re-skimming over lime plaster

[suz]

Hi,

My father very kindly lime plastered a wall for us but he found it difficult and the result has "nibbles " in it (possibly sand?) and is a bit "scagged" in places. My questions are a) Is it possible to get a professional to re skim this to flatten it as it is in a victorian room so the oldy worldy look isn't quite so fitting! I've asked one who said no because as the top coat is now dry another skim wouldn't be able to bond to it but does anyone know any different? Also when my father applied the skim he found it really hard to knock up and to spread despite using a device on the end of a drill (he found it too stiff with a spade) and doing it for ages so he added water to get it to a consistency that he could spread. I suspect this is why it's a bit nibbly/sandy to the touch. He's used to plastering with gypsum so he's not a novice but this is his first foray into lime plastering! Any help gratefuly received as this was to be a nursery and the baby is now 7 months old and still has no bedroom!

 

[Gervase]

You should be able to put another coat on top without any serious problems. Scratch the surface well first to provide a key, and then make sure it's well dampened to kill the suction, and make sure the new top coat is press home hard and rubbed down haard again as it hardens.
A professional would happily reskim it for you but the trouble is s/he'd either want to do it in gypsum or charge you an arm and a leg for lime!

 

[suz]

Thanks Gervase - at least I know it's possible! The reason my Dad did it in the first place was to try to save us a few bob. It might be worth sending him on a course instead of forking out for a professional!!

 

[Gervase]

The courses run by the various lime centres are an excellent way of getting used to the material. Book yourself on one, too, and prepare to get bitten by the bug!

 

[BMcD]

As Gervase says, there should be no reason why it can't be re-skimmed. But to follow on from Gervases's good advice, use a mix of 3:2 lime putty:silver sand. Apply a tight coat from top to bottom across the wall. Then apply another coat slightly thicker in the opposite direction to the previous ie: side to side down the wall. When this has stiffened up scour the surface with a fine grain sponge float (grouting float), it's a similar process to foating up render in so far as you are consolidating the plaster giving strength and reducing the risk of cracking, it will take on a sandy appearance. Then apply a third coat the same as the first. When this has stiffened up slightly scour the surface as per the second coat. Immediately after scouring, trowel up with a wet brush (5" paint) from top to bottom across the wall, so one stroke with the wet brush up the wall is followed by the trowel up the wall and as part of the same movement when you get to the top of your reach, come down the wall with the trowel then back up troweling off the fat then clean the trowel. When this is done go in the opposite direction but only use a wet trowel another pass but in the oppsite direction again will realy close up the surface. Now with a semi-wet or half-dry brush, brush over the wall, first up and down then side to side then both ways diagonally and finally again up and down. This should give you a perfectly smooth finish.

Gervase wrote:

A professional would happily reskim it for you but the trouble is s/he'd either want to do it in gypsum or charge you an arm and a leg for lime!

Although this is undoubtedly true I see no good reason for it since it will still only be a days work to skim a wall regardless of what materials are used.

 

[Geoffrey]

I would definitely recommend a lime course at one of the centres.
I went on one last year and found it thouroughly helpful. It's useful just to be encouraged to have a go, and get past the almost mystical reverence that seems to be attached to lime in some quarters.
As Gervase has pointed out it is quite addictive. I have now repaired walls and ceilings in the house and rebuilt a collapsing garden wall - having previously had no experience of building or diy whatsoever.
It's not rocket science after all, and you'll always find lots of advice and encouragement on this forum.

 

[suz]

Thanks guys.

I did go on the SPAB homeowners course which did a bit on lime plastering but it was nearly 2 years ago and my notes are somewhat illegible! Is it reasonably easy to plaster a wall/ceiling relatively straight and smooth if you have no prior plastering experience?
I will definitely book myself on a course though!

 

[Gervase]

Plastering is one of those skills that it can take an afternoon to learn and a lifetime to master.
That said, some people find it easier than others - and it can be hugely satisfying. The best way to find out if it's for you is to go on a quick course at one of the lime centres, and then to practise on an old wall. As it's lime, if you're not happy, scrape it off, knock it up and use it again.
You'll know when you've got the technique right - it will look and feel right (a sort of Zen thing, I'm afraid) - and then you can move on to closing up and rubbing down and scratching for a second coat, and then to applying a second coat and...
...and you find that you can plaster.
Get a copy of Holmes and Watson's essential 'Building with Lime' for an extremely good primer in plastering, particularly how to get good plumb and square work using dots and screeds.

 

[suz]

Thanks Gervase. Well, we bought the house with the intention of spending years doing it up so I guess I'll have the time to perfect my plastering technique!