Flat roof leak or condensation ?

[andrewlato81]

Hi all,
I am having issue with water coming into extension where it joins conservatory. Problem only occurs in wet weather. Flat roof constructed 2 y ago , pvc covered sheet with anti-drip. rafters 225, 120 insulation between rafters and 20 foil back kingspan under rafters(been told this is to act as a VCL). now I have had this issue discussed here and managed (with help from ppl on here) to improve ventilation at the bottom of roof.the problem has gone away except to the corner pictured it seems to be getting worse. My Q's is how else can I improve ventilation thru that corner? I am about to lift the sheets coz I just dont know what else to do. I am sure there is no holes in sheets and the only thing that may be causing it is either condensation or water being pushed back under it with wind- however the corner is well covered on the outside so maybe wind just cant get there to dry it out???
Many thanks for all help
Andre

 

[KenGMac]

andrewlato81, Hi

Is there any possibility that the under slating felt is in effect dumping some rain water into that position?

If the original main roof felt which at one time was ending up in the gutter, where is it going now?

Ken.

 

[catlad]

Unorthodox

 

[^woody^]

Unorthodox

Understatement

 

[^woody^]

If it happens when it rains, then it's not condensation. The type of staining points to a leak too.

You'll just have to do the usual investigation based on common sense.

The only obvious things I can see are no filler pieces are the eaves, and screws in the sheet troughs which should not be there.

 

[catlad]

Woody you are supposed to screw them in that position they are self tapping and sealing fixings.

 

[andrewlato81]

andrewlato81, Hi

Is there any possibility that the under slating felt is in effect dumping some rain water into that position?

If the original main roof felt which at one time was ending up in the gutter, where is it going now?

Ken.

Hi Ken
The underlay on main roof now sits on the top of sheets so I dont think water is running from the top of flat roof to it's bottom.

 

[andrewlato81]

Had a busy day today.Lifted all sheets on small section of flat roof and above the corner where it leaked. I discovered that whoever built the roof has not placed any insulation above that corner-see pics-. There is an empty void above corner - could it be that warm air from house meets cold air and causes so much condensation that it leaks?What makes me wonder is that in and around that void the timbers are rather dry.
Also as you will see from pics the timber battens at the bottom of roof are wet especially second row( barge board covers first row only) - is there not enough ventilation? Would cutting holes to the front of barge board and fitting 65mm round vents help?
My other theory is- water getting under sheets by capilary action or wind, goes back a bit and if the roof 'sinked' a bit in that corner, that would create slight slope on barge board ( section under sheets) allowing water to travel off barge board and drip right in that corner??? I need long level to check this out and should get one Monday.
Roof is only ventilated at the top and bottom- should I do the sides too ? Roof has a slope of 6% or around 3.5deg if this helps.
Any other thoughts please?

 

[andrewlato81]

If it happens when it rains, then it's not condensation. The type of staining points to a leak too.

You'll just have to do the usual investigation based on common sense.

The only obvious things I can see are no filler pieces are the eaves, and screws in the sheet troughs which should not be there.

Hi Woody,
I took the fillers out and replaced them with brushes similar to gutter protectors to improve ventilation. Now having second thoughts of putting them back to somehow limit water traveling back on antidrip.Screws are self sealing.