Thread: Gyprock flushing

Flat as possible then sand flatter

Run your hand over the joint until you can't feel any bump.

Even if it looks flat feeling is best.

The best thing you can do at this stage is get either a flat towell or 300mm joint knife and run it along the join to find any high spots.

Then using a smaller scraper scrape back any high spots until flat.

High spots are your biggest problem. It is impossible to fill a bump!!!

Low spots can have more fill added later if required. Once painted, over filled joins are very hard to fix, unless you are a very experienced tradesman.

Don't use a curved trowel, They are ok for experienced tradies that know what a flat join feels like off the trowel. But they will get the part timer into all sorts of bother.

Dont try to trowel over bumps in the basecoat, take the time to scrape it back. It is far too hard to sand.

If you top coat over a bump in the basecoat and try to sand it back later, you will find that you will just sand away the softer top coat, NOT THE HARDER BASE COAT, leaving you with a worse bump than when you started.

It is far better to do the scraping back when the base coat is still wet but set. The dryer it becomes the harder it is to scrape.

Once it is very dry you will need a very narrow scraper to scape back so it will bite into the hard surface.

When the join is still wet but set you can use an 8 or 6 inch scraper to scrape back, giving you a better feel for the high spots.

Don't worry even the experts (or at least those that are any good), will scrape back their work between coats.

Hope this helps.

By the way when feeling if a join is flat you need to sweep your hand over the joint very swiftly.

I always without exception take a 12 inch or 300mm joint knife and check the flatness of my joins. The reason I do that is, sometimes the board is manufactureed with a very slight shoulder on the recessed edge, using the joint knife will pick this up. Then I know exactly what I need to do to get the join flat.

Running your hand over will not always pick this up.

Another method is, after the top coat is dry, run the 300mm blade along the join very flat. High points will be exposed by a black mark left by the metal of the joint knife. (Plastic DIY tools are totally useless, don't even consider buying them even for the smallest job).

Also buy a metal internal angle tool for the internal corners. Failing that, for the handyman with a bit of time on their side, using a 4" scraper, second coat one side, let it set then coat the other side. This will stop you digging out the opposite side. Repeat the process with top coat.

Cheers Rod

Thanks Rod for that added info as there was a fair bit that I wish I had known when I did our first room here. The one thing that I did learn was exactly what you said about the plastic hand tools. I found them as good as two away sick. Quite often the plastic would break off leaving shards of it through my wy work. I'm going to have to go and buy a few decent tools for the next job.

Originally Posted by rod@plasterbrok

High spots are your biggest problem. It is impossible to fill a bump!!!

Low spots can have more fill added later if required. Once painted, over filled joins are very hard to fix, unless you are a very experienced tradesman.

Sorry to jump in here.
Rod, I'm guilty.
My first attempt at plastering was to reline our kitchen.
As I was relining the ceiling as well, I only had a worklight to illuminate the space.
After our sparky installed downlights, I was shocked to see that I had overfilled most of the joints.
How difficult is it to rectify?
It is painted.
I used multipurpose jointing compound.
Do I sand or scrape with a narrow scraper & fill imperfections with top coat?
Cheers.

The only way after it is painted really, is to trowell out the joins wider either side. Just use the same multi purpose or normal top coat.

Use a 12" blade and trowel out the full width of the blade either side of the join. When you sand start by sanding through the midddle and work out to the edges. This is very important, if you start at the edges you can sand off all the filling and have the same problem. By sanding the center first you will feel the high spots.

It is to hard to scrape or sand the painted surface.

Use the blade to see if it "rocks" on the join and if so give it another coat.

Hope it comes up ok. It is not really hard just take your time and do it in several applications if necessary. Any job comes up better with several thin coats building up, rather than one thick coat.

Cheers Rod

Bought myself a 300 metal trowel this morning after seeing my first attempt under some porta floods last night. Looked pretty good in the daytime but I wont' even let the missus look at it under lights. Cricky it's a bit ordinary. Hopefully nothing a heap of sanding and another top coat won't fix.
When mixing up the top coat, what consistency should be obtained. I also have a few small lumps coming through in it. Any ideas?

Ive always used the 'Soft peaks'' method, just liking whipping up egg whites in a blender, if you have ever done that.

Too runny and it will go everywhere... to thick and it's hard to work it smooth.

As for the lumps, try adding pwoder to water and mixing as you go, rather than adding to much powder at once. or adding water to powder.

Dean, your are right that powder should be added to the water. The only provision I would mention here is, that by adding powder then mixing then adding more powder, the mix will set quicker than normal.

The more plaster is mixed the quicker it will set. Cornice adhesive more than base coat.

The best mixing method is to add powder and let it soak for a minute. then add more powder (without mixing) until just about all water has gone. Let it soak a minute then stir adding small amouts of powder to thicken if needed, but before you have thoroughly mixed.

If you find you need to add powder after you have mixed up just expect a little less working time.

cheers Rod