Help & Advice on How To Patch Plaster Blown, Damaged or Loose Plastering On Laths or Wooden Slats, Repair Plaster
How to Patch-up Broken, Loose or Blown Plastering. ( By a professional plasterer )
DIY ( Do it yourself ) plastering is a simple home repair technique which can easily be mastered within a relatively short amount of time.
This will help save a household budget a fair chunk of money as even the cheapest plasterer services cost a fortune.
Large holes created by blown or damaged plaster can be repaired and completed within a couple of hours, even by a novice.
Plastering Tools Required
Buckets - 1 to mix in, 1 for clean water.
Float / Trowel - To evenly spread the bonding and finishing plaster
Mixing Tool - To ensure a smooth mix ( cheap drill attachment is suitable )
Hawk - Not absolutely necessary, but worth the small cost for a better method of applying the plaster. Holds the plaster whilst working.
Water spray bottle - Important for a novice
Paint brush - about 3" in width
Wattle & Daub Damaged Plasterwork
This can be found in many older homes throughout the world. It is the most common type of plaster work that is used due to its easy sustainability and green values.
Remove any broken laths ( wooden slats ). You may need to chip away more plaster until you come across a beam to where the slats are fixed to. Or you can remove all the slats in the area and replace with a piece of plaster board.
When replacing the laths with either new laths or a piece of plasterboard, always ensure that the surface is countersunk below the existing finishing plaster.
This is so when applying the new plaster, it will finish flush with the original wall or ceiling. Plaster board, plaster or other materials are readily available from local plaster or plastering suppliers as well as general hardware stores.
Plaster Mixing Tool
Remove all loose plaster from around the hole. The plaster may be seem loose across a large area, especially if you tap it gently. This does not need to be removed, as when applying the bonding material, it will help with the adhesion. Just take away very loose pieces. This includes old plaster which is between the laths.
Coat the laths and approximately 6 inches around the hole with a solution of PVA and water ( ratio of mixture should be approximately 50/50 )
Mix an ample amount of bonding in one of the buckets. The consistency should not be runny but appear to be easily spreadable.
Put some bonding on the float / trowel and begin to force the bonding onto the laths. The bonding should be allowed to ooze between each of the lathes as this will form the adhesion.
Keep applying the bonding until the hole is covered over.
Using a large level or a straight edge that is longer than the hole itself, ensure that all of the bonding is recessed up to a depth of approximately 5 mm.
Remove any bonding that is proud or above the hole as you need to leave room for the coat of finishing plaster.
The bonding finish does not need to be smooth or totally level, but definitely below the surface of the original plastering.
Using clean water and a paint brush, smear 2 inches either side of the hole circumference with water. Then remove any more excess bonding. Give the finished bonding coat a light scratch to give a 'key' for the top coat of plaster.
Every plasterer loves skimming. It is the most rewarding part of his or her job. Skimming is the finishing coat of plaster. It can be applied after the bonding is slightly stiff ( usually about 4 - 5 hours after applying the bonding )
Mix some finishing plaster until very smooth with ABSOLUTELY NO LUMPS. Apply in the same fashion as the bonding, using long smooth strokes with the float / trowel. Ensure you apply this plaster over the edges of the hole.
Whilst skimming, skim past the edges of the hole. The plaster does not need to be smooth or perfectly even at this stage. Once the hole is covered with finishing plaster, allow to dry until it is soft to the touch and not gooey.
Apply a thinner second coat using the same batch of finishing plaster. This will be to fill all the dents left over from the first coat.
Whilst floating or troweling, the plaster will begin to come smooth. Allow the second coat to dry until slightly tacky.
Then, using the brush, apply some water around the edges of the hole again. Float or trowel over the plastered area, ensuring that any small indents are filled. Allow plaster to dry for approximately 5 minutes.
Perfect Plastering Tools
Using the spray bottle, lightly spray the new plaster. Trowel dry and repeat this process twice. Trowel drying is when a plasterer will float over the plaster and remove excess water. This will help with the finish.
Your wall should now be complete.
The finishing plaster may begin to 'blister' slightly in places during application of the finishing plaster. This is remedied by 'dry troweling', which is the same as 'wet troweling' but without the water.
Put some pressure on the float / trowel and go over the plaster several times until the plaster is smooth.
This is due to the amount of water sprayed or used. There is not problem here as it will be covered over when painted.
If you have any questions about plastering, leave your email address in the comments box below with your question and a professional plasterer will respond to you free of charge.
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