Hi all,
I posted a thread about my garden room in the 'Building' section of the forum, but many of my questions relate to my roof problems, so I thought I'm better off posting those here.
I've had a garden room half built and have had to send the builders packing after a poor job. Now I'm trying to see what can be done about it to make it useable. The roof is a flat roof which was supposed to be done in EPDM, but they arrived with narrow rolls of Cortex EPDM membrane which they stuck down but have left lots of loose seams and leaks around the flashing where it's not even bonded down. The roof is about 6m wide and 3m deep.
I think the pitch is something like a 3cm fall to the front along most of its width, but at the left corner is actually pitches to the back and side a little bit. The red arrows indicate what I think it’s doing, but mostly it’s more or less flat.
I’ve been considering various options for improving things, which will mainly mean re-doing the flashing (with something like this) and sealing the whole surface, but might include increasing the pitch.
- To entirely redo the surface in EPDM I would need to remove the existing EPDM membrane back to the OSB/3, or overboard the EPDM without removing it. Overboarding with OSB would be difficult for me, but also add far more weight to the structure than I want. In order to install wedges and raise the pitch though I would need good strong boards, like 18mm. If I don’t change the pitch though perhaps an alternative is just overboarding with lightweight 4mm WBP Ply External Plywood. 6 boards would only weight about 42kg as opposed to almost 200kg of 18mm. Not to mention the new EPDM which may be another 50kg. 4mm might warp and lift too easily though. Should I be concerned about this, or just go for it? Alternatively is 12mm likely to be adequate, or maybe 8 or 10mm, given that these are just going to be sitting on existing 18mm boards? Strength isn’t an issue because it would just be screwed right on top of the existing surface, and then another EPDM sheet stuck on this.
- I could also try ripping up the EPDM and replacing it with a proper one without overboarding, but that could be long and messy. It would also no doubt leave a lot of thick mastic behind and I'm told a roofer would not want work with the surface like that. It would still need to be overboarded. Is that correct?
- Another alternative a colleague suggested was just sealing the existing EPDM properly and then overlaying it with lightweight Polycarbonate boards to create an additional layer. I might even be able to investigate lifting it higher at the back using spacers or batons to improve the pitch, but obviously the structure won’t be strong enough to stand on, (not that this will matter)
- I guess corrugated PVC board could be used as well as it’s cheap. None of this will be seen from the ground as it’ll hidden behind the fascia and guttering that it’ll overhang into I guess.
Any advice or suggestions?
Thanks!
I posted a thread about my garden room in the 'Building' section of the forum, but many of my questions relate to my roof problems, so I thought I'm better off posting those here.
I've had a garden room half built and have had to send the builders packing after a poor job. Now I'm trying to see what can be done about it to make it useable. The roof is a flat roof which was supposed to be done in EPDM, but they arrived with narrow rolls of Cortex EPDM membrane which they stuck down but have left lots of loose seams and leaks around the flashing where it's not even bonded down. The roof is about 6m wide and 3m deep.
I think the pitch is something like a 3cm fall to the front along most of its width, but at the left corner is actually pitches to the back and side a little bit. The red arrows indicate what I think it’s doing, but mostly it’s more or less flat.
I’ve been considering various options for improving things, which will mainly mean re-doing the flashing (with something like this) and sealing the whole surface, but might include increasing the pitch.
- To entirely redo the surface in EPDM I would need to remove the existing EPDM membrane back to the OSB/3, or overboard the EPDM without removing it. Overboarding with OSB would be difficult for me, but also add far more weight to the structure than I want. In order to install wedges and raise the pitch though I would need good strong boards, like 18mm. If I don’t change the pitch though perhaps an alternative is just overboarding with lightweight 4mm WBP Ply External Plywood. 6 boards would only weight about 42kg as opposed to almost 200kg of 18mm. Not to mention the new EPDM which may be another 50kg. 4mm might warp and lift too easily though. Should I be concerned about this, or just go for it? Alternatively is 12mm likely to be adequate, or maybe 8 or 10mm, given that these are just going to be sitting on existing 18mm boards? Strength isn’t an issue because it would just be screwed right on top of the existing surface, and then another EPDM sheet stuck on this.
- I could also try ripping up the EPDM and replacing it with a proper one without overboarding, but that could be long and messy. It would also no doubt leave a lot of thick mastic behind and I'm told a roofer would not want work with the surface like that. It would still need to be overboarded. Is that correct?
- Another alternative a colleague suggested was just sealing the existing EPDM properly and then overlaying it with lightweight Polycarbonate boards to create an additional layer. I might even be able to investigate lifting it higher at the back using spacers or batons to improve the pitch, but obviously the structure won’t be strong enough to stand on, (not that this will matter)
- I guess corrugated PVC board could be used as well as it’s cheap. None of this will be seen from the ground as it’ll hidden behind the fascia and guttering that it’ll overhang into I guess.
Any advice or suggestions?
Thanks!
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