Flat roof to existing pebbledash wall - leaking

[Jonhhy27]

Hi All

We a single story flat roof extension built around 3 years ago but has been leaking in the same area during long periods of wind driven heavy rain.

New lead flashing has been chased 20-25mm into the pebbledash wall around all elevations. At the corner, our builder has patched up the possible leak source with flashband and lots of sealants (see photos) during the build. A mess I know. This worked for a few months but started to leak again. My builder keeps making excuses now and refusing to come back out.

I think wind driven rain is hitting the pebbledash wall, running down and along the bottom pitched bell cast / drip tray. Eventually somehow getting inside the corner patch repairs and into the house internally. The builder has tried applying lots of sealants to stop this happening.

I think the only solution would be to get a roofer to rip out the corner and fix it properly. Before I engage with roofers, just wondering if anyone can offer any guidance?

the photos show the corner detail in question as well as location of leak internally. I’ve also taken a photo looking up inside the pebbledash wall.

 

[tell80]

The lead flashing should be chased 25mm into the wall itself, that means 25mm beyond the render and dash.
The lead flashing covering the profile tiles looks wrong unless there is a continuous secret gutter tight to the wall, maybe thats what you a. profile tiles usualy take one-piece step and cover flashings in 1.5m lengths.
The flat roof at the outside corner has been repairpatched a number of times. Different materials used.
The whole mess from the corner to the piched roofneeds removing to trace any leak patterns and
re-do properly. maybe round the corner as well? why the plinths, who put them in?
How does the pitched roof met the flat roof?

looking upinto the cavity am i seeing cav insulation in the ccavity but no cavity trays.? cavity trays areusualy used where the lower pitched roof meets the wall. does it matter now i dont know? Is there a breakthrough lintel below or any damp?

 

[Jonhhy27]

Thanks. The flat roofing rubber extends under and past the pitched tiles. I’ve lifted the bottom row of tiles to have a look before but seems dry and hence why I’ve suspected the dodgy corner detail. The plinth against the pebbledash wall is rigid insulation as per architect’s detail.

The cavity photo shows mortar. No cavity trays. I thought pebbledash/render walls are generally impervious?

 

[tell80]

The plinth or upstand insulation isnt needed, its trapping water but if its specified then aangle filet should lead the EPDm up the plinth. or better no upstand just a angle filet to take the rubber roofing up to the chase. The render and dash should end with a Bellcast fixed above the chase.

Whats the mortar doing in thecavity besides bridging it? is it supposed to act as a cav tray and prevent water dropping down? pics of surfacesdirectly below would help.Does the gable bedroom show water damage?

and pics of the outside lead
secret gutter, what you call a drip tray. show it with a few tiles lifted?
render an dash are not imprevious to penetrating waterr.

 

[Jonhhy27]

Thanks for the suggestions. I’ve got a roofer coming over this weekend and will mention these to him.

Not sure why there’s mortar in the cavity to be honest. Its always been there I believe. No water ingress to the gable room.

See photos:

1) photo looking upstream on the secret gutter

2) 1st tile removed. I believe my extension builder put mortar there to try to divert water away.

3) 2nd tile removed. I also removed the mortar as it doesnt look right and could potentially trap rainwater

4,5,6) various photos of batten which was previously covered in the mortar. You can rusted nail head on the secret gutter flashing and dampness in the batten downstream which indicates a source of water ingress.

 

[tell80]

The new pics are great.
As you go up a roof each newlayer of flashing orfelt goes over the layerbelow.The lead strip at the bottom of your pitched roof is on top ofthe felt not below it so any
water coming down thefelt could go under the EPDM?

The secret gutter is a mess. youwill need to remove all adjoining tiles and the soakers at the bottom. And lift lft the wholesecret gutter out aand flip up the cover flashing flaps for a pic or two. the proper way to do it over profiled tiles is to fit whats called one piece stepped cover flashing - google some pics. secret gutters should be avoided.

Problem for roofer quoting they cant see the full extent of the damage. eg the roof boards or joists could be water rotted. Is the flat roof sqishy anywhere?