How to Seal Brickwork: What You Need to Know

Reading time: 5 minutes

Should you seal brickwork?

Bricks are a robust and long-lasting option for exterior walls, outhouses, landscaping features and driveways, but it’s worth remembering that they are naturally porous and are not considered waterproof, so it may be beneficial to seal brick wall surfaces in some circumstances. Although modern brickwork on homes and buildings usually feature a cavity to drain water, exposed brickwork and block paving could be at risk of fading, damp and weathering, which can cause damage over the years.

It’s a good ideal to consider whether your brickwork will benefit from sealing and/or waterproofing, which depends on its use, the climate and whether it’s internal or external. You can read more about effective masonry planning with our Brickwork Checklist article.

What happens if you don't seal brick?

If you live in a low humidity climate and your home or building uses modern masonry with a cavity, you usually do not need to seal brickwork, even on exposed exterior walls. However, sealing brickwork may help it to stay strong, and resist weathering and moisture, for longer. Bricks can absorb water, which can weaken their structure, leading to a risk of fading, crumbling or letting in mould and mildew.

Here are some of the risks associated with unsealed brickwork:

• Damage through moisture - sealing will help to protect bricks, preventing freeze-thaw weathering which will need repairing at a later date

• Colour changes - sunlight can degrade a brick’s colour, and sealing also helps prevent efflorescence (a white powdery appearance from mineral deposits in the brick)

• Foliage growth - unsealed porous bricks can allow grass, weeds, moss and other foliage to grow, especially on block paving

• Crumbling bricks - spalling and cracking can happen when the outer brick later starts to come away, increasing the risk of further problems

• Mould risk - unsealed bricks can be a risk factor for mould and mildew

It’s highly recommended to seal a brick wall, patio or driveway which is used in landscaping, to help keep bricks strong, intact and looking their best.

It’s worth noting that many experts don’t recommend sealing external brick walls on homes as standard. Sealing means that water can’t escape from the brick’s pores, which may lead to problems with dampness. 

Do I need to seal interior brick?

If your interior brick walls are to be painted, there is no need to seal them before plastering takes place. However, if you have an indoor feature area with exposed brickwork, it’s recommended to seal the brick wall to prevent moisture, mould and dust from dampening your stylish interior.

Some interior brickwork isn’t designed using facing bricks but built using construction bricks, which can be dusty. Particularly if the brickwork is in an area such as a kitchen or bathroom, it will be prone to damp, so sealing the bricks will be essential. This also makes them easier to clean and will ensure they last longer.

Using a water sealant on internal brickwork will help protect it from light, moisture and wear and tear. Watered-down PVA Building Adhesive provides a good seal, as well as a good base if you choose to paint the wall at a later date. Of course, if you love the look of exposed bricks but don’t want the hassle, you could use brick slips to achieve the same effect.

Tools you will need

Firstly, you’ll need to choose which type of sealant is best for your project. There is a wide range of masonry sealers available, some of which offer glossy finishes and waterproofing, and some which don’t. It’s recommended to use a hydrophobic (water repellent) option when sealing exterior bricks for maximum effect.

As well as your chosen brick sealant to cover the appropriate area, you will need: 

• Broom

• Wire brush

• Sponge

• Bucket of water

• Mild detergent or brick cleaning formula

• Absorbent cloths or old towels

• Paint brush, roller applicator and/or spray system

• Brick repair mortar and applicator to repair existing damage (optional)

• Protective covers to prevent sealant dripping onto door frames and windows

How to seal brick wall

Before you seal brick wall areas, you’ll need to make sure the wall is dry, before scrubbing the brickwork in preparation for the sealing. It’s recommended to only seal bricks when they’re cool, so you may need to wait until the sun moves around before applying the sealant. You may need to repair any damage too, before you seal brickwork. Bear in mind that the process usually takes a few days, to allow drying in between stages.

Step 1: Brush the surface

Before you start sealing, you’ll need to sweep the brick wall thoroughly, removing any lingering dust, debris or plant material. Pay special attention to corners and joints, using the broom and wire brush to scrub all visible areas.

Step 2: Wash the bricks

Using a gentle detergent, fill your bucket with soapy water and use a sponge to clean the bricks, covering the entire surface. Remove any excess water with absorbent cloths or towels. Leave it to dry overnight.

Step 3: Repair and protect

At this point, you may want to repair any damaged bricks, or do any repointing, before leaving the wall to dry again. Once dry, and ready to seal, cover exposed windows, door frames and window sills to prevent the seal from dripping onto unwanted surfaces.

Step 4: Apply the seal

On a dry day, apply your sealant using a paint brush or roller. You could also use a low pressure spray applicator. Ideally, use horizontal strokes, starting at the top and working your way down. It’s best to apply several thin coats rather than one thick coat. Leave each coat to dry in between. The wall is then sealed and should repel water when tested.

Read more brickwork tips and building advice on our dedicated Bricks & Blocks Inspiration pages. Don’t forget to use our handy Brick Calculator to estimate how many blocks you’ll need for your project.

How to Seal Brickwork: FAQs

What is the best way to seal a brick wall?

Before you seal brick wall areas, you’ll need to make sure the wall is dry, before scrubbing the brickwork in preparation for the sealing. It’s recommended to only seal bricks when they’re cool, so you may need to wait until the sun moves around before applying the sealant. You may need to repair any damage too, before your seal brickwork.

Does brick sealer stop damp?

Sealing brickwork can help stop rain and water from penetrating through bricks, which can lead to mould and mildew. If the dampness increases in heavy rain, brick sealer should help avoid this. However, if the damp is caused by interior ventilation issues this may not prevent the problem from recurring.

What happens if you don't seal brick?

Some modern brickwork with a cavity to drain excess water won’t need sealing, but other brick walls can benefit from being sealed, helping them to last longer and look their best. Bricks can absorb water, which can weaken their structure, and unsealed bricks are at risk of fading, crumbling or letting in mould and mildew. Damp bricks can also encourage moss and weeds to grow, especially on block paving.

How long does brick sealing last?

Most masonry and brick sealers will last up to around 5 years, when applied correctly. This will depend on the climate, wall use and exposure. Some brands even claim to last up to 25 years before needing to be re-sealed.

Can you waterproof exterior brick?

Bricks are porous and are not waterproof, meaning they can sometimes let in water and damp, but you can make them waterproof by applying a water repellent sealant - such as siloxanes and silanes. This will not only help protect your brickwork from damage, but keep rain and moisture out of your home.

How often should exterior brick be sealed?

Not all brickwork needs to be sealed, but if you do seal brick walls - experts recommend re-sealing it around every 5 years, or when the bricks are no longer hydrophobic. Some brands claim that their masonry sealant can last up to 25 years. If in doubt, you can test if the surface is still water repellent by applying water to the brick and seeing if it's absorbed, requiring a re-seal.

Disclaimer: The information contained on this page is intended as an overall guide and is not intended as specific advice from a qualified professional on how to seal brickwork in every situation. Always read the product label first and follow the manufacturer’s instructions.