Using Thin Joint Clay Blocks

I’ve been meaning to try out thin joint clay blocks for a very long time, and finally we’ve used them on an extension! We used Weinerberger Porotherm 190mm blocks, with EPS insulation EWI system to give adequate U value.

I particularly like this Monoblock system, as opposed to UK industry standard cavity walls for a number of reasons:

  1. The walls go up very quickly. I mean, really quickly! The key to using the system is getting the first course laser level accurate. After that, the blocks fly up. Especially as they interlock and no perp joint is needed.
  2. I have a number of issues with cavity wall construction. It’s fiddly. All the things to deal with, which are by no means always done properly. Keeping the cavity clean. Cavity trays. Stepped cavity trays. Cavity closers. And using PIR insulation in the cavity, which is a magnet for causing interstitial condensation
  3. Better than timber frame construction in a damp climate such as we have in the South West, as timber frame relies on perfect detailing….
  4. I also think it’s easier to get airtightness detailing around window and door frames, and to avoid cold bridging when the frames are set forward into the external insulation.
  5. The insulation in this system is in the right place! That is, when you add external insulation, you hold the heat in the thermal mass of the clay blockwork. If you put insulation in a cavity, you get no benefit of thermal mass of external brick/blockwork

I know we love our brickwork in the UK. If we needed to show a brick façade on this system, we would use brick slips.

All in all, an excellent construction solution, which has been used on the continent for a long time. I know bricklayers are suspicious of this, but the truth is you need a top- notch bricklayer for the setting out! The reason you can get away with a 1mm bed joint is the blocks are machined accurately. It takes a bit of understanding of the principles involved, but it’s really very simple and effective to use.