We ask you to bear in mind that timber is a natural product that needs care and maintenance and that it is subject to naturally occurring changes, which we have no control over. Both temperature and humidity can result in some movement to both the timber and the roof coverings. A good quality, durable polyester roofing felt is supplied on all of our buildings. There may be some movement or rippling after installation, this is mainly due to the fluctuation in temperatures. This is beyond our control and is not detrimental to the building or the roofing felt in any way and should settle down after a short period of time.