bmj1 Posted July 3, 2023 Share Posted July 3, 2023 Hi all, I've got a newly built warm flat roof that I've been advised is likely to fail at some point over the next few years due to an error in the build-up / interstitial condensation. Instead of replacing it today, I'd prefer to try and get a few years of use out of it, and rebuild it down the road when finances are hopefully a bit looser.. Any thoughts on some kind of moisture meter I could install, and where I should locate it ? I.e. would between the joists be sufficient ? We'll be running services between the joists and then plaster-boarding below Link to comment Share on other sites More sharing options...
Kelvin Posted July 3, 2023 Share Posted July 3, 2023 (edited) What’s the error? You can buy Wi-Fi hygrometers for wine cellars etc That might work. https://uk.govee.com/products/wi-fi-temperature-humidity-sensor?currency=GBP&variant=41546205069485&utm_medium=cpc&utm_source=google&utm_campaign=Google Shopping&utm_campaign=pla-lp&utm_source=google&utm_medium=cpc&gclid=EAIaIQobChMIzcvOxI_z_wIVBIVoCR3oRAP3EAQYAyABEgKIvvD_BwE https://www.energycontrol.com/Shop-Categories/Humidity/Remote-Mount-Humidity-Sensors Edited July 3, 2023 by Kelvin Link to comment Share on other sites More sharing options...
bmj1 Posted July 3, 2023 Author Share Posted July 3, 2023 14 minutes ago, Kelvin said: What’s the error? You can buy Wi-Fi hygrometers for wine cellars etc That might work. https://uk.govee.com/products/wi-fi-temperature-humidity-sensor?currency=GBP&variant=41546205069485&utm_medium=cpc&utm_source=google&utm_campaign=Google Shopping&utm_campaign=pla-lp&utm_source=google&utm_medium=cpc&gclid=EAIaIQobChMIzcvOxI_z_wIVBIVoCR3oRAP3EAQYAyABEgKIvvD_BwE https://www.energycontrol.com/Shop-Categories/Humidity/Remote-Mount-Humidity-Sensors Polythene plastic loose laid was used instead of specified VCL. Spoke to a specialist flat roofing company today who advised me it's just a matter of time until it fails... But welcome alternative thoughts ! Link to comment Share on other sites More sharing options...
Kelvin Posted July 3, 2023 Share Posted July 3, 2023 I see. It could cause all sorts of structural problems. Wouldn’t you be better biting the bullet now and redoing? Link to comment Share on other sites More sharing options...
bmj1 Posted July 3, 2023 Author Share Posted July 3, 2023 23 minutes ago, Kelvin said: I see. It could cause all sorts of structural problems. Wouldn’t you be better biting the bullet now and redoing? Maybe... What kind of structural problems are you concerned about ? If the whole condensation issue is localised and contained above the deck I'm not sure what issues you foresee? Link to comment Share on other sites More sharing options...
Kelvin Posted July 3, 2023 Share Posted July 3, 2023 Can you be sure it will be contained? My various membranes have taken a real battering in places that I wouldn’t want to be relying on them to keep water out of the building Link to comment Share on other sites More sharing options...
bmj1 Posted July 3, 2023 Author Share Posted July 3, 2023 7 minutes ago, Kelvin said: Can you be sure it will be contained? My various membranes have taken a real battering in places that I wouldn’t want to be relying on them to keep water out of the building Just came across this thread: VCL paint from below as another possibility? Link to comment Share on other sites More sharing options...
bmj1 Posted July 3, 2023 Author Share Posted July 3, 2023 23 minutes ago, bmj1 said: Just came across this thread: VCL paint from below as another possibility? Or could I apply the VCL from underneath the joists? A bit more work, but feasible ?! Link to comment Share on other sites More sharing options...
bmj1 Posted July 3, 2023 Author Share Posted July 3, 2023 (edited) Or could use this for our ceiling, below the joists ? (Taking special care to seal any penetrations) Edited July 3, 2023 by bmj1 Link to comment Share on other sites More sharing options...
goodbyegti Posted August 1, 2023 Share Posted August 1, 2023 On 03/07/2023 at 21:10, bmj1 said: Or could I apply the VCL from underneath the joists? A bit more work, but feasible ?! That's actually what our architect has specified for our warm roof. On top of the OSB deck we have 150mm PIR, then a loose fill between the joists underneath with mineral wool. The joists are boarded over on the underside with 18mm OSB, then a VCL, then battens to form a service void, then plasterboard. Link to comment Share on other sites More sharing options...
Dave Jones Posted August 1, 2023 Share Posted August 1, 2023 all depends on the VCL and how its fitted. As long as its brought down the internal walls to seal the roof up should be fine. Link to comment Share on other sites More sharing options...
goodbyegti Posted August 1, 2023 Share Posted August 1, 2023 Link to comment Share on other sites More sharing options...
bmj1 Posted August 1, 2023 Author Share Posted August 1, 2023 7 hours ago, goodbyegti said: And all the wiring and downlights is below the VCL? Link to comment Share on other sites More sharing options...
goodbyegti Posted August 10, 2023 Share Posted August 10, 2023 Correct, all wiring below VCL. Not much room. You can see the void in the diagram. Link to comment Share on other sites More sharing options...
saveasteading Posted August 10, 2023 Share Posted August 10, 2023 3 hours ago, goodbyegti said: You can see the void in the diagram. so if it gets damp there, it will show on the ceiling. the top surface of the roof is not labelled on your drawing. If that is an internal gutter I'd be more concerned about that. Link to comment Share on other sites More sharing options...
goodbyegti Posted September 25, 2023 Share Posted September 25, 2023 On 10/08/2023 at 23:13, saveasteading said: so if it gets damp there, it will show on the ceiling. Why would it get damp there? It's below the insulation and 'warm'. Link to comment Share on other sites More sharing options...
saveasteading Posted September 25, 2023 Share Posted September 25, 2023 On 10/08/2023 at 23:13, saveasteading said: If that is an internal gutter I'd be more concerned about that. On 03/07/2023 at 18:57, bmj1 said: Any thoughts on some kind of moisture meter I could install, These are my points. 1. Don't bother with a meter, a wet ceiling would show soon enough. 2. internal gutters and downpipes are high risk. Link to comment Share on other sites More sharing options...
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