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Repoint valley or make watertight using other materials

I had my roof retiled about 6 years ago. After about a year the pointing from one of the valleys fell out. I had it repointed but it fell out again after another year. I had it repointed again in October 2014 and it has fallen out again from under the roof tiles. I suspect it has never been done properly each of the 3 times it has been pointed. The firm that did the last repointing gave me a 10 year guarantee but I believe they are no longer trading so I can't get them back to repoint the valley.
I have 2 questions:
(i) If I have the valley repointed what is the best way of getting a long term guarantee for the job, e.g. personal guarantee from contractor, insurance backed guarantee.
(ii) As the pointing has fallen out 3 times, are there alternative materials to make the valley watertight, e.g. use lead or spray expandable foam under the tiles

3 Answers from MyBuilder Roofers

Best Answer

Hi,there are lots of reasons for the mortar to fall out,different pitch slopes,tiles etc.the way I wall the valleys up with new mortar is,using the right mixture of sand and cement,3 sand 1 cement with added pva,if you bed tiles in wet mortar and then leave to dry for at least 24 hours,You can then add second coat of mortar making sure you coat over first coat of mortar with ova first,I guarantee this will last for years,also I would like to add,use a very course sharp sand in your mix along with soft sand,This will help prevent mortar from cracking,hope this helps you best regards mike


Answered 2nd Oct 2017

Ive seen this happen many times, if its done correct then it would last 10 years. You could remove all the mortar and prime the tiles with PVA then re-point but i strip it out and do it again. What is lined in the vally? Lead or GRP fiberglass. Google dry valley!! No mortar. Good luck


Answered 6th Aug 2017

Repointing is basically a waste of time & money,what you should do is take out all the cement and re bed the tiles if done properly should last at least ten yrs.
The only material that will seal your valley is a good quality cement if you want it to leak by all means use expanding foam
Their must be an under lying reason for this happening continually but the only way is to remove all the cement & tiles down both sides of the valley then re bed them properly
Good luck Alex


Answered 3rd Aug 2017

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