You will need to grind back the lifting patches and make sure that the edges left are roughed up to provide a good key. These are ususally done at the same time using an angle grinder or nose file. Make sure that the area is totaly dry. Once you are happy that the area is dry, wet out the area with resin try to make sure the wood is well coated and if there is any areas remain that have lifted from the roof force the resin under them. Now lay on the glass mat that you have cut to size so it over laps the the roughed up old grp and now using a brush or roller wet out the mat. You may need to start with mat that is cut to the size of the wood with no overlap and then increase the size of the patches as you lay them. Repeat this until you have got the patch leval with the rest of the old grp. Make sure there are no dry bits of mat or air bubbles, but you don't want the area swimming in resin. Once this has cured cover with top coat. You should be able to find more detailed instruction if you look about on the net. Try some of the material supply companies for instructions. Wear rubber gloves and paper overalls. When you have finished throw everything away responsibly as it will not be worth saving. Good luck...
John, September 2009
