New Flat Roof Felt Rippling

6 May 2008
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United Kingdom
I have just had a new extension built, I have had continual problems with the workmanship of the building company and yesterday we finally got to the snagging list. On inspection of the roof I noticed the felt has started to ripple (south facing flat roof) in a lot of places particularly the seam laps. Should I ask the builder to redo the entire roof or let him patch by slitting the ripples?

I suspect the problem is caused because they left the roof ply on the roof for two weeks while it rained. When they layed the felt they did not put new dry board on.

Many thanks in advance

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It sounds like the ply has delaminated. (was it WBP?) going over it in that condition is a bodge. Roofers roof, and builders build.

Roofers can build, but builders can't roof ;)
Xenon thanks for the reply, yes they used wbp, they did actually use a roofer to do the felting but they did it over the weekends over three weeks. The ply had been on for 2 weeks in the snow and rain before the roofer came and put the first bitumen felt on. Then came two weeks later to put the remaining layers of tourch on felt on. I had asked that the roof be painted in solar reflective paint but they have said they didn't do it because the felt is solar reflective anyway although it doesn't look very reflective to me is there a way of telling, a friend suggested it should have a slight sparkle to it?
Yup as been said def a case of wet ply, looks horrible when covered up and the only way to correct it unfortunately is to replace it.
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If the top layer is mineral finish, it does not need a solar coating. If not, it needs a coating. After its been redecked.
hi this some times happens on south faceing roofs as long as its not to bad does not leak and builder is willing to give waranty for at least 10 years
best practise is to nail the first layer.....the ripples may be caused by the felt being fixed in cold weather...usually cheap felt :( would help if poss
best practise is to nail the first layer

I've seen this referenced elsewhere and, personally, would like some clarification on this.

When laying the underlay felt layer onto the timber/board, is it best to nail it down or use felt adhesive (assuming that these are the only two options in this particular scenario).
the reason the first layer is nailed/spot bonded is to allow for movement and different rates of expansion and contraction between the decking and the felt,not such a problem now with high performance felts but cheaper felt forms raised ridges over time at the joints of the deck which then get damaged and allow water to penetrate.hope this helps :)

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