byrnesurfaces

The ceiling had a crack in it running down the centre, on inspection we found that 5 of the joists had come out of their slots allowing the ceiling to drop. So I drilled holes through each joist just above the laths, inserted a 10mm bolt to which I attached a garden wire tensioner, I attached the other end to a bracket bolted to the beam. Then I was very pleased to see that I could lift the ceiling the required amount just by turning the tensioners by hand a half turn each. This brought the ceiling up and secured it for the future. Now the decorator can fill the crack and repaint.  If this hadn’t been done gradually more strain and movement would have brought the ceiling down or at least damaged it beyond a simple two hour repair.

I am fed up with opening tubs of lime putty and finding that there is not the 15 litres I was expecting, I assume I am being charged for 15 litres so why am I not getting them all?

its not just the annoyance of being cheated but that I risk not having enough to complete the project.

This phenomenon is not restricted to one supplier and I assume its not deliberate but simply failure to properly supervise who ever is filling the tubs, I expect they shovel in the lime putty till the tub looks full and then in transit the putty settles down properly and hey presto the tub is half full. Why not fill the tubs on some scales or tamp the lime down properly because you wouldn’t get away with this in a bar – a pint has to be a pint so why can’t 15 litres be 15 litres and not somewhere between 10 and 15. 

There is a real danger that we are in some kind of quality creep in which lime tubs are not full and ready mixed mortars contain less lime – almost all ready made finishing plasters I have purchased have nowhere near enough lime putty in them – Fine sands need more lime – its all down to surface area: the finer the sand the greater the surface area hence silver sand requires to be mixed with at least as much lime putty – i.e 1:1 not 1:2.5 as with course stuff.  Come on, we need good quality materials and that means the correct amount of lime – adding stone dust instead to maintain workability is not good enough

The materials are expensive enough for goodness sake so lets have some good stuff.

This isn’t a case of workman blames tools – I know the materials are sometimes not good enough and so I have to adjust them to suite the project, I know I have to do that, many others don’t.

and now that’s off my chest I’ll pour myself my own short measure – a small dram of Laphroig quarter cask.

The keying of lime plasters and renders is I suppose, best done in a criss cross diamond pattern, you see it everywhere on old buildings, and this can be done with a scratcher made from sharpened laths or maybe a flat piece of wood with 4 or five triangular teeth cut into it. Or you could buy a metal wire scratcher as used by modern plasterers.

However, a lot of modern plasterers scratch their plasters and renders in a series of (often) wavy horizontal lines. Of course, there’s always the edge of the trowel brigade who, as if prompted by a latent instinct somewhere deep in their brains, make a few narrow criss cross token incisions.

On a visit to Dougga in northern Tunisia I found what I think is Roman keying, admittedly, it could be a decorative pattern but as the picture highlights it has been rendered over and so could be an example of local practice but as the city had at least an 800 year history refurbishments and alterations must have been widespread. And yet…

A scratcher made from stiff twigs a bit like a besom is extremely effective at both keying lime plasters and compacting. If the sticks are dragged horizontally across the render it both keys and compacts, used in a sweeping action it can be used to remove rogue high spots too. The keying pattern is very similar to the Dougga example, another method of compaction is to beat the render and I have read of this practice in connection with earth mortars and pargetting.

However, a bunch of twigs is surprisingly difficult too acquire, especially a bunch that doesn’t break up over the period of a day so I have started using a wire scratcher, and yes I often scratch in horizontal lines, and it too compacts the render.

I have even found a secondary use for it – it is good at teasing out the tangled horse hair I get from the stables.

As for Roman keying – I saw not one trace in either Pompeii or Herculaneum or even Chedworth Roman Villa. Has anyone seen any?

Theres a picture of whats claimed to be keyed daub from around AD63 but it looks more like a decoration to me as its a very regular decorative pattern. check it out:   http://xcavate.blogspot.co.uk/2012_05_01_archive.html

is this keying and is it done with twigs?

or is it a decorative pattern later rendered over?