insulated plasterboard.

What would be the best way to attach the insulation boards to the block work below and around the window?
Also, I'll have loads of this vapour barrier left over after using it on the ceiling that I could use for the wall. What would be the best way to install insulated plaster board along with a vapour barrier?
Ok, long time without updating again. I’ve finally got around to battening the external walls. 50mm of insulation between the battens and eventually insulated plasterboard on top of the vapour barrier that I’ve done some of already:


Before I can install the insulated plasterboard I’ve got to get some electrical sockets installed as I’ve only got one double socket in this room at the moment. I’ve got an electrician that is going to come out and terminate the twin and earth to the sockets, but I’m going to run the cables before hand. I’ve decided to put in a false ceiling which will help with many things but the main thing being that I can hide the cables above it. I’ve added a frame around the room (see the 2x4 attached to the stud wall in the first picture) for the joists to sit on top of and my cables will be above this and come down through the frame and clipped to the brick walls and down to the new sockets.

My question is, what is the best practice for routing the cables from the ceiling and down to the sockets? This is a radial circuit BTW. Should I route the cable down to each socket from above where the ceiling will be, into the socket and then back up into the ceiling so that each socket is daisy chained, or have some kind of junction box in the ceiling above each socket and run the one cable down to each socket rather than looping back up again?

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