Can you damp proof without removing plaster?

There are many ways that damp can form in a property. This could be internal moisture from things like condensation or leaking pipes. It can also penetrate in from outside through building defects. This includes rising damp, which draws water directly from the ground beneath your property.

The type of damp you are suffering with will determine the course of action needed to fix your problem.

One question we often hear, is “can you damp proof without removing plaster?” The answer to this is yes. In most cases removing plaster is not required to treat damp.

Plaster removal is only needed when performing certain damp proofing jobs. These include certain methods to fix rising damp. As well as applying forms of tanking that will be plastered over.

On the other hand, something like condensation treatment, could be as simple as helping air circulate and extracting moisture.

There are also times you will repair damage after damp issues have been fixed. This may require you to re plaster. However, the removal and replacing of bad plaster is usually not a requirement to stop the damp. Instead it is a cosmetic treatment, that is performed afterwards to tidy up the mess damp has caused.

Re plastering for rising damp treatment

The main time plaster removal and replacement is required is during work to fix rising damp. This is required for a couple of reasons.

The main reason is that moisture and hygroscopic salts will be present in the existing plaster. These will have been extracted from the ground and travelled up through the masonry.

If you simply inject a chemical damp proof course and leave the original plaster, this moisture and salt will remain. This could mean that the wall still shows symptoms of rising damp, even after the issue has been fixed.

It is also worth noting, that chemical DPC usually needs injecting into the mortar bed. Even if the plaster is in good shape and replacing it is not essential, a small amount may need removing just to find the correct site for injection.

Re plastering for penetrating damp treatment

In most cases penetrating damp will not require re plastering to fix the actual issue.

As the name suggests the damp is penetrating in from outside. This means that a defect on the external of the property is allowing water to enter inside. Due to this the work required to fix the damp is usually done from outside.

This could include jobs such as:

• Repairing or replacing cracked and damaged bricks.
• Replacing old pointing
• Fixing issues with old damaged render or pebble dash. This could be patching small defects or completely replacing the external render.
• Re-applying external masonry paints or creams
• Fixing damp issues on the roof or chimney

Whilst re-plastering is not required to fix any of these issues. It may still be required to resolve any cosmetic damage that has been caused.

However, if the internal damage is limited, you may get away with allowing the area to dry and simply redecorating. Additionally, you may be able to use an internal damp proof paint to block any small amounts of moisture following external repairs.

Re plastering for condensation treatment

Damp caused by condensation will very rarely require replastering.

You will only need to replace plaster in cases where the damp issue has been left for an extended period. This could mean that the damp has caused irreversible damage to the plaster. However, this is quite uncommon.

Condensation is usually easy to spot. as black mould will form in areas where moisture forms. Initial treatment can be as simple as wiping black mould away or spraying with mould removal spray. Following this, a lick of paint will often be enough to completely repair any cosmetic issues.

To treat condensation your main goal should be to extract moisture from the air. This can be achieved by improving air flow and extracting moist air from rooms that suffer with high moisture content.

When replastering is a good way to stop condensation

There is one situation where replastering is actually a good way to stop condensation. This is when you have a particularly cold wall that acts as a dew point.

In this scenario the wall will be much colder than other surfaces in the room. As a result, warm moist air will condense on the wall and cause damp. In some cases, better airflow and extraction will be enough to fix this type of issue. However, there will be instances when it is not enough.

We have come across two scenarios where this commonly occurs. Both happen on exterior walls, where the outside elements are on the other side of the wall. This causes the wall to be much colder. Both scenarios can be seen below.

1. Wet plaster coat applied directly to the brickwork. This usually involves a scratch coat applied directly to the brickwork, then skim is applied over the scratch coat.
   
   This form of plastering allows the cold to conduct through the brickwork straight through the plaster. The result is a cold wall that creates a dew point for warm moist air.
   
   
2. The second example is when plaster board has been dot dabbed to the brickwork. In this case the board is not touching the wall. This means that it is not as cold. However, the cold still comes through the board adhesive forming damp patches where condensation settles.

The solution to both problems, is to remove the plaster back to the brick work and attach plaster boards using timber batons. This will create a cavity behind the board and stop cold been transferred from the masonry to the plaster.

This can be taken one step further by using insulation boards to warm the surface of the wall even further.

Conclusion             

As you can see there are many reasons that damp could occur in your property. Not all of them will need you to remove or add new plaster. However, there are a few instances where replastering is part of the job and cannot be avoided.

In some other cases, it may be an additional job to repair cosmetic damage. So, whilst it’s not an essential step to stop damp, you may need new plaster to restore your decorating.