Leaking Roof

[Leakyroof]

For more than a year now, my partner and I have been trying to pinpoint the root cause of a leak on our roof and have roof works done, but in vain. The roof is still leaking.

 

Our roofers have confirmed and done the following:

- Coping stones are less than 10 year old (unlikely to be porous)

- Coping stones have dpc underneath them (protection from water ingress if coping stones were failing)

- Replaced the lead flashing (to correct position if lead flashing had moved/slid and caused the leak) 

- Re-rendered the parapet wall (to avoid having any cracks in the render that might have caused the leak)

- Repointed the joint between the coping stones (to avoid water seeping through between the coping stones)

 

Need confirmation:

- dpc under the coping stones has been applied, but probably not unders the last coping stone (old sandstone keystone at the front)

- water test (buckets / watering cans) splashing onto the coping stones - no results

- water test (buckets / watering cans) splashing onto the tiles / flashing - water ingress wall, but slightly further up the party wall, NOT where the usual leak is occuring

 

Potential root cause > proposed solutions by our roofer:

- last coping stone failing (block keystone, sandstone) > cap the coping stones with torch / felt system

- head lap coverage of each tile / lead soaker issue > front elevation needs to be redone at the correct batten spacing to increase tile head lap

 

Other potential root cause:

- cracks / missing render on parapet wall (neighbours' side) allowing water to penetrate / run through the coping stones and appear on our side? > (roofer's answer: highly unlikely to cause an issue to your property unless they have the same issue in the same place)

 

How would you resolve this issue?

[jack]

Welcome.

 

I'm certainly no specialist, but I'd start with the fact that the coping stones don't appear to have any sort of drip edge on them. If so, water will track underneath them to where they join the render. Any cracks/gaps at that joint will let in water.

 

Re "Coping stones have dpc underneath them (protection from water ingress if coping stones were failing)", what does the DPC actually cover? If it's just the top of the wall under the coping stones, the water behind the render will find its way to the brick wall once it gets lower than the bottom of the DPC.  

 

Before rendering, the brickwork looked very "gappy". Any water getting though to the brickwork could take any number of paths downwards, including from one side of the wall to the other (e.g., it's possible water getting on on your neighbour's side could track to your side through a gap in the mortar).

 

I'm sure someone more knowledgeable will be along shortly, but having dealt with a serious roof leak in the past, you have my sympathy!