This is a quick aside. A customer had a ceiling he needed me to plaster, he had already fitted the laths, sawn oak, he had fitted them really well with very good spacing, the job was simple the ceiling only 15 square metres – easy.
I got the first coat on on a Friday and on the Monday got a call that quite a lot had fallen off.
As the picture shows it hadn’t all fallen off but even so there were a few patches and it wasn’t immediately clear why. What was plain to see was that some of the laths had bent forcing the plaster off.
In the end we settled upon the likely cause – the laths had been tightly screwed rather than nailed and they were too tightly fixed to allow any stretching as they absorbed moisture from the lime. and so they had to bend.
If they had been nailed they would have split and and although adequately fixed would have been able to move just that little bit and wouldn’t have needed to bend.
If you think about it, each individual lath needn’t be fixed very securely or need be very strong as one lath isn’t doing much work and neither is one nail or screw in this case.