When to use a plasterers float?

[John Rumm]

I thought tonight would be a good time to teach myself skim plastering (onto plasterboard). So as to make the challenge a bit more interesting I thought I would start off on a nice easy project like a ceiling! (albeit a small one in a new shower room (about 3.5 sq m in total).

So as per various guides posted to this very forum in the past, I mixed up half a bucket of multi finish plaster, with a "whipped cream" consistency. Slapped it on the ceiling with a conventional metal float/trowel i.e, something like:

it smooth ish and then went and had dinner. Came back and gave it a bit of a polish using the same trowel and the occasional splash of water. So far the result don't look to bad.

Then it occurred to me I have one of these poly floats, like:-

I managed to get a reasonable result without it, exactly when in the plastering process should it be used? and how?

[Dave Jones]

You only use a float for rendering ie sand and cement mix

[John Rumm]

So why do they call it a plasteres float, and the likes of Screwfix etc list it in the plastering tools section?

[Dave Jones]

Last time I checked, plasterers still render the outside of buildings and in some cases as a base coat inside!

Dave

[Anna Kettle]

Cos rendering is a subsection of plastering which is the general word to describe the trade. Floats can be used for the finish of exterior work in lime plaster too and there are eminent limeys out there who consider that 'rendering' is a verboten word when referring to lime plaster

Anna ~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[StealthUK]

I use it on the plaster bonding coat.

[Michael Mcneil]

You can use whatever material wherever you like and any variety of choices of applicators.

A steel float gives a finish on some small particle mixes that can be regarded as "polished" as the action is similar to a cabinet scraper.

Plastic or wooden floats give a better rubbed finish. There is nothing to stop you using them on mixes designed to give fine finishes. The finish will not be so highly polished though.

(I think.)

[G&M]

consistency.

Okay - when should you use one of those sponge 'floats' ?

[Dave Jones]

The sponge floats that you can get are usually used only for one coat plaster and such like, but I don't believe he has one of those!

Dave

[G&M]

interesting

No but I have and whenever I use it I always seem to make matters worse when used on the final coat. This thread made me wonder if it was the right tool anyway

[John Rumm]

Nope, no sponge float, only steel and the foam one.

I just wanted to check there was not some overriding reason why I should be using the foam one. Having had a look at the results in the cold light of day, I seem to have done OK with just the steel one. So I will carry on with that. Only another 48 plasterboards worth to do!

Does anyone recommend grinding the edge of a new steel float to take the sharpness off it? What about rounding the corners?

[Michael Mcneil]

That's because they are used as grouting applicators for ceramic tiles.

You can make one by sticking a mouse mat on a wooden float. It just gives the stuff a little bit more squeeze as it crosses the gaps and leaves almost nothing on the finished surface.

Sponged finished rendering is just a final finish given to walls while the rendering is still wet. A quicker and less demanding finish than a rubbed float finish which is a lot of hard work when the rendering has stood over night. You use a wooden float trowel and lots of water and elbow grease to give a finish that does not need painting to hide blemishes.

(Yes, right!)

[Andrew Gabriel]

Absolutely -- a plasterer hates using a brand new trowel. Traditionally, he would give a brand new trowel to a renderer for a few weeks, where the sand and cement usage would quickly polish up the edges and take off the sharp corners, and get the spring into the steel. These are all missing from a new trowel.

To polish the edge, find a spare house brick with a good flat face. You polish the edge by trying to saw through the brick with the trowel edge, whilst holding the trowel at various angles. You can also use this to polish small nicks out of the polishing edge.

If you are looking to buy a trowel, search for an old one in the shed, car boot sale, etc. Providing the edges are not damaged beyond polishing up as above, you will probably find it very much easier to use than a new trowel, which will have sharp edges and lack of spring until it's been worked in.

[Dave Jones]

ah I see, I sometimes use a sponge when polishing instead of a water brush, never tried a sponge float though.

[G&M]

Wickes sell it. But I always end up making the surface rather undulating so I've given up and have to rely on a quick sand which I know isn't right but at least gives the result I am after.

That said when I bought a brand new house in 1988, I had to sand every wall that a professional plasterer had done as it was almost as bad as my handiwork.