Velux Window Installation Help


I have 3 velux roof windows (GGL style) installed in a newly built room. The roof is a standard wood rafter construction, felted and tiled. The felt and batterns were put on the roof before the velux went in. The velux flashing then went on, then the tiles. Around the edges of the velux installation, the roofing felt was tucked into the window aperture, then the velux fitted. Problem we have now is some water leakage around the edges of the velux. It is running down on the felt that was tucked in. Now I know firstly that if the tiling has been done properly there shouldn't be any leakage through onto the felt, that is one problem to sort out. However, if any water does get passed a tile onto the felt, then this should run down and of the felt to the bottom of the roof. The way the felt was tucked into the aperture does not seem right, especially above the Velux, as the felt does not overlap the top section of velux flashing, meaning if any water on the felt, runs down to the velux it goes under the velux flashing, then into the room. the builder assures me it is the correct installation and that once the leaks passed the tiles are sorted out then there will be no problem. the information on the velux site and the brochures I have are not very clear.So am I right in saying the roof felt, especially at the top of the velux should overlap outside/on top off the velux flashing?
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There are two ways to tackle this problem. The felt should be turn up the side of the timber frame at the sides and at the back. If this hasn't been done vapour will run in side the gap between the frame and the rafters. Take off the tiles around the frame, then the back gutter followed by the canopy then remove all the side channels, cover flashing strips and the front apron. You should be down to the frame and laths. Cut a strip of felt 8" wide long enough to go from the top of the frame 4" below the front. Fold the felt at felt 90 deg length ways with an up stand of about 2". Put the 2" up stand against the frame and lay the 6"on top of the tile lath, fix with staples or felt nail on the outer edge with 2" protruding above the top and bottom and , repeat this on the other side. Cut another strip of felt wide enough to go under the first horizontal lap and 3" up the back of the frame and 6" wider than the back of the frame. Lay this piece of felt over the lath that run between the frame and the first horizontal lap of felt, . tuck the piece of felt under the first horizontal felt joint making sure there is 3" over each end of the frame. Where the back over laps the side pieces cut in a diagonal direction both side and back gutter. LEAVING ABOUT 1/2" overhang. This enable the felt to be turned round the back and the back to be turn round the sides. Re fit the flashing kit and tiles.
Velux have purpose made vapour collars for the same. Code BFX
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Thanks for the info...the builder says it is not necessary to fit the collar BOX !Think we may have a disagreement here!
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When I was ordering my Velux from the merchants I asked for the flashing collar and the sales guy said he had never heard them. He rang Velux while I was there and was told the collar had to be fitted to validate the window warranty. They only cost about 15 anyway!
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