Lime Plaster Finish Coat

[chapel]

Hi Folks,

So, tomorrow i'm going to apply the finish coat to the walls in our stair well. It's a timber frame house, c.1620, so plastering in between the frame. Over the last few months i've gone down the 3 coat route, haired scratch coat, un-haired float coat, and now a 2:1 finish coat.

I'm a complete novice to this - its my first attempt and its gone ok so far. But i wonder whether any of you have top tips for the final coat. I've heard of putting two coats on straight after each other before sponging/brushing.

Any thoughts guys?

thanks, Paul

 

[johnandrew]

Hi Paul

From the Ty-Mawr course I attended I seem to remember we put on the top coat in two layers with time between each layer for the first to stiffen up a bit.

Also, Holmes and Wingate have the following to say in their book:

"For the very best work setting stuff for the third coat is applied in three successive layers, with time between for the work to 'steady-up'."

They go on to say that first layers should be laid on with a steel trowel as tightly as possible, the second layer with a wooden float in the opposite direction to the first and the final layer tightly with a steel trowel in the same direction as the first layer. Following this there is scouring and final 'trowelling-up'!

Maybe a simple two layer approach would be sufficient.

 

[chapel]

This is an old cottage so no need to fine finishing. I would think two coats is more than plenty (one more than plenty really).

So if i lay the first coat on, wait for it to stiffen up a bit, apply the second, wait for it to stiffen again, and then sponge to make it nice and remove ridges/level abit.

thanks, Paul

 

[chapel]

Just thought i'd update for those interested.

I used some excellent 3:2 lime plaster for the finish coat from Derek March (Brick and Lime Supplies in Maidstone, Kent). Really nice to work with which made it much easier for a first time lime plasterer. Just applied one coat in the end, although it was a thickish one (probably a couple of mm more than you're meant to). Waited for it to stiffen a little and then sponged to even it out. It looks great, very happy with it.

As a lime novice i would say that it is fairly easy to get a good result with a little bit of effort. A 3 coat process (scratch, float, finish) maybe a bit excessive for all requirements - think i'll go two next time in our 400 year cottage to save time and effort.

Top tips - if brick background make sure it's clean and dampened; and make sure the consistency of the plaster is right through knocking it up

Paul

 

[Penners]

That's interesting too know, thanks chapel. I have a couple of questions:

Did you scratch the float coat at all? If not, how did you finish it - a rough smoothing with a wooden float?

If you're going to use a two-coat process in future, will you scratch the undercoat?

 

[chapel]

Hi Penners,

Yes, i did scratch the float coat. I'd read about a using a devil-float, so after using a normal float to really compact and even out, I got a rectanguler piece of wood and put a nail through at each corner and used this in a figure of eight to give a fine key. To be honest this didnt quite go as planned or expected - the nails dragged out some of the bigger pieces, but i didnt mind too much as the open-surface this left in the odd place worked as a pretty good key!

In future i'd go 2:1 haired for the first coat onto brick. I'd then wipe it with a 'stick' (technical term) to knock off any large lumps, and then use a normal float to really compact it and flatten it out a bit. To finish i think i'd just drag a nail here, there, and everywhere for a key.

Certainly be interested to hear from anyone with more experience of a two coat approach.


Paul

 

[Penners]

Thanks for that, Paul.