# Forum Home Renovation Plastering  Plastering/Skim coating interior rendered walls

## Bart

Hi Guys
I have never skim coated rendered walls before so wondering how hard it is
Firstly what plaster do I use, is it the same as Gyprock plaster??
And is it something that anyone can learn with some practice? Perhaps I shouldpractice on a wall which will be covered by a wardrobe or linen cupboard incaseI balls it up??
What trowel do I use?
I saw this guy and he makes it look very easy but Im sure as hell its not.  Skim coating a plaster wall like a pro - YouTube  Plastering a wall ( thin layer ) - YouTube SKIMMING A WALL part 2 - YouTube

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## Bart

Anyone?
Should i leave it to the experts?

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## an3_bolt

Looks like nobody knows or has not come past yet...... 
.....my help may not be very good - have done a few repairs. 
Watched the renders do the back addition to our house......and copied their style to do some rendering and white setting over 2 doorways that i bricked in and some large failed render areas and rewindowing(although a lot more slowly). The white set is a mix of gypsum and lime. (broral hardwall). In my case i used lime putty as i had it handy but the renders used bagged hydrated lime. One key componenent appears to be that it was placed onto 1 day old render that had not dried, in order to stop the white set from drying out too quickly and failing. 
I have had some other areas where i moved powerpoints off the skirting and up onto the walls. The repairs were made with a cement render. Topping and feathering in i used initially the same white set. I did have some failures i believe because of excess suction and drying too quickly. In any case for smaller repairs, i have settled on cornice cement. Interestly, i had a quick chat to one of the other dads at school who is a pro plasterer, he advised that he skims walls in cornice cement. However, i would be quite hesitant to do a whole wall in cornice cement as i do not work fast enough for that. 
Perhaps if the render that you are skimming is good and straight, with a small hidden area, why not give it a go? Got to practice on something to learn. However if it is a highly visible area and of a larger area, without the practice it might be best to get a pro in for optimal results in a short time frame. 
Hopefully not steering you in the wrong direction - but also hoping one of the pro guys comes along and can advise on what they do. 
Cheers

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## Rod Dyson

> Anyone?
> Should i leave it to the experts?

  I don't do rendering or solid plastering so left the reply to someone else.  I usually use cornice adhesive for any skim coating I do.  But this is not great for large areas.  The hard plaster with lime added is the way to go.  I would do a smaller area first.  You need to work out just how quick it is setting off to see what you are capable of finshing off in one mix.  
Personally I would leave it to the experts.    
if I had a reasonable area of render to set coat, even I would get in a solid plasterer to do it.  It is a case of horses for courses for me.

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## Bart

Sounds like white set plaster is the way to go.So what trowel do i use? Wood trowel or steel

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## Rod Dyson

> Sounds like white set plaster is the way to go.So what trowel do i use? Wood trowel or steel

  Steel

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## Bart

Can you tell me what hard plaster? Brand, type?
Any particular lime? I have a couple of bags of lime i could use
Found this Hard Finish Plaster   

> I don't do rendering or solid plastering so left the reply to someone else. I usually use cornice adhesive for any skim coating I do. But this is not great for large areas. The hard plaster with lime added is the way to go. I would do a smaller area first. You need to work out just how quick it is setting off to see what you are capable of finshing off in one mix.  
> Personally I would leave it to the experts.   
> if I had a reasonable area of render to set coat, even I would get in a solid plasterer to do it. It is a case of horses for courses for me.

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## an3_bolt

Boral Hard Finish or Gyprock Harwall - should be the same stuff - gypsum. 
I used lime putty as i have a little stash of it handing for pointing and tuckpointing around the house. However there are instructions on the bag (well the hardwall one anyway as that is the one that I have used) that can use hydrated lime ( bag lime). if using hydrated lime - if it was me i would make sure it is a fresh bag - otherwise it will be partially carbonated and not be as strong as an end result. 
Please note that i have limited experience in white setting - just what I needed to do to cover fresh level render that i applied to 2 doorways, window area and several small areas. 
Lime does take a long time to cure - it cures by carbonation which in itself actually requires it to be kept slightly damp. With fresh 1 day old render I found it requred minimal misting and cured very nicely. If it is already render that has dried out - might need to seek pro advice on that one ie it could suck the moisture out too quickly, crack and fail. 
Trial and error on a small area is how i started. 
Good luck. 
Good luck!

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## Bart

I remember seeing someone on You Tube splashing water on the plaster and troweling it, i wonder if this is because of the render being too dry?   

> Boral Hard Finish or Gyprock Harwall - should be the same stuff - gypsum. 
> I used lime putty as i have a little stash of it handing for pointing and tuckpointing around the house. However there are instructions on the bag (well the hardwall one anyway as that is the one that I have used) that can use hydrated lime ( bag lime). if using hydrated lime - if it was me i would make sure it is a fresh bag - otherwise it will be partially carbonated and not be as strong as an end result. 
> Please note that i have limited experience in white setting - just what I needed to do to cover fresh level render that i applied to 2 doorways, window area and several small areas. 
> Lime does take a long time to cure - it cures by carbonation which in itself actually requires it to be kept slightly damp. With fresh 1 day old render I found it requred minimal misting and cured very nicely. If it is already render that has dried out - might need to seek pro advice on that one ie it could suck the moisture out too quickly, crack and fail. 
> Trial and error on a small area is how i started. 
> Good luck. 
> Good luck!

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## METRIX

Are they old walls with paint on them, or freshly rendered walls ?

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## Bart

Fresh render, completed about 2 months ago   

> Are they old walls with paint on them, or freshly rendered walls ?

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## PaleRider

Having done three rooms in the old bungalow and on the fourth and hardest now (see plastering 1920s bungalow thread) I have found that skimming and getting a really good finish is hard but doing it to a reasonable standard is not so hard. As others have also suggested, I use boral hardwall plaster in a mix with hydrated lime. The more lime the slower it is to set I think but more workable. More plaster means a harder finish but less time to work and can lead to lots of sanding later. Try a small area because it can set fairly quickly.  
Learning this from a tradie he said about 50:50 probably works but soak the lime in clean fresh water first for a while (minutes to half hour) and then add plaster. I have one of those mixing tools used with a cordless drill which is fantastic to do a bucketful and saves time and effort.  
Skimming a whole wall is probably not so hard but getting a good finish is one for the pros I reckon, but it's a challenge. Easy to end up with very uneven walls even in small areas. Fresh lime and plaster is best, used old lime once and got bubbles in the finish, not good. Moisture always has to be managed and best to skim day after setting the mortar I believe but if later than that I wet the mortar using not an old paint brush as seems popular but a spray bottle set to mist, gives an even coverage and is very easy to use. Has worked on previous rooms.  
I also found the quality of steel trow makes a difference, gotta have a good edge. That is my very amateur experience. Good luck.
Greg

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## METRIX

> Fresh render, completed about 2 months ago

  We use Boral Hardwall Plaster, if they are fresh rendered, sand the walls with 60-80 grit and a block, you need get rid of any excess sand left on the surface after rendering as this will end up in the mix on the trowel and make a smooth finish harder to achieve. 
Expect the paper to wear out quick as you are sanding render, but you will see the difference when applying the plaster.  
Use Lime Putty such as Blue Label Blue Label Lime Putty for lime mortars and plasters 
We mix in the following ratio, but you can scale this down until you get confident, just keep the same ratios 
10kg of Hardwall Plaster, 1 x 25 litre bag of lime putty, 5 Litres of clean water, make sure to mix in a clean container, and use an electric mixer to make it easier and more consistent. 
This should cover around 15 - 20 sqm with around 2-3mm coverage. 
This site explains the advantages of Lime Putty vs Powdered Lime  Lime Industries - The Lime Professionals - Perth Western Australia

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## Bart

Awesome info guys

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## Bart

Would brushing the render with a stiff brush be ok rather than sanding it?

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## METRIX

> Would brushing the render with a stiff brush be ok rather than sanding it?

  Brushing won't remove much, a quick going over with a block will help you achieve a better finish.
You don't have to sand the render off, just make it smooth with no loose particles.

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## an3_bolt

Bart, 
Are you winning the white set challenge?

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## Bart

I havent started yet but just got 2 bags of hard set plaster and 2 bags of Lime Putty. I will start off a small section first. Prob in a couple of weeks.  

> Bart, 
> Are you winning the white set challenge?

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## rodster

> Hi Guys
> I have never skim coated rendered walls before so wondering how hard it is
> Firstly what plaster do I use, is it the same as Gyprock plaster??
> And is it something that anyone can learn with some practice? Perhaps I shouldpractice on a wall which will be covered by a wardrobe or linen cupboard incaseI balls it up??
> What trowel do I use?
> I saw this guy and he makes it look very easy but Im sure as hell its not.  Skim coating a plaster wall like a pro - YouTube  Plastering a wall ( thin layer ) - YouTube SKIMMING A WALL part 2 - YouTube

  Hey Bart, which I'd picked this up sooner for you. I have skim coated my entire hosue over the previously rendered painted and textured walls. Not as hard as you might think, but takes alot of practice. So be prepared to spend some time placing multiple thin coats and sanding away rough spots. there will be mountains of dust. 
There are severl skim voating compounds ytou can buy from bunnings. If you look for topping coats from Gyprock will do. To save your sanity and back, get yourself tool up. You need knives of varying widths and a decent plaster trowel. Dont worry about a trough, go a plasters hawk. I foudn soemthignt he premixed topping compounds would become difficult to manage. you can add water....and when I say a small about I mean it. a Little goines a long way. It cannot be dripping, but should be thin enought to place a very thin layer of plaster over the wall.  
Remeber if you screw up you can always sane smooth and start again. One more thing, you'll need to paint with a sealer binder once finished. The powedery servcie will soak up too much fluide when trying to pain with water based paint and go crazy. So oil based sealer binder. Bunnings should have some.

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## Bart

Thanks for the tips, i havent started yet but all info is handy.
I bought hardwall plaster and Lime putty, i will start a small section and see how it goes
Thanks again   

> Hey Bart, which I'd picked this up sooner for you. I have skim coated my entire hosue over the previously rendered painted and textured walls. Not as hard as you might think, but takes alot of practice. So be prepared to spend some time placing multiple thin coats and sanding away rough spots. there will be mountains of dust. 
> There are severl skim voating compounds ytou can buy from bunnings. If you look for topping coats from Gyprock will do. To save your sanity and back, get yourself tool up. You need knives of varying widths and a decent plaster trowel. Dont worry about a trough, go a plasters hawk. I foudn soemthignt he premixed topping compounds would become difficult to manage. you can add water....and when I say a small about I mean it. a Little goines a long way. It cannot be dripping, but should be thin enought to place a very thin layer of plaster over the wall.  
> Remeber if you screw up you can always sane smooth and start again. One more thing, you'll need to paint with a sealer binder once finished. The powedery servcie will soak up too much fluide when trying to pain with water based paint and go crazy. So oil based sealer binder. Bunnings should have some.

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## METRIX

> There are severl skim voating compounds ytou can buy from bunnings. If you look for topping coats from Gyprock will do. .

  Go for the Hardwall Plaster / Lime option, off the shelf topping coats don't offer the strength (Impact Resistance) of Hardwall, it is designed specifically for this purpose.

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## Bart

No worries, thats what im using  

> Go for the Hardwall Plaster / Lime option, off the shelf topping coats don't offer the strength (Impact Resistance) of Hardwall, it is designed specifically for this purpose.

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## Bart

Im getting closer to using this stuff so I want to ask, how much time do i have until the plaster dries and since the lime putty has alot of water in it do i still need to add 5 litres of water? (As written here)   

> We use Boral Hardwall Plaster, if they are fresh rendered, sand the walls with 60-80 grit and a block, you need get rid of any excess sand left on the surface after rendering as this will end up in the mix on the trowel and make a smooth finish harder to achieve. 
> Expect the paper to wear out quick as you are sanding render, but you will see the difference when applying the plaster.  
> Use Lime Putty such as Blue Label Blue Label Lime Putty for lime mortars and plasters 
> We mix in the following ratio, but you can scale this down until you get confident, just keep the same ratios 
> 10kg of Hardwall Plaster, 1 x 25 litre bag of lime putty, 5 Litres of clean water, make sure to mix in a clean container, and use an electric mixer to make it easier and more consistent. 
> This should cover around 15 - 20 sqm with around 2-3mm coverage. 
> This site explains the advantages of Lime Putty vs Powdered Lime  Lime Industries - The Lime Professionals - Perth Western Australia

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