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How to continue my shed project with condensation forming

Postby Delta_Tango93 » Fri Sep 04, 2020 8:53 am

Hi, I've read countless forums, watched days worth of YouTube videos and spoken to multiple manufacturers (most pretty unhelpful to be honest) and have come to an ultimatum, but want an opinion on if I'm actually on the right track or not, and if anyone knows of a better solution...

I have a small tool shed W181cm x L294cm x H194cm, that I'm converting into a workspace.

It originally had water ingress in one bottom corner, not from the ceiling. One wall of the corner being an internal shared wall with the neighbour's shed, and the 294cm long side wall being covered in neighbour's external vegetation that I cannot access. It also had a damp ceiling due to no protection and vegetation on the flat roof.

It's a single layer red brick building (no inner wall or wall cavity) with DPC, a flat concrete roof (ceiling actually had old newspaper Papier machéd in some places!) and a solid bare concrete floor.

None of the walls have an air vent, air brick, weep, etc. There is one wooden framed single glazed window on the wall opposite the mentioned corner, but it does not open and I will be replacing this with a upvc double glazed window with a trickle vent. The door is rotting away with holes in the wood and I'll also be replacing this.

So far, I have
- Cleared the roof of vegetation and applied Bostik Flexacryl.

- To the floor, I applied 2 coats of Permaguard epoxy resin DPM, with the second containing aggregate to stick a wood floor down.

- Repointed where needed and to all 4 walls internally, covering every inch, 2 layers of grey KA tanking slurry with a 3rd layer in the specified corner.

- To the wall/floor and wall/ceiling joints, fillet sealant and keeping the door (which has rotted away and has a few holes in) open as much as possible.

The condition has vastly improved, but clear water droplets were visible every morning if I kept the door closed, in the affected corner only.

KA tanking have told me that because the water is crystal clear, it is condensation and not water ingress which would contain sediment. They also said to wait 14 days after the last coat before looking at boarding or insulating over it, to allow the tanking to fully cure, dry and to keep ventilated as much as possible. It has been 3 full days so far, and appreciate the problem may just resolve itself, but want to be a step ahead of the game if possible. If it's just a case of waiting, that's fine with me.

I am wanting to line the entire inside with plywood by screwing battens into the brick walls and ceiling (with silicone sealant and wall plugs of course) so I'm reluctant to use air bricks or vents as I believe they need to stay exposed, but it looks like I may need to use a different method if the condensation still occurs after changing the window, door and waiting 14 days.

I'm looking into the following options...
- Gyproc Thermaline Plus or Super, dot and dabbed using instastik polyurethane foam adhesive and dryzone dry grip adhesive.

- Or using the same adhesive, to apply just the plywood,

- Or to continue with my original batten and plywood plan.

- Or batten, fit with foil backed insulation board and ply over the top.

Which do you think is best, or can you recommend a better way? Having a permanent dry space is my main priority, followed by preservation of space and of course, budget and time.

Thank you for your time, and my apologies for the lengthiness of this post. Please go easy on me, I'm a first time diy forum poster and not a professional.
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Simply Build It

Postby stoneyboy » Sun Sep 06, 2020 11:01 am

Hi delta_tango93
Reading between the lines I assume you are hoping to end up with a dry shed that you can use and occupy. The fact that you have a single skin structure means that condensation is a possibility especially in colder weather. This is most likely to run down the walls and end up on the floor especially now you have sealed the two together. Hope you do not find this too problematical.
Regards S
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