Updated February 3rd, 2019
Defects in plastering can spoil all your creativity.
A home is a dream for most of us. We decorate our home in many ways. One of the ways is painting our home with our creativity.
Painting is normally done on the plastered surface. If the plaster quality is not good enough it can cause for many problems later.
As construction professionals, we need to take care of the quality in every step of construction.
When we plaster, we need to ensure the quality of it. So that we won’t face any problems later.
To ensure the quality of plaster, we need to know about the defects in plastering. If we know about the defects in plastering and the causes of them, we’ll be able to produce good quality plaster.
In this post, I’ll discuss the defects of plastering, their causes and how to fix them.
8 Common Defects in Plastering
We normally found the following defects in plaster.
1. Plaster Debonding
If the plaster tries to separate from the substrate, that is called Plaster debonding.
When debonding occurs, plaster is separated from the wall.
Now, you can imagine what will happen if debonding occurs in plaster!
This is a serious problem. We need to take preventive actions to solve this defect of plaster.
But before that, we need to know the causes of this defect.
Causes of Debonding
The following reasons are causes for plaster debonding –
- Excessively thick plaster layer
- A dusty and oily substrate
- Dry substrate
- Inadequate substrate preparation.
How to Prevent Debonding of Plaster
To prevent debonding of plaster, we need to take care of the following things during plastering.
- Remove dust from the substrate before plastering
- Prepare oily surface properly
- Allow substrate to reach correct moisture content.
- Use cement slurry coat on the substrate before plastering
- If necessary you should use bonding chemical
2. Lack of Hardness of Plastering Surface
How hard a plaster surface should be?
I didn’t find any specification anywhere that how hard a plaster surface should be. If you have any idea about this, please let me know in the comments below.
We normally use a key or a coin or nail to check the hardness of a plaster surface.
With a key, we just make a scratch on a plastered surface. If the scratch is left a deep sign on the surface then we think it as lack of hardness. Otherwise, it is a hard plaster.
Causes of Lack of Hardness
Followings are the main reasons for this defect of plastering.
- Using insufficient cement in the mortar.
- Having dust in the sand (more than 15% by mass passing through the 0.075mm sieve).
- Adding extra water to the mortar while it starts to dry. This is called re-tempering.
- If the plaster dries rapidly. It normally happens while plastering in the sunny or windy atmosphere.
- The use of a mix with poor water retention properties.
How to Get The Proper Hardness of Plaster
Take care of the following things while plastering to get the proper hardness of plaster.
- Maintain the right proportion of sand and cement in the mortar.
- Use washed sand
- Don’t add extra water after preparing the mortar
- Don’t allow the plastered surface to dry rapidly
- Use fresh drinking water in the mortar mix
3. Grinning in Plastering
Grinning is a condition of plastered surfaces where mortar joints of masonry blocks are visible through plaster.
Grinning can be a cause for plaster cracking in the long run.
Causes for Grinning
Grinning is mainly caused by the difference in suction between the mortar and the masonry blocks or bricks.
Raking out mortar joint is also a cause for grinning.
How to Fix This Defects in Plastering
The only solution to this defect is to apply an undercoat before plastering.
If gypsum based products are available in the mix of mortar then this defect happens in the plaster.
To fix this problem, you need to make sure gypsum based products aren’t available in the mortar mix.
5. Popping in Plastering
Popping is the formations of conical holes that break out of the plaster.
Causes of Popping
Due to the presence of contaminant particles such as seeds, dead burnt lime, and other organic materials, in the mix of mortar, this defect happens in plastering.
How to Fix This Defect
To prevent popping in plastering, you need to make sure no contaminant particles are present in the mortar mix.
6. Crazing in Plastering
If you examine a plastered surface, you may see a network of fine cracks, those are called crazing. They are usually very fine and shallow and formed in a hexagonal pattern. They don’t extend through the whole depth of the plaster.
Causes of Crazing
Followings are the causes of crazing.
- Using sands containing an excessive amount of dust
- Over trowelling high-cement contained mix (rich mix)
How to Fix This Defect
Crazing is not so harmful. It can be covered with paint.
7. Cracking in Plastering
There are many types of cracks appears in plastering – some are non-structural and some are structural.
Crazing is also a type of crack, which is non-structural.
We also find some other non-structural cracks. Such as map cracking, plastic shrinkage cracking, and drying shrinkage cracking, etc.
Structural cracks are mainly formed due to the movement of the structure. Such as, if a crack formed in the masonry wall, then a crack will also be formed on the plastered surface.
Causes of Cracking in Plaster
If structural cracks formed in the structure, only repairing plaster isn’t effective.
You should get some experts advice to repair the cracks of structure then you can repair plaster.
The causes for forming non-structural cracks are-
- If the high cement content mix is used for plastering.
- If the plaster dries too quickly.
- Using a sand in the mix which is badly graded and lacks fine materials (less than 5% by mass passing through the 0.075mm sieve)
- Not using masonry cement
How to Fix This Defect
You can fix most of the non-structural cracks easily using proprietary filler and painted over.
You can also use glass fiber tissue during painting.
You can repair most of the defects in plastering. More than that if you supervise the plastering process and make sure the quality materials are using in the plaster, you can prevent most of the defects.
Share Your Expertise
What kind of plastering defects you’ve faced recently? Please share in the comments below…