Air Bricks: What Are They and Can You Block Them? Plus FAQs

What are Air Bricks?

Air bricks are a special type of brick that contain holes, which allow air to circulate underneath suspended floors. By improving ventilation, air bricks help reduce humidity and prevent a build-up of moisture that can lead to damp and rot.

If you notice air vent bricks on the exterior of your home, you most likely have a suspended floor. Homes that use this type of brick and have raised floors are often draughty due to poor insulation. 

They are also common in homes with fireplaces and oil heaters as they increase air circulation and disperse any harmful gases.

Can You Block Air Bricks?

You should never block or seal air bricks that act as vents for suspended floors. Without proper airflow, suspended timber floors can cause damp and will start to rot over time, potentially damaging the structural integrity of your home.

However, airbricks that have not been installed at ground level and are to help ventilate rooms, rather than floors, can be blocked if there are no gas appliances in the room. 

If you dry clothes on radiators or an electric air dryer, then this may not be suitable as poor air flow combined with high levels of condensation will lead to mould. You could use a dehumidifier to overcome this problem if you are set on blocking your room air bricks.

How to Stop Wasps, Mice, and Slugs Going in Air Bricks

A mesh cover is a great way to stop insects and rodents from getting into your house via holes in air bricks. The covers, which come in three sizes, can be attached to the wall using screws or glued using a strong adhesive. Because they contain smaller holes, they stop unwanted guests while maintaining good airflow.

How to Clean Air Bricks

The best way to clean air bricks and prevent blockages is using a long, narrow bottle cleaner with firm bristles. This will remove any buildups and ensure your subfloors are getting an appropriate level of ventilation.

How High Should Air Bricks Be?

An air brick with an enclosure in front, which protects it from water

The National House Building Council (NHBC) specify that air bricks should be at least 75mm from the ground to avoid flooding and damp issues. However, if the ground around the wall slopes away from the building and is free draining, then they can be lower than this, as water will not flow toward the vents.

If vents need to be placed below ground level, then you will need to create an enclosure that protects the brick from water. It must be 50-75mm deep and extend 600mm away from the wall. Anything smaller than this would break UK building regulations as it relies on the regular removal of leaves and other debris, which is often neglected.

Where to Put Air Bricks

Air bricks should be placed no more than 2m apart and within 450mm of the end of the wall. Ideally, they would be on all sides of the building for optimal cross ventilation. They can be placed above or below the damp proof course (DPC), it does not make a difference.

Types of Air Bricks

There are three main types of air brick in the UK – plastic, terracotta, and cast iron, also known as victorian. Terracotta clay and cast iron bricks were traditionally used, which is why you see them on older buildings. These have been replaced by plastic air bricks that are much more efficient and better at ventilation.

A standard plastic air brick provides 7,600mm2 of airflow compared to the older and less effective clay bricks, which provide as little as 1,300mm2.

If your home is vulnerable to flooding, you can buy a special type of air brick, which automatically closes the vent when water levels rise. This prevents water from getting underneath the suspended floor. It also closes during strong winds so the building does not get too draughty.

How Much Do Air Bricks Cost?

Air bricks vary in price depending on which type you require. On average a 215 x 65mm clay brick will cost £9.56, an iron cast version would cost around £15, and a modern plastic vent would cost as little as £1.99. These figures are based on retail prices and include VAT.

You may be able to negotiate a better deal if you are buying and installing a large quantity.

Do You Need Air Bricks to Ventilate a Cavity Wall?

Air bricks are not needed in cavity walls as they do not need to be ventilated. If built correctly, cavity walls should be sealed and therefore air-tight. The air inside the cavity acts as insulation and it would therefore be counterintuitive to install a vent.

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