I rung Weber about this problem and their answer is basically it can't be done in their Weber Pral.m . The material is brittle and will crack with any movement which you will most likely get on a timber bay. This particular job was a typical 3 bed semi with double bay. There is the Webertherm Xl or XM material which is for insulation but will most likely be a different shade in colour to the Pral.m. There is also their polymer top scrape which might do the job but again may be a different shade and a different texture. so in this case none was acceptable. Their only suggestion which was off the record was to ply, breathable felt, expanded metal lathing, scratch coat of pral.m, let it stiffen up and then bed mesh into it and a second coat of pral.m making sure that both meshes and felt wrapped round onto the brickwork. But warn the customer that it may still crack if there is the slightest movement which is nothing new with Weber Mono anyway:RpS_scared:. Sorry for talking Weber talk but apart from some Primo I have only used Weber Monocouche.