Mending Broken Roof Tile

My roofing tiles are Redland plain concrete 10.1/2" x 6.1/2".
I have found a broken tile that has snapped horizontally in half. Unfortunately, the tile is adjacent to valley tiles, twice nailed and only two rows down from the cement bedded ridge tiles. Consequently there's no chance of removing its top half and fitting a new tile unless I first remove the ridge tiles, which I don't want to do.
My best option is to cement/glue the broken bottom half of the tile back in place.
My question is; what is the best adhesive to use that is waterproof and will withstand slight movement and thermal cycling?
Cement mortar always seems to crack off over time.
A Google search suggested using RT-600, but I can't track it down in the UK.
Any recommendations anyone?
TIA

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What about glueing something on the bottom of the tile, across the break, to keep the pieces together and prevent water going through? Some sort of material that won't rot. If the glue can go through it, put a piece of polythene underneath so you don't inadvertently stick it to the tile underneath.
There are grab adhesives which will strongly bond masonary products, even when wet. I used to use Wickes Master "Forget Nails" Waterproof which was excellent, but they stopped doing that range. Someone can probably suggest a current product which works well.

Andrew Gabriel wrote:
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Miliput

Andrew Gabriel wrote:
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Yes, I did consider that. I thought of using either slate, or a piece of the thin cement fibre-board that used to be commonly used for soffits, although the cement fibre-board probably contained asbestos has since been banned.
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There doesn't seem to be a lot of choice. The material wouldn't want to be any more than 3 - 4mm thick. Maybe fibreglass sheet?
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I did considered using a piece of fine stainless steel mesh with polythene behind. The adhesive would pass through the mesh and bond well.
This still leaves the question of which adhesive to use. I wondered about an external tile adhesive such as would be used for tiling a swimming pool.
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I've just read the spec sheet for RT-600: DANGER! EXTREMELY FLAMMABLE. HARMFUL OR FATAL IF SWALLOWED. Contains Naphtha Solvents, Toluene and Ethanol. Keep from heat, sparks and flame. Vapors may ignite explosively. Extinguish all flames, burners, stoves, heaters and pilot lights and disconnect all electrical motors and appliances before use and until all vapors are gone. Prevent build up of vapors by opening all windows and doors to achieve cross-ventilation. May cause central nervous system effects including dizziness, headache or nausea. Contains n-Hexane which can cause peripheral polyneuropathy and central nerve damage. KEEP OUT OF REACH OF CHILDREN.
That more than enough to give our killjoy H&S Executive a fit of the vapours. I doubt I'll find it for sale in the UK!

On 09/09/2012 22:33, Andrew Gabriel wrote:
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Either Sicks Like Sh*t or Nail & Seal.

On 10/09/2012 08:19, The Medway Handyman wrote:
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It's going to have to be mighty UV resistant up there

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I don't understand the problem, you should be able to replace the tile in the same way as replacing a slate. See;
http://roofireland.com/replacing_a_broken_tile.htm
Mike

My roofing tiles are Redland plain concrete 10.1/2" x 6.1/2".
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I don't understand the problem, you should be able to replace the tile in the same way as replacing a slate. See;
http://roofireland.com/replacing_a_broken_tile.htm
Mike

I wrote:
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OK, I can answer my own question now. The best adhesive seems to be Araldite epoxy resin (original, slow-set Araldite, not the quick-set 10-minute version).
I deliberately snapped a spare roof tile in half and then glued it back together with Araldite. I left it for a week, and then tried to break it. The glued joint held firm. I then dropped the tile onto a concrete surface, whereupon it predictably shattered into many pieces. However, nowhere did it break along the glue line.
I have now glued my broken roof tile back in place, and the result seems perfect.
It's important that the tile is a simple break with matching edges to glue. Choose a hot, dry, sunny day - the Araldite needs 5-hours to set! Wire brush the broken edges to remove any loose material. Coat both edges with Araldite and push the two tile pieces together. I used a piece of plastic under the tile to prevent the adhesive from sticking to the tile beneath. I held the broken piece of tile in position with wire hooks and elastic bands, until the Araldite had set.
Providing the integrity of the glued joint isn't compromised by months of rain and thermal cycling, the job's a good un.

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Well described, I hope it has worked for you. May even encourage me to fix a couple of mine.

Interloper wrote:
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Milliput ( http://www.milliput.com/prod.htm ) is a coloured epoxy putty that resembles earthenware ceramic and does a similar job.
I've repaired the odd terracotta pot with that with similar results to those which you describe.