The works became a bit unstuck during the installation of the NBT Diffutherm insulation. The SVP, windows/sills and bespoke gutter were all located, sized and ordered based on a 200mm thick layer of insulation. All these items rely on the final finished surface of the render being where it should be within a tolerance of perhaps 10mm. The first issue was that the levelling coat, which was supposed to only take out any low points, became a full 20mm thick parge coat, which sured up the brickwork but moved the whole insulation/render out by 20mm. The second issue was that the brickwork wall was not plumb in any direction and the levelling coat had levelled locally but not across the whole facade so there were still high points, again causing the insulation/render to be a further 20mm further away form the wall than as designed in some locations. This meant that the carefully located SVP/Gutter and sills were now around 40mm closer to the render than designed and the sills especially must have a drip of at least 30 – 35mm for weathering. The solution was either to relocate/replace the SVP/gutter/sills or reduce the insulation by 40mm. In the end we manually removed 20mm form the 100mm Pavatherm base layer (the boards are glued in 20mm layers and this was tricky but not too bad) and swapped out the 100mm Diffutherm for 80mm which cuased a delay and was a real hassle. The answer is to bear this in mind when detailing, survey the facade and keep a close eye on the knock on effects of each stage! Example of a completed sill detail with the correct overhang:
