A masonry sealer can help protect exposed brick, stone and concrete from moisture and weathering without hiding their natural appearance. These surfaces add natural texture and character to a home, but because they are left unpainted, they are directly exposed to rain, dirt, fungal growth and everyday weathering.
Over time, repeated moisture exposure can contribute to staining, white salt deposits, fungal or algae growth, damaged mortar joints and deterioration of the masonry surface. If you want to protect face brick, stone or exposed masonry without covering its natural appearance with paint, a clear masonry sealer can be a practical solution. Brick & Stone Sealer is designed specifically for this type of application.
What Does a Masonry Sealer Actually Do?
Our Brick & Stone Sealer is a clear, solvent-based thermoplastic acrylic coating designed to form a breathable, water-resistant barrier over unpainted brick, cement, concrete, stone and masonry surfaces. Its purpose is to help reduce water absorption while keeping the natural colour and texture of the surface visible.
It is important, however, to understand that a masonry sealer and a waterproofing system do different jobs.
Brick & Stone Sealer is ideal for protecting sound exposed masonry, but it is not intended to repair problems such as active rising damp, structural cracks, leaking parapets, failed waterproofing, damaged mortar joints or water entering the wall from behind.
If one of these problems is present, the source of the moisture should be repaired first.
Why Some Brick and Stone Surfaces Absorb More Water Than Others
Not all masonry surfaces behave the same way. A dense brick or smooth concrete surface may absorb relatively little moisture, while an older, weathered or more porous face brick can absorb water much more readily. This affects both how the wall weathers and how much sealer may be needed. A rough, absorbent brick wall can use more product than a smooth, dense concrete surface even if the two areas are the same size.
That is why it is useful to look at the condition of the wall before deciding how much product to buy.
What Is Efflorescence?
One of the most common signs of moisture moving through masonry is efflorescence. This is the white, chalky or crystalline residue that sometimes appears on brick, stone, plaster or mortar. It forms when moisture moves through the masonry and dissolves naturally occurring salts. As the water reaches the surface and evaporates, the salts are left behind.
Efflorescence is therefore more than just a cosmetic problem. It can be an indication that moisture is moving through the wall. If the white deposits continue to return, check for possible causes such as cracks, leaking gutters, defective flashing, roof or parapet problems, irrigation or poor drainage before sealing the wall.
Signs Your Masonry Surface Needs Attention
Before applying a sealer, walk around the area and look carefully at the condition of the surface. Warning signs include:
- White salt deposits
- Damp or dark staining
- Green or black fungal or algae growth
- Cracked or missing mortar
- Hairline or larger cracks
- Crumbling or powdery brick
- Flaking or damaged masonry
- Open joints
- Previous repairs that are failing
If any of these are present, they should be dealt with before the wall is sealed.
Start With a Clean, Dry and Sound Surface
Good preparation is one of the most important parts of the job. The masonry should be:
- Clean
- Dry
- Sound
- Free from dust
- Free from loose material
- Free from fungal and algae growth
A sealer cannot hold together crumbling mortar, unstable brick or loose masonry. Those areas need to be repaired first. You can remove loose dust and dirt using a stiff brush. If the wall is washed, allow it to dry thoroughly before applying any coating.
Treat Fungal and Algae Growth Before Sealing
If you can see green, black or other biological growth on the masonry, do not simply seal over it. Fungal Wash should be applied generously to affected areas and allowed to soak into the surface. After approximately 12 hours, scrub the area thoroughly with plenty of clean water and allow it to dry completely. If any fungal or algae residue is still visible, repeat the treatment.
Only once the surface is clean and dry should you continue with the sealing process.
Repair Cracks and Mortar Joints First
Cracks and damaged mortar joints can allow water to travel directly into the wall. Before sealing, inspect areas such as:
- Mortar joints
- Window and door surrounds
- Parapets and wall caps
- Corners and changes in building materials
- Expansion or movement joints
- Pipes and wall penetrations
Loose or missing mortar should be repaired before sealing. For small, non-structural cracks in suitable plaster or cement surfaces, Acrylic Crack Filler can be used for cracks up to 3 mm wide. If a crack keeps reopening or appears to be caused by movement in the building, it is better to have the cause investigated rather than simply filling and sealing it again.
Don’t Seal Over Active Damp
If a wall remains persistently damp, first find out where the moisture is coming from. Possible causes include:
- Rising damp
- Cracks
- Roof or parapet defects
- Failed gutters
- Leaking flashing
- Poor drainage
- Garden irrigation
- Plumbing leaks
- Retaining walls or soil against the wall
Brick & Stone Sealer is designed to provide a breathable, water-resistant barrier over sound masonry. Where the problem is rising or lateral damp, a more specialised damp treatment such as Damp Sealer may be the better solution as part of the correct repair system.
How to Apply Brick & Stone Sealer
Once the surface is clean, dry, sound and free from contamination, Brick & Stone Sealer is applied in two coats. Allow approximately 16–24 hours drying time between coats. Before application:
- Stir the product thoroughly.
- Apply using a brush or roller.
- Do not thin the product.
- Work steadily across the surface and maintain a wet edge.
Maintaining a wet edge simply means avoiding long breaks in the middle of a wall. Try to work from one natural stopping point to another, such as from one corner to the next. This helps create a more even appearance.
Remember That Clear Sealer Can Still Change the Look Slightly
Brick & Stone Sealer is clear, but that does not mean the masonry will look exactly the same after sealing. A clear coating can deepen the colour of brick or stone slightly and can give the surface more sheen. This can be particularly noticeable on:
- Dark face brick
- Natural stone
- Feature walls
- Variegated brick
- Highly absorbent masonry
If appearance is important, try the product on a small, less visible section first so that you can see how the colour and finish will look once sealed.
Choose the Right Weather for the Job
Avoid sealing masonry when the wall is wet or when rain is expected shortly after application. Cold, damp or humid weather can slow down drying and curing, so dry, settled weather is preferable. If the wall has recently been washed or has been exposed to heavy rain, give it enough time to dry properly before applying the sealer.
Safety and Ventilation
Brick & Stone Sealer is solvent based. Keep it away from flames and sparks and ensure there is good ventilation during application, particularly when working on indoor exposed-brick walls or in enclosed spaces. Use the appropriate protective equipment and follow the safety instructions provided with the product.
Masonry Sealer vs Waterproofing: What’s the Difference?
These products are not interchangeable. Brick & Stone Sealer is best suited to sound, unpainted brick, cement, concrete, stone and masonry where you want to reduce water absorption while keeping the natural surface visible. It helps:
- Reduce water absorption
- Improve protection against weather exposure
- Impede fungal growth
- Preserve the appearance of exposed masonry
A flexible waterproofing system, such as Flexi Rubber, Uniproof or Acrylproof, is used where a more substantial waterproof barrier is needed. These products form a visible coating over the surface, so they are a different solution from a clear masonry sealer. The right choice depends on what you are trying to fix. If your face brick or stone is in good condition and you simply want to help protect it from weather and moisture absorption, Brick & Stone Sealer may be suitable. If the wall has active moisture ingress, recurring cracking or needs a waterproof membrane, another system may be required.
Keep an Eye on the Surface Over Time
Like any exterior coating, a masonry sealer should be inspected periodically. Our Brick & Stone Sealer has a three-year life expectancy, although actual performance will depend on how exposed the wall is, the condition and porosity of the surface, the weather and how the product was applied. During routine maintenance, look out for:
- Increased water absorption
- Weathering
- Fungal or algae growth
- Cracking
- Failed mortar joints
- Discolouration
- Peeling or loss of adhesion
- New signs of moisture ingress
Catching small problems early can help prevent more extensive repairs later.
Protect the Surface Without Hiding Its Character
Exposed brick, stone and masonry do not need to be painted to gain additional protection. The most important part of the job is making sure the surface is suitable before sealing. A good approach is:
Inspect the masonry → repair cracks and damaged mortar → identify and correct moisture problems → treat fungal growth → clean and dry the surface → apply two coats of Universal Brick & Stone Sealer → allow 16–24 hours between coats → inspect the surface periodically.
When used on a sound, properly prepared surface, our Brick & Stone Sealer helps create a clear, breathable, water-resistant barrier while still allowing the natural colour and character of brick, stone and masonry to remain visible.
Visit your nearest Universal Paints Direct Outlet for advice on preparing, sealing and protecting exposed masonry around your home.
