Here is Sean Adcock's latest news from Opus 40. "The end is in sight" he says
" Well the Canadians arrived and the scaffolding went up and so did the wall. A fair few beers went down and Doug Bell talked a lot. It was memorable, a fun time. Menno, Andre, Rich Mino (a waller local to the project) and Doug can be seen on the shiny new scaffold. Even more tie stones went in and then they left and Evan Oxland on ‘sabbatical’ in Philadelphia joined us ...and the rain came down but even so more wall went up.
Evan left and more ties went in, or in one case almost went in as my tape measure malfunctioned (it could not possibly have been my fault) and the monster needed stone surgeon Tomas Lipps to perform an emergency end-ectomy before it would fit into the hole in the back. Local waller Charlie Groeters bravely holding his half of the ‘bull-set’... chisel like sledge hammers used for accurate breaking off of lumps of rock. The end is literally in sight as we can now see the wall top level from one end of the scaffold. At the other end we still have around 5 feet to go as the terrace behind the wall has a couple of levels.
This wall is so high and our stone so similarly sized (normally 2-4 inch beds) we haven’t bothered with grading (reduction of stone size with height). It makes little structural difference here except for using thinner (1 inch stone) and/or thinner shims (very thin stones used to get over steps) and plates (similar to shims but thicker and a bit mire structural). Harvey Fite the original builder used many, but in a tall wall there is a great danger that these thin stones will crack or even disintegrate with the pressure of wall above them, weakening or even destabilising the structure, so their use has been almost entirely eliminated whilst the overall use of stone of an inch thickness has been greatly reduced. Such stones tend to crack where there are joints below them as pressure points can easily develop there, and so even if they cross the joint a ‘running joint’ can develop. It all adds up to potential movement and everything is geared to reducing that even if we cannot prevent it. We certainly do not want to encourage it. One problem at times has been getting people to remember when trying to sneak a shim or plate past me, that even though the wall might be at chest height for them there is still perhaps six feet or more wall to go and so compared to their normal walls they might as well be putting that thin stone right in the foundation, something (I trust) they would never do. As we near the top the plate monitoring will relax a little, and stone size will decrease, however there will still be little tolerance of the shim"