Leak on abutment roof to pebbledash wall

I have had a major leak on my 6 month old roof today. working in the room below and started to hear dripping during a heavy rain shower. Water then started to leak in quite a bit and then eased off even though it was still raining.
View media item 18125Rung the builder who constructed the roof to let him know and he is basically denying any responsibility for the problem saying that water is leaking through the pebbledash wall above and running down inside that.

This is the second time that the roof has leaked in the same place, previously happened 2 weeks after it was constructed and the problem was a gap in the mortar joint between the ridge tile and the wall. Have not had any leaks since until today.

I have been looking at the pebbledash wall and flashing tonight. The flashing has a 180mm coverage over the tiles with a 40mm upstand with probably 20mm going into the pebbledash wall taking into account the bend radius and probably 250mm width of flashing. I know that the slot for this had been cut with a grinder and pushed in and sealed with lead mastic.
There was previously a plastic roof with flashing and we never had any leaks. Previous flashing is still there but pushed against the wall and can still be seen above the plasterboard ceiling. Existing flashing shown here during construction
View media item 18126Should the new flashing have been inserted further into the wall (brick and stone wall behind the pebbledash) and a renderstop bead fitted as shown here
http://www.leadsheetassociation.org.uk/html/1398.html?

It might be a leak somewhere else, just want to get all angles covered .

cheers

Had a roofer up today and he reckons that the lead flashing has not been fitted correctly, only partially into the render.
His suggestion is to remove the pebbledash/render to 6 inches above the tiles, then step the flashing into the original wall ( with soakers????). I think that he also mentioned a cloak over the lead flashing then, and replace a strip of render above that. Thinking about it after I have not a clue what he means!!!
Lead alone will cost about £200-£250, he will come back to me with a proper price but I can't see it being cheap. The roof slopes about 10ft on one side and about 3 ft on the other side of the ridge.

Would this sound about right?

What size timbers have been used and at what span/centres?

They look awfully spindly to me.

Timbers are 4 x 2 with 600mm centres

Jackswan said:

Timbers are 4 x 2 with 600mm centres

Click to expand...

And the span? Is it 3m or so?

And the pitch?

noseall said:

Jackswan said:

Timbers are 4 x 2 with 600mm centres

Click to expand...

And the span? Is it 3m or so?

And the pitch?

Click to expand...

The span is just over 4 metres in the part that can be seen, pitch is about 20 degrees.
Just wondering if you are on to something here?

Just concerned about the amount of potential bounce or sag in the roof, particularly with snow, wind etc. It shouldn't effect a properly installed flashing though.

4"x 2"s will only span about 1.8m or less with those spacings.

noseall said:

Just concerned about the amount of potential bounce or sag in the roof, particularly with snow, wind etc. It shouldn't effect a properly installed flashing though.

4"x 2"s will only span about 1.8m or less with those spacings.

Click to expand...

You have me worried now!!!

But that picture does not show the final construction of the roof. There were purlins fitted in the longest span and the roof that you can see does only come about 7 foot out from the wall (it"s an "L" shaped room).

I did go on the roof with the roofer today and it does seem solid, there is no flex with at least an extra 30 stone walking across it.

But back to the flashing, should the top lip have extended into the house wall to do a proper job.

Does the way that the roofer intend carrying out the rectification sound right (with soakers on Marley Ludlow tiles)?

cheers

Hi. Rather than taking out existing flashing, why not cut a chase with a grinder a couple of inches above existing approx 35 mm deep and using 6" code 4 sheet lead fit a cover flashing over existing. Using lead sealant point the joint. Good Luck

justlead1 said:

Hi. Rather than taking out existing flashing, why not cut a chase with a grinder a couple of inches above existing approx 35 mm deep and using 6" code 4 sheet lead fit a cover flashing over existing. Using lead sealant point the joint. Good Luck

Click to expand...

I like this idea, just been up on the roof to see if it would work (must be mad as it is New Years Eve and freezing cold).

Noticed what could be a problem.

There are 3 lengths of flashing above where it is leaking and each one only has an overlap of a maximum of 20mm. Looking at the Lead association website, should be a minimum of 220mm. There is also the same mastic on the overlaps as there is where the flashing has been slotted into the rendering.

Just happened to measure the overlaps to where the leaks are below and they are directly above.

Think I will try a hosepipe on it tomorrow.

Justlead is right a good idea ...and d-I-y able . As to the short overlap, if it is well stuck with mastic all along the lap , it should be ok. Not Best Practice, but OK

I sprayed water over the wall with a hosepipe this morning and it only leaks when the water is concentrated on a small area just above where the knot can be seen on the timber to the right of the picture (a couple of inches to the right of the overlap in the original flashing). The strange thing is the leak is on the outside of the render when viewed from below rather than behind it. The pebbledash/ render does sound hollow when tapped above at that point (sounds as though it is a very thin coat of pebbledash/render) but no cracks.

I did like the idea that justlead gave and will mention it to the roofer when he comes back with a price as I think that the way that he is going about it does not seem quite right (could be a way of making extra money).

Any suggestions of which way I should deal with the builder who constructed the roof as the flashing does not seem to have been fitted correctly?