Failed pointing inside tiled roof ('30s semi)

[James Amor]

Morning.

I've just been putting the Christmas decorations away in the roof and noticed that there were a few signs of water leakage on various bits of the roof joinery. Upon closer inspection it appears that the pointing on the underside of the tiles (no felt), which has been slowly falling away for years, has exposed quite a few small holes. The rubbish weather recently has been getting in through these small holes (biggest one is about 5mm dia.).

Am I ok just to repoint the underside of the tiles, or should I get a professional roofer to come and have a look? The tiling and woodwork all appears sound, it's just the pointing that looks to have failed.

Cheers, James

[mrcheerful]

pointing on the inside is probably just a previous bodge.

[meow2222]

Shouldnt normally be any pointing there. What sort of tiles, modern flattish concrete ones or old curved terracotta things? Sounds like someone else had a lot of roof trouble too.

As a bodge, you may get away with patching the mortar, but its nowt more than a bodge. I'd be asking why this was done with the roof in the first place. The usual reason is that the tiles/slates keep falling off, and its cheaper than reroofing.

NT

[Dave Plowman (News)]

A properly constructed tiled roof doesn't have pointing.

[Harry Bloomfield]

mrcheerful . submitted this idea :

No it was not a bodge, it was a standard method prior to the common use of roofing felt combined with a greater overlap on the tiles. They used a very weak mix of sand and cement for the pointing.

Actual holes, rather than just light getting in between the layers of tiles, would mean the tiles need to be looked at for damage.

[Bill Taylor]

A modern one won't, but one built before the second world war may well have. Ours, built c1930 has.

Bill

[James Amor]

I don't think tile damage is something to be concerned about, it's mainly where the corners of two tiles slightly overlap the top edge of the tile below - the corners of the tiles are not a perfect 90 so there is a gap. This accounts for 99% of the gaps - the pointing was previously covering these gaps up.

[James Amor]

The house is 1936 and having spoken to our neighbours, all the houses around here are built the same way.

[Grunff]

The 'pointing' is not there to stop water, rather to reduce draughts and minimise slate movement. It was most commonly done with lime mortar.

Our roof is the same, slates + lime mortar. Most of it has fallen away now, but the roof doesn't leak and there are no visible holes.

To answer your original question, no, you can't just plug up the holes with mortar. If you do that, water will still get through. The correct way of repairing this is to ensure no holes are present by allowing adequate tile overlaps.

If you only have a couple of holes, and the rof is otherwise watertight, you can use a bituminous roof repair compound to fill those holes, such as:

[James Amor]

Brilliant, exactly what I was looking for! Thanks.

[Dave Plowman (News)]

Ok - but most tiled roofs won't be that old.

[Harry Bloomfield]

James Amor formulated the question :

In that case I would not worry about it, our tiling seems to be a minimum of at least three thicknesses of tile overlap at every point of the roof. Most of our pointing has fallen off and we only get the slightest of water being blown in under extreme weather conditions. I don't think occaisional moisture is detrimental, only continual regular soaking.

[Harry Bloomfield]

on 08/01/2006, Dave Plowman (News) supposed :

That would depend upon the area, plus the availability/desireability/ cost of slate tiles. They have been using tiles for probably as long as they have been using bricks.

[Dave Plowman (News)]

Yes - but I meant that most '30s tiled roofs would have been replaced by now. Judging by what you see in London. Perhaps other areas had better tiles?

[Bill Taylor]

Well, ours, in Shropshire, is in a pretty good state. There are a few tile that have cracked, and one or two flaking ones, but the roof is still waterproof and sound, so there is no reason to replace it.

Being cynical, one could think that a combination of over zealous surveyors, over cautious building societys, over enthusiastic roofing contractors and owners who want a roof that looks brand new may perhaps have caused a few unneccesary roof replacements.

Bill

[Harry Bloomfield]

It happens that Bill Taylor formulated :

Ours too and I keep a small stock of tiles to hand for the day when it might need some replacements. These came from other neighbours who have been convinced to replace their roofs. The only tiles I have used so far, have been to replace ones >I< have damaged during the course of other work.

[Rob Morley]

ITYF it was usually lime mortar they used.

[Rob Morley]

It's called torching, and was a standard technique pre-WWII

[Rob Morley]

Most of the houses around here are still on their original 1930s tiles.

[Dave Plowman (News)]

None on mine.