Concrete Shed roof leaking

It's exactly the same as my shed(s) actually two, the smallest one was a coal shed when built but now houses garden tools, while the large one has electricity and a freezer.

I cured mine and a few others around here with thompson's 10 year roof seal, it's water based and can be rolled on, it covers 1m2 per half litre and mine was a 5L bucket and I got two coats out of it although it never leaked after the first one. Make sure you go about a foot past the centre line of the roof otherwise the hairline cracks that run across both rooves will allow water through

It does sound exactly the same- the shed is, as you say, 2 sheds really- and one was the coal shed.

She has had someone 'paint some stuff on' before now, but that seems to have not worked, whether it was the stuff you tried, I can't say :-/

Yes its the freezing water during the winter that seems to do the damage. There is one not far from me like that. Brian

Synthaprufe (made by Ruberoid, ISTR) is the stuff used to waterproof concrete bases for serious radio masts on hilltops etc.

In message , Frank Erskine writes

However IKO say the membrane should not be exposed to UV light so it would be no good for such an application unless protected by a further covering.

Do the existing flaking bits of the previous coating need to be removed before applying the new sealer? If so, what's the best way of doing so?

I would slap a layer of torch on felt over it.. The 4mm heavy duty modified bitumen cap sheet with mineral finish looks ok and is very tough. A 10x1m roll is about £40, and you need a hefty blowtorch.