Aaah, New Roof Leaking. Can't Understand Why!

[Timbo21]

Had a new roof put on and it's been leaking. Some of the joists are getting wet. One area is particularly bad and it has come through the ceiling in one corner.

Builder who put it on found a couple of cracks between ridge tiles and put some clear filler to see if that cured it. It hasn't!

Having a further look whilst it's been bucketing down. It looks like it's coming in where the tile is nailed to the joist. I have a loft velux window not far from that area, so I can pop my head out, and it looks perfect from the outside. The tiles are overlapped. You can't see the nail hole???!!

This is doing my head in. Any advice greatly appreciated.

The tiles are Redland 49's and the roof is felted.

 

[Alastairreid]

Sounds as though there's not enough cover on the tiles!

i cannot imagine a scenario where filler would be used on a new roof!

picture may give us a better idea.

 

[Timbo21]

Thanks for the reply alastair,

The filler is just to see if it cured it. So, what you are saying is they are perhaps not overlapping enough?


T

 

[Alastairreid]

The manufacturer/supplier of the slates or tiles will recommend the spacing up the roof between the battens (known as the 'gauge'), this usually varies according to the pitch of the roof and the degree of exposure. The spacing is in fact the same as the 'margin', which is the length of the slate or tile exposed. In some cases the manufacturer or supplier will specify the required overlap, typically it is around 75mm (3 inches), so the 'margin' and 'gauge' are just the overall length minus the overlap.

 

[Timbo21]

Just checked. The overlap is 3"

Basically, there are leaks all over the shop. You get 2-3 joists that are dry and then one that is wet. It's on the garden side of the roof, as well as the road side. I doubt anything can be seen from these pics, but here they are anyway.

Some pics

 

[Alastairreid]

The channels are broken off some of the tiles!! i count at least 6 from your pics.
they will need replaced.

 

[Timbo21]

Thanks Alastair,

Is that the underside of the tile link?

That's the problem then.

Thanks again,

Tim

 

[Alastairreid]

its the water channels where the tiles interlock!
you can see the spaces at the tail of the tiles where the channels are missing/snapped. this will correspond where the trusses are wet.

you should check there's no other damaged channels.

 

[Timbo21]

Thank you.

Should I get them to redo cement between ridge tile where a crack has formed, also?

 

[Alastairreid]

i would!
its a new roof, some of the tiles are not sitting very well either, makes them more prone to wind lift.

 

[Timbo21]

Been crawling round the loft. Found another wet joit on the other side of the valley, but can't see any broken channels

 

[Alastairreid]

its difficult if not impossible to locate broken water channels without physically going onto the roof and checking them.

is the upstand on the leadwork to the valley sufficient?

 

[SASroofer]

The ridges adjoining your neighbours roofs aren't laid on a thick enough bed of mortar either, with some ridges touching the tiles underneath.
This will be a weak spot and the movement in your roof will cause the mortar to crack and your ridge tiles to loosen.

 

[Timbo21]

The ridges adjoining your neighbours roofs aren't laid on a thick enough bed of mortar either, with some ridges touching the tiles underneath.
This will be a weak spot and the movement in your roof will cause the mortar to crack and your ridge tiles to loosen.

Do these guys know what they are doing?

Can I safely rely on them to fix this?

Additionally, there is a gap in the flashing on the corner of the chimney above the valley, which looks a bit open. I will post a pic tomorrow.

 

[^woody^]

Irrespective of what is happening with the tiles, the breather membrane should not be letting water into the roof space - it should be a barrier

Over time, those tiles will move and runners will crack, and the ridges will open up, and that is when you rely on the membrane to keep the water out

So its not just a case of sorting out the tiles, flashing or ridges