Liquid rubber

I had our small balcony over our lounge bay leak some years ago and it's bene re-felted. The felt seems in good condition with no noticeable holes or tears in it however with the horrendous weather over the weekend the git has leaked!! I then found that rather than one flush piece of felt across the main part of the balcony there are two overlapping pieces and the mastic used to seal this overlap has cracked and caused the top layer to sit up and form a gap to the bottom layer. Now my first idea was just to get some waterproof sealant http://www.screwfix.com/prods/67521...s/No-Nonsense-Roof-Gutter-Sealant-Black-310ml and fill the gap which can be as cheap as £1.50 a tube from Screwfix (assume I just need No Nonsense Roof and Gutter sealant). Howver on having a look in the Screwfix catalogue I notice they do high performance Liquid Rubber, http://www.screwfix.com/search.do?_dyncharset=UTF-8&fh_search=36010-90 which comes very well reviewed.

Would the general advice just be to fill the gap in the sealant or would it be worth investing £20 in a tin of ISOFLEX liquid rubber and coat the entire roof. Also if using the liquid rubber do you need primer considering the roof is in good condition?

Thanks in advance for your help

An update, I used roof and gutter sealant to fix the gap which seems to have worked but I would still welcome anybody's views on the Liquid Rubber, I cannot believe I've had 49 views yet not one response lol!

The DIY repairs will only last a short while and the liquid rubber will only prolong it for another year or two.

Usually, once flat roofs leak, its time to rip off and start fresh.

Bene

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The annoying thing is the bitumen felt itself is in good condition just the join between the two overlapping bits wasn't. I've sealed this but then thought why not do liquid rubber over the top and doubly seal it. The mini flat roofs are a pain and the last fitter swore he'd never do one again

Image attached although not great picture you get the idea View media item 16995