After you have completed a few walls and refined your plastering technique your speed rapidly increases.
Even then big areas can pose problems (as can massive areas for an experienced plasterer), but do not mean they cannot be undertaken – just a little more planning is required.
Controlling the suction will ensure you get maximum working time, but for very large areas it may be necessary to either:
Join the plaster
Use the merging technique and split the wall up into sections and completing the whole area (ceiling to floor of each section). Advancing each section a stage at a time – means that you have a series of wet edges. If one section is only one stage behind the other then rather than having a definite join the two sections will easily merge.
The techniques explained
Joining Technique (brief)
Failing that you can always try joining the plaster. Before plaster sets on the first section cut it back to give a definite edge and always make sure it is damped down with water. Then when applying plaster to the 2nd section spend time to ensure you avoid getting any plaster on the first section that is finished. Always keep this clean by scraping and cleaning with a brush any plaster that mistakenly gets applied. Keep the plaster on the new section flat and never thicker than what you are joining up to. Never lose sight of the edge otherwise before you know it you may be applying plaster on top of the previous section and bumps can develop.
Be prepared to spend a bit of time on the join!
It is hard to explain, so until I get time to do a video, I have included 3 explanations below - 2 merging techniques (trying to explain exactly the same thing) and 1 joining technique. Hopefully one will make sense.
Merging Explanation 1
By mixing up the skim plaster in different batches means the different setting times can be used to your advantage...
One example of using this method is (the sections can be as big or as small as you can cope with)....
1. mix up 1 batch – enough to 1st coat the 1st section (takes maybe 10 or 15 minutes?)
2. mix up another batch – enough to 1st coat the 2nd section (this batch will set 15 minutes behind the first section)
3. flatten off the 1st section
4. mix up another batch – enough to 2nd coat the 1st section and 1st the 3rd (The setting time of this plaster will now be possibly 30 minutes after the first batch)
5. then 2nd coat the 2nd section and 1st coat the 4th
6. stage 4 (1st trowel (fill in holes)) on section 1 and 2nd coat the 3rd
7. stage 4 on the 2nd section, stage 5 on the 1st section etc
So essentially by mixing up in different batches you are buying yourself extra setting time.
It can get a bit confusing as to remember exactly where you are but the situation will arise where on a very large wall the following stages will be taking place....
and you will have a series of wet edges hat you keep advancing down the wall.
If each section is only a stage or so behind then it will be possible to merge all edges in.
Merging Explanation 2
Divide the wall up into manageable sections so that it is not all setting at the same rate but you have a series of wet edges that you keep moving down the wall.
For example splitting the wall into 3 sections.
Apply a 1st coat to section 1. If for example this has taken 15 minutes then the next batch you mix up to 1st coat the 2nd section will be 15 minutes setting time behind the 1st section.
Then flatten off the 1st section and apply a 2nd coat. Then mix up a bit more plaster to 1st coat the 3rd section and 2nd coat the 2nd section.
You are buying extra time by mixing the plaster in different batches and advancing each section one stage at a time but never spending too long on any one section. Eventually you may have completed stage 5 on section 1, stage 4 on section 2 and stage 3 on section 3, each section or join is only 1 stage different to the next so the plaster merges in.
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