Roofing issues


When we bought his house almost 6 years ago several (20 or more) of the concrete roof slates were broken but still on the roof. Most were broken just above or just below the overlap point. Anyway as we hadn't sold the last house we could not afford to get a roofer in to do a proper fix so I glued them all back with a waterproof builders adhesive designed to stick to concrete.
The thing is they are still stuck back, in fact I have just stuck another one back that had slipped down from under the ridge.
What's the general opinion. Is my "temporary fix" storing up trouble or should I not worry about it as long as the roof does not leak, which it doesn't.
Whilst on the subject, the reason I noticed todays slipped slate was because I was up a ladder clearing out the gutters. Whilst at gutter level I could see just how heavy the moss covering on the rear elevation of the roof is getting. I have read in the past advise advocating both leaving it alone, as scraping it off does more harm than good, and that it must come off due to the harm the moss can cause.
What's your opinion? Scrape it off or leave it alone?
Mike
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Concrete roof *tiles* ?

Replacement tiles from a roofing merchant cost peanuts. Take one with you to match the pattern and colour. Current metric tiles are very slightly wider than older imperial ones. This doesn't usually stop you swapping the odd tile, but you may find you can't put many (or even more than one) next to each other in the same row.

It's not just visible leaks, but also it mustn't be letting water onto the roof timbers, even if it's not enough to see. Is the roof lined, and the lining in good condition? Does the lining continue right down into the gutters or onto an eaves tray, so any water running down it is routed clear of the building?

Leave it alone. If you don't want it, stretch a couple of lengths of copper wire along the roof just below the ridge. The minute amount of copper in the water run-off will slowly kill the moss and it will fall off over a few years (it's very sensitive to small amounts of metals). I saw a few houses recently which had had their roofs cleaned, probably as a result of leafeting, and they looked really terrible, so I suggest you avoid doing that.
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Andrew Gabriel
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writes:

They call them slates around here.

Its not the cost of the tiles/slates that bother me We did have to replace some as the broken off bits were missing so couldn't be glued back. The ripping of the nails that hold the old ones in place was a real PITA. I then had the problem of fixing the new ones and resorted to hooks.

The single story part of the house has felt under the tiles which is in good condition and can be seen above the gutters. The older two story main house has no felt under the slates. We have a big much used loft and I have inspected the whole roof area during heavy rain storms with absolutely no sign of water getting in anywhere

"leafeting"?
As our roof is hipped it would not be easy, I have read about a product called "Copperidge" which claims to stop moss but its B expensive. The moss doesn't bother me, it just looks a little unsightly.
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I'm not sure what you have. I've never come across concrete tiles being nailed on to normal sloping roofs, but maybe they are in particularly windy locations.

Should have said leafleting.

You just need a length of bare copper wire.
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Andrew Gabriel
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writes:

They are completely flat, like a slate and nailed in place with two nails through pre cast holes. Each one is about 50cm square and they a fitted in a double layer. The hips are finished with special shaped pieces that form part of the roof also nailed, not ridge tiles that are fixed over the slates and mortared into place. As in http://share.ovi.com/media/Muddymike.Housechanges/Muddymike.10548
Mike
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Muddymike wrote:

As long as the sarking (underfelt) is sound (and drops into the gutters at the end) then there shouldn't be any problems with leaks.

Personally I would leave it alone.
But If you really want to get shot of it, don't scrape or powerwash it off as it may (will) cause more problems than it's worth.
Simply get a thick piece of un-insulated copper wire and fix it at ridge level and let it weather there for a few years and the copper leachates will eventually kill-off most of the moss and algae.
To confirm this, have a wander around and look for a roof or two with the old copper flashings and you won't see any moss in the water flow under those, but plenty of it either side.
Cash
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The slates/tiles you refer to are "Hardrow concrete slates" There are three sizes 18"x18, 18 x 9" and the other size is used for eaves and top course. They are not normally nailed on but hung on with two nails pushed through the pre moulded holes in the slate. These slates are known for moss growth as they are laid with a gap of 1/4" between side laps. This gap gets block with general dirt and gravel from the face of the slate. The best way to clean the moss off is to scrap it out of the joint then wash off with a hosepipe, not a jet, as this will only push the dirt side ways. Start from the top and dont shoot the flow of water up the roof. Moss will always re a cure do to the gradual wearing away of concrete which intern refills the gap or silts up the rainwater guttering.
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Thanks Kipper, that's very enlightening. Any words of wisdom on replacing broken ones?
Mike
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I can't answer your question, but I can tell you that when it comes to roofing 'Kipper' (Keith) really does know what he's talking about. Be sure to follow any advice he gives you.
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Slide a trowel under the slates above the one you want to remove and gently ease the slate up until you can get a wedge of wood about 1" under each side of the two slates above so that you can lift out the one to be removed. If the slate is next to a hip start two slates away on the same row and remove them until you can slide the one to be removed side ways away from the hip. If its one under the ridge then more than likely you will have to take the ridge off.
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Kipper at sea wrote:

Don't get your roof water blasted. The moss has "roots" and after you kill it the remains of this vegetable material is available to hold water and not only attract further seeds/spores but also by swelling and contracting according to water and frost it weakens the top layer of the concrete, Result, further grief.
I was told this by an old plumber, backed up by an engineer and a carpenter - yes I caught them at a coffee and natter session in a workshop! They were talking about a firm that sends out junk mail advertising a roof cleaning service. At best the "untidy" roof will need repainting regularly from that time on, nice little earner: first ruin the surface of people's tile roofs and get paid for it, then you've got repeat business for the foreseeable future. Well, that's what they said and they're the kind of highly competent practical fellows who can do far more than just their own trades.
A L P
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