Roof repairs

[Lostgardensof]

The storm has revealed a few (5) leaks in our roof. I have made some temporary repairs using felt to the inside of the roof but the slate tiles seem to be attached to the wooden lats by really old looking mortar. The house is georgian with a lot of Early edwardian era pimping. Not sure how I can repair slipped tiles. Any advice? Will add a pic later today once I am in the loft again. Also slightly concerned that if I touch any the whole lots will come down.

 

[Cubist]

That sounds odd. Slate tiles are typically nailed to the battens and any mortar would only be used to close gaps at the ridge and edges of the roof. That said I have seen some roofs where mortar has been used under the leading edge of slates but I have always assumed this was to stop loose slates flapping around in heavy winds.

If the slates are loose either the nails have failed or the battens have rotted and released the nails and repairs can usually only be made from above.

 

[plasticpigeon]

I don't think the mortar is holding the slates on, they will be nailed. However sometimes "torching" mortar was put under the slates, to help stop the wind from getting under and lifting them. A few slipped tiles can be held in by taking the slate out, nailing a strip of lead called a tingle to the roofing batten under the slate, putting the slate on and then bending the lead strip over the front of the slate. The lead visible on the front edge should blend in with the slate colour. There are also newer Hall hooks that do the same thing. Hard to explain so here is a website with pictures.

http://www.handymanknowhow.co.uk/repairs/broken%20roof%20slate.htm

 

[CliffordPope]

If there is no underfelt to the slates then any slate roof can leak a bit in certain extreme circumstances.
Slates rely on water always running downhill, and the gaps between adjacent slates being covered by another slate that terminates lower down the roof, so water running off that slate cannot run back into the gap.

But water can always be blown uphill, especially if the wind funnels up a narrow gap. So if you have an exceptionally strong wind that just happens to be blowing directly up a roof, perhaps angled or funnelled by eddies from trees or chimneys, water can travel even a foot up a roof under a slate until it reaches a gap.
Part of the function of the weak mortar often seen on the inside of a slate roof is to stop draughts, and strong draughts can carry water spray.

 

[Lostgardensof]

After a closer look there seem to be nails under the bottoms of the tiles and then some mortar on the inside at the join.

 

[CliffordPope]

This might be useful:

http://www.roofconsult.co.uk/articles/tiling/tips75.htm

It explains the principles of preventing water ingress, and discusses roof pitch and exposure to wind, and the nail hole options.

The mortar isn't to fix the slates - it's to reduce draughts and to stop the slates rattling.

 

[Feltwell]

Looks like the remains of old lime torching to me as well - mortar on the bottom of roof slates or tiles, to stop water ingress as others have said - particularly snow I understand, which tends to gets blown around and up & under tiles / slates. Torching falls off eventually.

Slipped tiles can be repaired as PP states, but of course only from the outside. Ultimately a slate roof will get to the point where either the original nails have corroded so much that slipped slates are a constant problem, or the slate has weathered and is delaminating, at which point a full strip back of the roof is the only proper fix - at which stage a breathable roofing membrane should be fitted under the tiles & battens. This is the modern replacement for felt, and works very well. Torching is long since consigned to history, for good reason, it never worked that well.

 

[88v8]

Those tiles look pretty broken. Wonder if they've been taken off at some time.

It's also possible that the roof was originally laid with insufficient lap. Like my garage roof That conduces to leaking, avoided in my case by the breather membrane. Leaks can corrode the fixings, eventually exacerbating the problem. Each tile should overlap the one below and the one below that (double overlap). The required degree of overlap depends on the slope and the wind exposure.

Some roofs require a triple overlap.

It's a nuisance that roof deficiencies so often show up at the time of year when one is least able to deal with them.
Never mind !
Something to occupy you next year.

And there has been progress, not all bad... stainless nails, cheap as chips, and treated battens which may outlast the rest of the house.

Ivor

 

[CliffordPope]

Slipped tiles can be repaired as PP states, but of course only from the outside.

You can sometimes pull them back into position from inside, or pushing from outside with a long pole, and then securing with foam from inside. Builder's foam is very sticky and I think even needs moisture to stick better.
It's a bodge, but might serve for the moment.

 

[Feltwell]

And there has been progress, not all bad... stainless nails, cheap as chips, and treated battens which may outlast the rest of the house.

Indeed - copper nails work well also - and decent modern roofing membrane is remarkable stuff. Proctor Roofshield was our only roof covering for nearly 3 months before tiles went on, during a very wet autumn/winter. Very strong and almost impossible to tear, you could see straight through it from inside our attic, you could feel the wind blowing through it, but not a drop of water let through. So much better than felt.

 

[Lostgardensof]

Thanks guys. Ivor all the tiles have a rounded top, which makes it look like they are broken when they aren't.
I have felted the bits I can get to as a temporary solution and we will do the whole roof in a year or so once we have saved some money up.

The builders foam trick might work on the bits I couldnt felt. Very useful. Thanks guys