Hi would really appreciate advice on finding the source of and repairing a roof leak. Setting - Victorian terraced house. At some point kitchen had a single storey extension out at the back through removal of part of downstairs rear wall (above which the brickwork is supported by RSJ). The extension roof has a pitch of about 5 degrees. It is around 3m wide front to back but supported along its length by another RSJ which rests on the other one. The reason for having a beam to shorten the span to 1.5m is because the extension carries the extra weight of a "green roof" consisting felt and sedum plants.
A few years ago, just prior to laying the green roof we had the extension re-reroofed using roofing felt. Thick plastic liner is laid free floating on top of that and weighed down by the green roof (felt substrate and plants). Along one side and top of the extension is brickwork - on one side the upper floor of the house, and down the kitchen is our neighbour's kitchen extension - the top of their roof is a couple of feet higher than ours.
The felt on our roof is made to come up the wall by a couple of inches or so. Then there is lead flashing all the way around that is cemented into the wall and comes down past where the felt goes up to and then is squashed down onto the felt for a few inches.
Despite checking meticulously for gaps, and despite having put sealant in any visible cracks and crevices, whenever it rains heavily we get a little shower coming down in the kitchen, always at the same point which is halfway down the roof where the lengthways RSJ rests perpendicular on the earlier RSJ. There are no damp patches on the ceiling that would indicate water coming in at any point higher than the halfway point where the beam is. I have already squirted sealant all along the top of the lead flashing and along all joints in flashing. I have spent a couple of hours on a dry day pointing a hose at every point around where the edge of the roof meets either of the walls. I have saturated the green roof plants with the hose. Yet none of that resulted in any water coming into the kitchen.
Photo of where the new beam meets the original beam (you can't see the steel as it's covered in fireproof cladding and an oak covering). On the right hand side below the wooden covering you can see a dark dribble of water where it meets the wall.
Photo of outside of roof looking towards back of house (I have sealed extensively using a grey sealant over every joint and crevice):
Plan of back of house showing where water is coming in inside the kitchen:
I've had the original roofer back numerous times and he can't find any cause for the leak. He suggested applying roofing tape (and painting some sort of primer so it would stick) on the brickwork and the lead to cover the gap between brickwork and lead flashing, and then again on the lead and the felt to cover that gap. Does that sound reasonable, and has he missed anything? If two hours of hosing it down isn't able to find the leak what chance do I have of finding it any other way?
One other comment - the previous occupants of the house told us they also had a leak in the same place for some years until a roofer fixed it somehow. So whilst I suppose it's possible the leak could be anywhere on the roof and is tracking along the oak cladding of the RSJ until it reaches the wall, that does seem unlikely given previous problems coming through at the same point and brand new felt applied recently.
A few years ago, just prior to laying the green roof we had the extension re-reroofed using roofing felt. Thick plastic liner is laid free floating on top of that and weighed down by the green roof (felt substrate and plants). Along one side and top of the extension is brickwork - on one side the upper floor of the house, and down the kitchen is our neighbour's kitchen extension - the top of their roof is a couple of feet higher than ours.
The felt on our roof is made to come up the wall by a couple of inches or so. Then there is lead flashing all the way around that is cemented into the wall and comes down past where the felt goes up to and then is squashed down onto the felt for a few inches.
Despite checking meticulously for gaps, and despite having put sealant in any visible cracks and crevices, whenever it rains heavily we get a little shower coming down in the kitchen, always at the same point which is halfway down the roof where the lengthways RSJ rests perpendicular on the earlier RSJ. There are no damp patches on the ceiling that would indicate water coming in at any point higher than the halfway point where the beam is. I have already squirted sealant all along the top of the lead flashing and along all joints in flashing. I have spent a couple of hours on a dry day pointing a hose at every point around where the edge of the roof meets either of the walls. I have saturated the green roof plants with the hose. Yet none of that resulted in any water coming into the kitchen.
Photo of where the new beam meets the original beam (you can't see the steel as it's covered in fireproof cladding and an oak covering). On the right hand side below the wooden covering you can see a dark dribble of water where it meets the wall.
Photo of outside of roof looking towards back of house (I have sealed extensively using a grey sealant over every joint and crevice):
Plan of back of house showing where water is coming in inside the kitchen:
I've had the original roofer back numerous times and he can't find any cause for the leak. He suggested applying roofing tape (and painting some sort of primer so it would stick) on the brickwork and the lead to cover the gap between brickwork and lead flashing, and then again on the lead and the felt to cover that gap. Does that sound reasonable, and has he missed anything? If two hours of hosing it down isn't able to find the leak what chance do I have of finding it any other way?
One other comment - the previous occupants of the house told us they also had a leak in the same place for some years until a roofer fixed it somehow. So whilst I suppose it's possible the leak could be anywhere on the roof and is tracking along the oak cladding of the RSJ until it reaches the wall, that does seem unlikely given previous problems coming through at the same point and brand new felt applied recently.
