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

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, 20233 yr by Kelvin

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 !

I see. It could cause all sorts of structural problems. Wouldn’t you be better biting the bullet now and redoing? 

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?

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 

 

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?

 

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 ?!

Or could use this for our ceiling, below the joists ?

 

(Taking special care to seal any penetrations)

Edited July 3, 20233 yr by bmj1

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.

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.

7 hours ago, goodbyegti said:

 

And all the wiring and downlights is below the VCL?

Correct, all wiring below VCL. Not much room. You can see the void in the diagram.

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.

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'. 

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.