crazySteve
Member
Hi Chaps,
Just stumbled across this forum while desperately searching for answers, I really need some good sensible help and advise on my shed muck-up.
So during the summer 2019 I decided to build a 30m2 shed at the bottom of the garden as a games room/ snooker room/ workshop. The construction goes as follows:
Reinforced concrete slab with a visqueen DCP layer sat on a MOT compacted stone base. The walls framework is build from 4x2" C24 (none treated) CLS timber, the walls are 400mm centres with loft insulation stuffed in between. On the outside I have a breather membrane stapled to the 4x2" and I have fixed 12mm shuttering PLY over the membrane directly to the 4x2" frame (first mistake no air gap). The back and two side are clad with the PLY to save cost but the front is clad with 20mm treated timber gravel boards. Also to note the walls do overhang the slab by 10mm or so and the extra visqueen from the slab is stapled to the base plate of the timber wall before the membrane was added, all to prevent water from reaching the dry slab.
The roof is constructed with DIY 'A-Frame' designed trusses which are basically C24 4x2" CLS joined with an A-shaped piece shuttering PLY to give strength and to set the pitch, the design worked well and allowed for a shallow pitched roof that was strong. As with the wall the trusses are at 400mm centres and stapled to this again is the breather membrane and the 12mm shuttering PLY boards (no air gap), I then covered the shed with good quality roofing felt.
The roof is insulated with 100mm loft insulation, there is a slight gap in the A of the frame where to 100mm insulation didn't fill the void, but I left this clear. Internally I boarded both the walls and ceiling with with 9mm shuttering PLY.
There are two windows (none opening), double glazed units on the front and a door to the side.
As I say I started the project in the summer but progress has been slow and I only finished boarding the inside probably around Oct/Nov. Since then I've been only able to work on completing the shed in the evenings and weekends.
Because I still don't have any permanent heating in the shed yet anytime I go down there I usually just have my small 1KW electric heater which does a OK job of heating the room, after an hour or so the temperature will go from 6/7c to 14/15c, so I assume the insulation is doing some good!
The problem I've now noticed gradually over the past 6/7 weeks is green/blue fluffy mould appearing on the PLY boards around the bottom 100mm of the shed perimeter (internally), I have also noticed the odd small area on the ceiling and higher up the walls and corners, and overall it seems to be getting worse! Yesterday I unscrewed a couple of the internal PLY boards to investigate what is actually going on, I did notice the backs of the boards are no worse than the front, fortunately! But still the mould is there at the bottom. I also removed some of the insulation and the back of the breather membrane does feel 'sweaty' the 4x2" CLS frame also felt a bit damp to the touch. I then took a small section of the ceiling PLY down, the board had no signs of mould, but when I felt past the insulation to the membrane on the underside of the roof, it feels Very Sweaty!
So thats where I'm at with my problems.... I've pretty much spent all the funds I can afford on the shed and it's upsetting to see mould issues already. I realise now I've made errors with not introducing air gaps but the reality is it's a bit late in the day and too much money has been spent to start again so I need to somehow work with what I've got.
Can anyone please give me some advice on how best to tackle the problem, I realise there have been a few mistakes so please no 'if you'd have done it like this' scenarios...
I've read adding a VCL vapour barrier to the warm side of the insulation (between the insulation and internal PLY) will stop warm moist air getting through to the insulation and reduce condensation on the membrane? That would hopefully stop the 4x2" timber from getting moist also? Externally I could take the boards off in the summer and batten them off the frame to create an air gap, but the problem is what do I do with the roof? stripping the roof isn't an option.
Sorry for babbling on.. hopefully there's enough info there, but happy to answer any questions if it help to get this fixed.
Cheers
Steve
Just stumbled across this forum while desperately searching for answers, I really need some good sensible help and advise on my shed muck-up.
So during the summer 2019 I decided to build a 30m2 shed at the bottom of the garden as a games room/ snooker room/ workshop. The construction goes as follows:
Reinforced concrete slab with a visqueen DCP layer sat on a MOT compacted stone base. The walls framework is build from 4x2" C24 (none treated) CLS timber, the walls are 400mm centres with loft insulation stuffed in between. On the outside I have a breather membrane stapled to the 4x2" and I have fixed 12mm shuttering PLY over the membrane directly to the 4x2" frame (first mistake no air gap). The back and two side are clad with the PLY to save cost but the front is clad with 20mm treated timber gravel boards. Also to note the walls do overhang the slab by 10mm or so and the extra visqueen from the slab is stapled to the base plate of the timber wall before the membrane was added, all to prevent water from reaching the dry slab.
The roof is constructed with DIY 'A-Frame' designed trusses which are basically C24 4x2" CLS joined with an A-shaped piece shuttering PLY to give strength and to set the pitch, the design worked well and allowed for a shallow pitched roof that was strong. As with the wall the trusses are at 400mm centres and stapled to this again is the breather membrane and the 12mm shuttering PLY boards (no air gap), I then covered the shed with good quality roofing felt.
The roof is insulated with 100mm loft insulation, there is a slight gap in the A of the frame where to 100mm insulation didn't fill the void, but I left this clear. Internally I boarded both the walls and ceiling with with 9mm shuttering PLY.
There are two windows (none opening), double glazed units on the front and a door to the side.
As I say I started the project in the summer but progress has been slow and I only finished boarding the inside probably around Oct/Nov. Since then I've been only able to work on completing the shed in the evenings and weekends.
Because I still don't have any permanent heating in the shed yet anytime I go down there I usually just have my small 1KW electric heater which does a OK job of heating the room, after an hour or so the temperature will go from 6/7c to 14/15c, so I assume the insulation is doing some good!
The problem I've now noticed gradually over the past 6/7 weeks is green/blue fluffy mould appearing on the PLY boards around the bottom 100mm of the shed perimeter (internally), I have also noticed the odd small area on the ceiling and higher up the walls and corners, and overall it seems to be getting worse! Yesterday I unscrewed a couple of the internal PLY boards to investigate what is actually going on, I did notice the backs of the boards are no worse than the front, fortunately! But still the mould is there at the bottom. I also removed some of the insulation and the back of the breather membrane does feel 'sweaty' the 4x2" CLS frame also felt a bit damp to the touch. I then took a small section of the ceiling PLY down, the board had no signs of mould, but when I felt past the insulation to the membrane on the underside of the roof, it feels Very Sweaty!
So thats where I'm at with my problems.... I've pretty much spent all the funds I can afford on the shed and it's upsetting to see mould issues already. I realise now I've made errors with not introducing air gaps but the reality is it's a bit late in the day and too much money has been spent to start again so I need to somehow work with what I've got.
Can anyone please give me some advice on how best to tackle the problem, I realise there have been a few mistakes so please no 'if you'd have done it like this' scenarios...
I've read adding a VCL vapour barrier to the warm side of the insulation (between the insulation and internal PLY) will stop warm moist air getting through to the insulation and reduce condensation on the membrane? That would hopefully stop the 4x2" timber from getting moist also? Externally I could take the boards off in the summer and batten them off the frame to create an air gap, but the problem is what do I do with the roof? stripping the roof isn't an option.
Sorry for babbling on.. hopefully there's enough info there, but happy to answer any questions if it help to get this fixed.
Cheers
Steve