Plaster Guy

Thanks Jim , you are on the ball. Nogs = blocking , Battens = furring , however you use plastic and what we are using is polystyrene 50mm x 20mm strips. I was on the phone today to the ploy supply company and he made a good point. Since we only drive home the nail heads or washers down 5-10mm below the surface of the ploy any shrinkage in the ploy of 15mm would make the heads of the washers poke out of the fibreglass mesh coat , BUT there is nothing at all showing in the join , just the dishing. SO knowing this one would think that it must be in the framing. We will need to ask the owner if we can put a straight edge on the wall inside to see if there is any plaster board cracking.... Not sure what you mean by dry Lumber and wet ? Is this kiln dried and tanalized ? Thanks Jim good answer.

Thanks guys for your answers, OK I'll try to describe how the system is put together. You have the studs at 600mm centers and nogs at 800mm centers. I've seen pics of the US framing and they tend to use full sheets of ply to cover the whole building. Not sure if you use the same method ? Anyway our framing ( apart from bracing sheets) does not use any ply at all. You install the building wrap and run 20mm x 50mm polystyrene battens down the 2 x 4 stud over the building wrap , thus creating that 20mm cavity. You then install one 100mm long batten on the nog either side of studs and along the bottom plate. Then fix a 40mm EPS sheet (1200mm x 2400mm) to the battens using a 22mm washer at 300mm centres. Then plaster away..... Since I wrote the last post we went over to a house I did 2 years ago and ,armed with a level, put it on the wall horizontally across the sheet join. In the middle there was a 15mm gap, decreasing to nothing 300mm either side of the join, ie: the join is dishing in 15 mm but as yet has not cracked the surface. The mystery is why is this only happening around the perimeter and not on the center studs or nogs ? We are heading back today to see if we can cut a sample out of the wall to see what's going on. The trade off is that the home owner gets his walls fixed up. We are even looking at the type of building wrap used. We have moved away from the old type of tar paper in 2002 and moved into wraps like tyvek. Is this part of the problem ? Who knows. I'll let you know is a couple of weeks what we find. Thanks to those who replied.

Hello, well down here in little New Zealand we repeated the same mistake you guys were in not that long ago. There's close to a 5 Billion dollar repair problem when it come leaky homes over here now. However the building industry has made us install a 20mm cavity to deal with any possible leaks behind the cladding. This is not the silver bullet but it's gone a long way. NOW here's our latest problem.... homes that we have plastered with EIFS are showing stress lines right around the perimeter of the 40mm sheets only three months after completion. Large walls look like a patchwork quilt. The shrinkage lines are very straight and are only 5-7 mm wide but can be up to 6mm deep. It only seems to be on the studs and nogs but not in the center of the sheet. This is a HUGE problem but no one has taken the suppliers to task YET. What's making this happen ??? Cheers, Plaster Guy.