Plastering Preparation


Tools

Straight Edge – a good length is 1.8m high. A plasterer’s feather edge (aluminium)is ideal but a length of straight planed timber will suffice. Just make sure it is thick enough to not bend.

Board & Stand – plywood is ideal, or old worktops etc. can be used. This is a plasterer’s stand but a 'workmate' type bench, will do just as well.

Float – used to smooth out the backing coat after ruling off with straight edge.

Trowel – used to apply plaster. Any make of trowel can be used for backing coat but a good trowel is required for the finish coat. (see final section under Finish Coat) Finishing trowel.

Hawk – enables you to effectively load plaster onto your trowel

Bucket of Water & Brush – for keeping tools clean and soaking wall if needed.



Is the Wall High or Low suction?

Having an understanding of the following section is very important and can make the difference to obtaining good or bad results.


Soaking the wall with water if needed... Walls can be divided into two categories – high suction and low suction.

High suction backgrounds (porous) will suck the moisture from the plaster you apply very quickly. Plaster applied to a high suction wall will stick very well but may dry too fast - before you have a chance to flatten it. This suction can be controlled simply by the application of water. Water should either be sprayed or painted over the entire surface. As a general guide you know when you have controlled the suction as you will see the water running down the wall as no more can be absorbed. In some instances a hosepipe (where practical) can be very effective on walls with very high suction.

Low Suction backgrounds (slightly porous) will not suck the moisture out of the plaster. The plaster will only firm up due to it setting or by evaporation if working in hot temperatures. Therefore the latter stages of backing coat application may have to be carried out a matter of hours later. A background that provides no suction at all (painted surfaces etc.) must be properly prepared or the plaster will not stick. The use of a bonding agent such as PVA will need to be painted to the wall to ensure adhesion.

PVA should be diluted with water (follow instructions on can). A handful of sand mixed in with the PVA will provide a rougher texture when the PVA has dried – ensuring better adhesion. PVA can be purchased at any builders merchants or DIY store.

If PVA has been applied then it is still advisable to do the suction test. If this indicates the wall is still too dry then putting water on will have a limited effect. Another coat of PVA will be required. The more PVA that is applied the more the surface will be sealed resulting in the wall being less porous.




Suction Test

To find out if the wall you are about to plaster is too dry

1. Load your trowel with a small amount of plaster and apply anywhere on the wall to ensure you have an area of plaster of approx 50mm x 50mm

2. Leave on the wall for 2-3 minutes

3. Test plaster spot with fingers. If it is still as wet as when you put it on - then the wall is not high suction and will not need to be soaked. If however it has dried significantly in this period of time then you have a dry wall which needs soaking with water or PVA.


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The author cannot accept liability for the use of any of the materials or methods recommended in this manual or for any consequences arising out of their use. The author cannot guarantee the suitability of any recommendations made in this manual and shall not be under any legal liability of any kind in respect of or arising out of the content of this guide.