Help! maybe I'm not cut out for plastering!

[Bitstreams]

Advice needed urgently..

I'm having the devils own job lime plastering. I'm replacing concrete tanking on a rubble-stone wall (with some brick bits) with a lime plaster. The main coats have gone on fairly well I think but I'm having a real problem getting a good finish with the top coat. The problem seems to be that the walls aren't flat - they're flatter than they were but there are undulations generally. In trying to get a smooth finish the ends of the plasterers trowl thing (you can tell I'm a beginner) cuts in and ruins the edges of the finish.

It's nowhere near as smooth and even as a gypsum plaster wall done by a professional plasterer.

I keep changing my mind from - "it's ok - it looks cottagy" to "time to ring a real plasterer and get it done properly".
I don't like the idea of the latter, because I'm supposed to be renovating this house, not just opening my chequebook and getting someone else to do it.

Advice please - this is supposed to be a 'plastering' weekend.

Simon

 

[Schoolmarm]

Well I am impressed :lol:


What are you using to finish? Should it be a cross grain wooden float thingy?

 

[Bitstreams]

'using to finish' ?? you see, I might be missing a complete step or three.. I have a plasterers polypropoline, yellow thing that I found in Wickes - it said it was for plastering. The surface of it is all rough. When I tried using it to smooth up the scratch coat it ripped the surface apart. So I stopped.

SImon

 

[Schoolmarm]

Well I haven't plastered but in anticipation of doing it my daughter bought a special wooden float with a smooth surface. I will see if I can find a link.

 

[Schoolmarm]

http://www.oldhousestore.co.uk/category/Brushes__Tools__Safety_Equipment___Ancillary_Products/Plastering_Tools


It is top right.

I bet every person with experience and the answers you need will be too busy to come on here today.

 

[Schoolmarm]

What about this video?

http://www.youtube.com/watch?v=AOxPsK6MZzA&feature=related

 

[Andrew Bodenham]

Simon,

That wall's looking pretty good - well done.

Finishing - depends a bit what sort of finish you want. In an old building it's often appropriate to have a 'smooth but not flat' finish, rather than the dead flat look of modern 'professional' plastering. Having said that, you want to avoid trowel marks as these look bad.

What mix are you using for your final coat, and how thickly are you applying it?

From recent experience I found that a final coat of 1 part lime putty to 1 part fine sand, applied about 3mm thick, gave a good result. Wet the background well. After trowelling it on and getting it fairly flat I worked over it with a wooden straightedge to rub off the high spots and see where it needed a bit more build up. At this stage you can go for dead flat I you like - I settled for gently undulating. Once the final coat had stiffened a bit (depends on how absorbent the background is) you can work over it with a wooden float. You can buy these, or knock one up from a bit of scrap wood. Ideally it would be hardwood, with a nice handle, but I made one from a bit of pine - as I was patching small areas it was about the size of a postcard. Rub over the surface, pressing quite hard - spray the surface with water if it's gone too stiff. The wood float will compact the finish, whilst knocking off high spots and blending in those annoying trowel marks and other imperfections. If you find any big hollows at this stage you can apply a bit more plaster with the wooden float and rub it in. The finish from the wooden float will be slightly rough - you can stop at this if you want a 'rustic' look. If you want a smooth, polished finish then you need to work over the surface again, this time with a steel float, spraying with more water and pressing hard with the float at about 10 - 20 degress to the surface i.e. only the edge making contact. Continue until a smooth surface is achieved - it will become quite polished if you really go at it.
Beware of building up the final coat too thick as cracking will occur. Slow drying can help to avoid this.

Hope this is of some help - I've developed my technique by trial and lots of error, and I hope that somebody with real expertise will be along shortly to share their experience and tips.

Don't give up! If the work in your picture is still fresh you could scrape back any bits you're really not happy with and re-work them. Lime plaster is very forgiving in this way.

 

[Bitstreams]

thanks for the long reply Andrew.

I haven't given up and pressed on with it this afternoon, plastering up to the ceiling.



The plaster I'm using is pre-mixed (I just add water) - the base coat is Baumit Hi-Q Basic and the top coat is Baumit Hi-Q Top - it's a lime based salt-retention plaster, recommended by NBT, so I don't have any scope to vary the mix. I am putting it on about 3mm thick and I've found this afternoon that I get a better result if I put it on in a couple of coats (wet on wet) with the second coat being very sloppy.

I'm not bothered about the flatness of it, but the trowel marks have been driving me mad - I will try your wooden float idea on the next wall. Having a smaller float sounds like a good idea.

thanks

Simon

 

[DaveBrigg]

I found that coming back to it an hour or two later, when it had hardened but not gone off completely, and rubbing out annoying marks with my finger worked quite well. Not sure that I should be admitting this though

 

[Schoolmarm]

Yes but does the Baumit behave like lime? I have googled but can't find what it is made of.

 

[Me!]

I've never used Baumit, but I've just found a page that says it consists of "Sand, lime, white cement and additives" -

http://translate.google.co.uk/trans...=6&ct=result&prev=/search?q=Baumit+Hi-Q&hl=en

With gypsum plaster, if you get the corners of the trowel gouging out grooves in the plaster, then you either need to make the surface flatter first by using a long straight-edge on the base coats before putting on the top coat, or if you are happy with a slightly undulating surface but don't want the grooves, then usually letting the top coat dry a bit more before finishing will help. Also, use a decent trowel with a nicely sprung blade. I'm only self-taught so there may be a way around this, but I absolutely cannot get a decent finish with a cheap DIY trowel, but I can with one of these -

http://www.screwfix.com/prods/69112...s/Marshalltown-Permashape-Finishing-Trowel-14

Finally, related to grooves, but really the opposite are tramlines which are left by excess plaster running off the corners of the trowel, and which can then make you keep going over the same bit too much. To avoid these, keep the blade edge clean by damp for each use. Each time you rub the blade over the surface, then lift it and wipe the edge with a very damp towel or large wet paintbrush.

This all specifically applies gypsum plaster, but as the stuff you are using contains "cement and additives" as well as lime, then maybe it behaves the same?

PS. How do people shorten url links to one word rather than the huge ones above?

 

[Flyfisher]

Like this: Screwfix Trowel

description

 

[MdB]

PS. How do people shorten url links to one word rather than the huge ones above?

If you copy and paste a long URL directly into the post, it gets automagically turned into a clickable link.

http://www.verylongurltosomethinginteresting.com

result: http://www.verylongurltosomethinginteresting.com

You can also put URL tags around the URL but it most cases this doesn't make any difference

[url]http://www.verylongurltosomethinginteresting.com[/url]

result: http://www.verylongurltosomethinginteresting.com

To make a link to a long URL appear short in the post, you have to modify the URL code as follows:

[url=http://www.verylongurltosomethinginteresting.com]Anythingyoulikehere[/url]

result: Anythingyoulikehere

So, in your post above, you can use the following code to shorten things down:

[url=http://translate.google.co.uk/translate?hl=en&sl=cs&u=http://www.m-servis.cz/admin/sklad/tl/tl_3105_hiq_top.pdf&ei=FPPFSYj2AYS2jAfouJWeCw&sa=X&oi=translate&resnum=6&ct=result&prev=/search%3Fq%3DBaumit%2BHi-Q%26hl%3Den]First Link[/url], [url=http://www.screwfix.com/prods/69112/Hand-Tools/Plastering-Tools/Trowels-Floats/Marshalltown-Permashape-Finishing-Trowel-14]Second Link[/url].

Result: First Link, Second Link.

 

[Gervase]

The problem is that Baumit doesn't behave like a real lime plaster. The cement in it means it 'goes off' much too quickly for the average DIYer; you've only got about 20 minutes to lay it on and then polish it off to get the finish you want.
One way around the problem is to dampen the background well first to kill suction, lay it on with a steel float, aiming to get as even a coat as you can but not worrying too much about trowel marks. Then you wait until it's just starting to go off, and start with a sponge float. You can get coarse and fine sponges - a fine would be ideal. Wet the float and then pull it across the lip of your bucket to get the excess water off, and then gently draw it across the surface in a circular motion. As the pores of the sponge fill up with plaster, rinse it out in the bucket and drag it across the lip again before carrying on.
You'll end up with a slightly sandy finish, but you won't have trowel marks and the surface will look even.

 

[FamilyWiggs]

Must admit - wasn't aware you could use a float to finish lime plaster. As Gervase points out - a sponge is a very useful finisher.

The lime plastering I have done, which isn't extensive - has involved using a round ended trowel to smoothe the final coat and then a damp sponge to finish it off. You get a slightly sandy undulating surface this way, which is what we wanted. The great thing about lime plast is that you have hours and often days to keep coming back and doing more to it, provided you keepwetting it.

 

[Stevis2007]

Must admit - wasn't aware you could use a float to finish lime plaster. As Gervase points out - a sponge is a very useful finisher.

A sponge isn't the best way to finish a lime plaster wall, as it tends to pull on the plaster too much.
The best way to finish is exactly as mentioned above, by using a metal float, just as the plaster is starting to go off.
If it goes off a little too quickly, then just re-wet it slightly using your average garden spray bottle with water in.

You will not get the same finish with Lime as you will with Gypsum, as it is completely different, as is the texture.

Hope this helps

 

[Gervase]

The problem is that Baumit isn't lime plaster, and it goes off extremely quickly. Thus, if you haven't got good trowel skills, a fine sponge float is probably the only way to achieve something near an even finish short of employing a plasterer.
With a true lime finishing plaster (1:1 silver sand and putty and absolutely no cement, white or otherwise) you can get a surface every bit as smooth, flat and dense as gypsum. Lay on the last coat double in alternating directions and then polish like b*ggery (with a bit of wetting) with a decent broken-in finishing trowel until it rings as you pull it off and you'll have a surface like polished marble. Look at the walls of the great Georgian and Victorian mansions - they're lime plaster. There's no magic involved, just craft. Even with 'cottage plaster' or coat-and-a-half work (using the same 3:1 coarse sand and putty mix throughout) you can achieve a good smooth finish. It just takes patience and a bit of judgement - start too soon and you lift too much lime to the surface and weaken the plaster; too late and you'll knacker yourself.
Lime plaster doesn't have to look like it was thrown onto the wall with a pair of Marigolds, and even in quite humble houses the plasterers took a pride in their work and made sure the finish was plumb and smooth in the best rooms - the parlour and the master bedroom particularly.
I confess to wincing inwardly sometimes when I see people proudly displaying their 'rustic finish' and priding themselves on its 'authenticity', while imagining the original builders silently spinning in their graves. We owe it to them, at least, to ensure that the work truly is as authentic as possible.

 

[Jon Maine]

Gervase is right we have some very smooth walls here with fine sand/putty lime finish. I see no reason to use other material or excuses for poor finish. Even the old plasters in the building may dished and bowed but had a good smooth finish.

As for trowels these are well worth using http://www.buildingforhealth.com/products.php?cat=324 I am unsure if you can get them in the UK yet.

Here is a picture of topcoat going on

 

[Gervase]

Those Japanese trowels do look rather funky, but I'm not a fan of the boat nose. Call it habit or call me a bluff old traditionalist, but I tend to use yer bog standard trowels. Almost any old trowel will do for laying on - Jewson's own brand or the £6 unbranded from your local farmer's co-op are equally good. For finishing, though, I like Tyzak or Marshalltown trowels, and lean towards Marshalltown because the rubber handles don't give me quite as many callousses. Marshalltown do a good range in spring steel or stainless steel; I particularly like their little 8x3 detail trowel, while the big stainless steel, pre-worn,'permashape' is an absolute beauty. To paraphrase the lager advert, it's probably the best plastering trowel in the world.
Tyzack are nice - and British - but not as widely available or in as many sizes as the US Marshalltown range (which is a shame). They do now do soft-handled trowels, but I've yet to try one.

 

[borischarlton]

I am a novice and am just about to do the last wall in my first whole room. Its funny as you can see the walls getting progressively better throughout, I now want to start the first one again. However I am going to leave it as a memento as to my learning about how to conserve the house the best I can. I have found that some tools are invaluable, those threshold trowels for getting behind pipes and other obstacles, both inside and outside corner trowels and a very small float that was needed for a narrow strip of ceiling. Most of my tools are silverline and all bought from ebay for less than £25. Those pump up garden sprayers are a whole lot better than than the basic ones that do not last and are less wearing. Although My walls are not flat they do have a solid finish with no trowel marks, I did not like the finish left by a sponge as it was rather sandy.
Rob