Is a properties DPC above air bricks or below.

There are many precautions taken in a property to protect it from damp. One of the most common we hear about is the DPC (damp proof course). This is a layer of damp-proof material that forms a continuous waterproof barrier in mortar joints at the base of a property.

The DPC is commonly found around 150mm above ground level in external walls. Also, in the internal skin of cavity walls, there will be a DPC found slightly below floor level.

Another common cause of damp is poor ventilation. This happens when moisture becomes trapped in a property. When this happens, it increases the risk of damp, mold, and rot.

When we think of trapped moisture in a property, we often think of condensation building up inside the home. However, moisture caused by rising damp and penetrating damp, can also be made worse if there is poor ventilation.

dpc above air bricks

Therefore, properties have air bricks installed. An air brick is roughly the same size as a standard house brick, the difference being that it contains holes. These holes allow air to circulate in the cavity and below floor voids.

Air bricks can be installed either above, or below a properties DPC. It is more common to see them lower in properties that have suspended timber floors, with a void beneath.

Timber joists with a void just above ground level, are prone to condensation, and potential issues with rising damp. This means they benefit greatly from extra ventilation and clean air circulation.

Without airbricks, the chance of damp, rot, and other issues, such as woodworm infestation become greatly increased.

Can Air Bricks Cause Damp?

The main goal of an airbrick is to reduce damp by venting the area. But there are a few instances where they could create damp problems. This is rare, but it can happen.

Regulations state that an airbrick should be installed at least 75mm above ground level. If the airbrick is below this, it has a much greater chance of allowing water to enter the cavity. This can also be increased, if the ground outside slopes towards the property, or if the area is prone to flooding.

However, at 75mm above ground level, you are more than likely below the properties DPC. Therefore, even if water enters through the ventilation holes, it shouldn’t be able to rise above internal floor level. This could be affected by the level of water entering and the potential of a blocked cavity.

Things you need to check

If you do notice internal damp near an airbrick, these are the things you need to check:

  1. Is your airbrick less than 75mm above ground level? – This could be the result off raised floor level outside, due to something like a patio, raised beds or decking.

  2. Is there damage to your DPC? – If you do think there is damage, then you would probably benefit from an injectable DPC. These are relatively inexpensive and DIY options are available. You can read more about our favourite DPC cream here.

  3. Check your cavity for blockages. – Ideally, you would expect the cavity to extend at least 250mm below the airbrick. If material and debris collect in the cavity, this could increase the chances of moisture rising past your DPC. If this happens, moisture could bridge the cavity into your property.

  4.  Check the airbrick for blockages. – It is more likely that the airbrick causes damp, due to it not doing its job properly. If the vents become blocked, air will not be able to circulate. As a result, moisture will remain trapped, and this can cause all kinds of problems, such as worsening damp, mold, and rotten timbers.

If you do have damp and none of the above seem to be the cause, then you should probably speak with a damp-proof expert. A professional will be able to inspect the issue and find the exact cause of your problem.

Ideally, you should use an online comparison site to compare damp proofing companies. This is the most cost-effective way to hire. Also, it allows you to read previous customer reviews, so you hire a reputable company.

To see our favourite comparison site for damp proofing Click here and get up to 5 local damp quotes

TIP: Most companies will come out for a free inspection.

Can you seal airbricks?

Sealing up airbricks is nearly always a bad idea. Especially if they are original and were installed when the property was build.

The airbricks are there to provide needed ventilation for your home. Without them, you are likely to suffer with greater internal condensation. It could also cause damage to structural timbers over the long term. If timbers are damp and unable to breathe, it will drastically increase the formation of mold and rot.

Generally, air bricks will be placed in several locations around your home. Based on current regulations you will usually find one on each external wall of your property. This is a to provide even ventilation throughout the cavity and under floor voids.

In properties that have solid ground floors you may find vents higher on the wall. This is very common in ex local authority properties, where the ground floor is not a suspended timber floor.

When the vents are higher, they will often have an internal vent inside your property. These can occasionally cause a draft and it may be tempting to cover them. However, it is possible to simply block the draft with an adjustable air vent cover.

Also, if the airbrick is in a high moisture area such as your kitchen or bathroom, you could install an extractor fan. By using a fan to extract moisture, you have no need for an internal vent in that room. In this case, you could leave the external air brick to ventilate the cavity, and the extractor fan would deal with any internal moisture.


Air vents are installed in most properties and offer a needed means of ventilation. There location on a property can vary, can range all the way from 75mm above ground level. All the way up to below the roof level.

They can be placed above or below a DPC. The vents’ location will usually be based on the type of property.