plastering

[shobo]

Hi. I recently went on a one day 'intro to lime' course which gave me the confidence to do my own lime pointing on hamstone (listed building, conservation area).
I now have some internal plastering repairs to do in the coming winter, much of it on laths. I will also need to restore some laths.
I am hoping I can acquire sufficient skills by doing a one day course dedicated to lime plastering, without doing a longer course on general (non-lime) plastering. .
Anyone out there been in that position ?
Regarding the restoration of laths, I will have to wing that a little bit. I would need to do a 3 - 5 day course to get instruction on that. YouTube might be good.

 

[Abi Cott]

I haven't used lime yet, but I can plaster with gypsum. I think it's a knack, either you've got it and can pretty much do it from day one, or you haven't and even a week long course will leave just muddling along.

I have the knack, my ex doesn't, it took him years of practice to achieve what I was doing in my first few attempts.

 

[TheSpid]

I've never plastered before and decided I wasn't going on a course as it was too far away and I have M.E. and wouldn't be able to do a full day etc. And I just got on with it. It was fairly easy to pick up [if you have an old house and don't want perfect walls]. There are LOADS of videos, plenty of advice and my brother had done some so I asked him for adivce - he came to visit to tell me how I was doing and said I didn't need him at all. Due to my M.E. I cant hold a full sized trowel so had a baby one that he laughed hysterically at but it did the job. I've just finished the top coat in the living room. And I'm mighty proud and think it looks really good. Our walls were ultra wobbly even with loads of dubbing out and I didn't want perfectly straight so we have embraced the curves. I even got curves on the window edges - my proudest moment. Yes, I could do it a little better, yes, I learnt as I went along, yes, it's not perfect - but hubby and I love it. Those sponge mark lines in pic three were eradicated this morning - I used the wrong sponge. Live and learn.

 

[TheForge]

Plastering on to lath, especially on ceilings is a world away from gypsum skimming. You need to apply plenty of pressure to force a good amount of plaster through the gaps to create good nibs else the whole lot will end up at your feet. Riven laths provide a much better key than dawn and the mix should be well haired/fibres c. 3.5-4kg per tonne.

 

[elizabeth]

Well done Spid ! Your plastering looks good. You have a nice natural shape to the window reveals. Did you make up the lime plaster or buy it pre-mixed? I’m tempted to have a go myself.

 

[TheSpid]

Well done Spid ! Your plastering looks good. You have a nice natural shape to the window reveals. Did you make up the lime plaster or buy it pre-mixed? I’m tempted to have a go myself.

Thank you - Still have room to improve.

it was a bit of both - some of the dubbing out we made our own as we had a bag of lime in the shed - the rest we got ready mixed and added our own hair to it -as we already had that too. Ready mixed still needs knocking up but it was easier than making our own.

 

[Gothichome]

Spid, taking on your own plastering, good for you. To my eye it looks great,

 

[88v8]

Embrace the curves, good phrase, I think it a shame when people aim for flat plaster and even start with strawboard or the like. Fine in C19, but not at all the vibe I want in a C17 house. Which is just as well as I don't at all have the knack of flat plastering.
Spid's looks just the ticket.

Few differences from gypsum:
First, the background must be damp. Thoroughly damp. And one needs to keep redamping as one works. I used a small pump-up sprayer.
Then, the plaster must be misted as it dries, I carried on misting every four hours for several days, that might have been ott but it limited the cracking which was important as I only applied one (thick) coat.
Finally, be careful not to get the plaster on your hands. No need to be fanatical about avoiding it, but my right thumb in particular seems to have got a good dose and the skin cracked right through in several places and took months to heal. In fact, as I look at it now, it still hasn't really healed after four months.

Ivor

 

[livias]

You don't need to go on a four day course to learn how to lath.

If the old laths are in good condition then leave them be. You might need to do some patchup work if there are loose flying ends. Useful things to do that are stainless fixings (nail gun or drill and screw) treated softwood (a supply of roofing batten is handy) and lath offcuts

New laths can be sawn or riven. Riven is stronger as it follows the grain, but sawn is much cheaper if you can get it directly from a friendly sawmill. Sawn is just fine so long as it is thick enough and it needs to be twice as thick as the equivalent riven lath. Lath is normally made from a good slow growing softwood like larch or chestnut

Laths need to be fixed with stainless fixings because you are probably fixing onto oak and the tannin in the oak will eventually rot normal steel. If you are doing a small and/or fiddly area then drill and screw. Larger areas are better done by nailing, but stainless nails are only available for a limited range of nail guns ie not for the cheap ones. Your choices are a Paslode 2nd fix nailer or an air nailer

The laths should be spaced as wide as your little finger ... which conveniently you have to hand
It is tempting when lathing a wall to end all the laths one above another, but dont do that for more than 400mm and then stagger the junction to avoid vertical cracks in the plaster
The laths need to be reasonably rigid so don't let them span much more than 600mm. Add extra treated softwood supports if necessary
Butt lath ends, don't overlap them
An alternative to lath which you can use on complex curves is stainless expanded metal mesh. It is horrible stuff to work with so wear kevlar gloves and be careful but there are some fiddly places where it is so much more useful than lath

Thats all I can think of for now ...

 

[TheForge]

Lath is normally made from a good slow growing softwood like larch or chestnut

Sweet chestnut is a hardwood. Softwood laths are inferior in durability and quality.

Laths need to be fixed with stainless fixings because you are probably fixing onto oak and the tannin in the oak will eventually rot normal steel.

The alkalinity of the lime plaster will also corrode ferrous metals although there is some evidence that passivisation occurs <pH12.5.

 

[shobo]

thanks all

 

[TheSpid]

Do wear gloves - ALL the time - it's cautic stuff - I got some under my nail (from a hole in my glove) and it lifted over half of it from the bed and it was blooming sore - I've had to wait for it to grow out. Wear a dust mask if mixing dry lime too - horrid stuff in you lungs. And eye protection too if you can - I wear glasses anyway so used those.