How to fix 11 common exterior masonry problems
Painting an exterior surface is an important aspect to any house or structure as it not only enhances the kerb appeal of a house but also gives valuable protection to the structure. However, if and when problems occur it can be a bit of a nightmare. But…fear not as Holman Paints have created a handy guide to the causes and solutions to 11 common problems with exterior masonry.
Before thinking of coating or re-coating your exterior surface…Always Remember: Preparation is Key
When decorating exteriors it is important to plan and thoroughly prepare the project. This will ensure that you achieve the best results as the paint will only perform as well as your surface preparation. Always ensure that you are using the correct preparation products and application tools for the job as this will make the job easier, result in a longer lasting finish and create better finish results. Understand that the main goal of painting and protecting exterior masonry is for Protection and Decoration. To achieve the best results, protection is achieved by creating a barrier against moisture, wind and UV rays that can all damage the surfaces and in a worst case scenario – the structure itself.
However, if problems do occur, take a look at our guide below to 11 common problems with masonry and how to fix them! Fixing them early prevent the problem getting worse and meaning a bigger job in the future.
| Problem | Cause | Solution |
|---|---|---|
| Mouldy Brickwork | Mouldy brickwork is often caused by penetrating damp that is getting into exterior surfaces. If not removed or treated, mould growth can reoccur despite a good quality redecoration. | If an exterior surface has issues with mould, treat with fungicidal wash. We recommend applying Valtti Mould Removal Solution. After application and sufficient drying time, proceed with applying masonry paint. |
| Efflorescence | New brickwork or stonework should be left for at least three months before any treatment is applied. During this time, a white powdery substance may seep out of the bricks, stone or cement. This is caused by the water dissolving the salts found within all of these materials. If Efflorescence appears on older brickwork, it is often a sign of excess moisture, and the source of the damp needs to be found before it is treated. | Clean excess efflorescence with a stiff bristle brush then coat with a weatherproof exterior masonry paint to prevent excess water getting into the masonry. Ensure that you use breathable masonry paint so that any remaining damp inside the masonry isn’t trapped. |
| Cracked Brick Stones | Often due to structural movement, cracked stone bricks are common in older houses. Although some cracks can be fixed, be wary that too many cracks point towards bigger problems such as subsidence. There are two main kinds of vertical cracking in masonry: those that run straight down and stepped cracks that follow the mortar joints in a zigzag pattern. Less commonly, cracks may also run horizontally. The other causes of cracked stone blocks are; thermal movement, differential movement, water and rust, doors and windows, shallow foundations, trees, and bad building work. | In any case of cracked stone blocks, both thermal and differential movement needs to be accommodated and this can be done by forming an expansion joint with a flexible mastic sealant. You must also notify your local building control department in advance of all structural works. When the crack has been stabilised, stepped cracks can be re-pointed with a suitable mortar or using clear, flexible mastic.
Vertical cracks will need to be replaced. We recommend that you repair and fill any damaged, old or unsound masonry using Prestonett Filler, the products are quick drying, easy to sand and do not flash through subsequent paint finishes. Prestonett Waterproof Masonry Filler is best for holes with a diameter of up to 15mm and Prestonett Exterior Quick Dry Exterior Filler for bigger holes or cracks of up to 40mm. |
| Damp Stone Blocks | Dampness in one form or another is not particularly unusual. There are several possible causes, often with more than one working in unison. For example, Driving wind and rain can penetrate solid walls where mortar joints are badly eroded. Blown faces of brick or stonework, and also cracked or loose render, can absorb rainwater like blotting paper. | First, deal with any rogue sources of water such as leaks from gutters or pipe work. Where mortar joints have become seriously eroded, they will require raking out and re-pointing with an appropriate mortar mix and style. Ensure to use a breathable material to fix your wall to ensure the damp doesn’t remain trapped. When fixed, apply weatherproof masonry paint for extra protection. An appropriate masonry coating we would recommend for this is the Murfill Waterproof Coating. This coating protects surfaces from weather and water damage whilst remaining water vapour permeable and breathable. |
| Cracked Peeling Walls | Paint can crack and flake which sometimes exposes the exterior substrate. If dry paint splits even through one coat this can lead to a complete failure of the paint. Early on the problem appears as hairline cracks, followed by flaking. This can be caused by low-quality paint on the surface with inadequate adhesion, flexibility, paint spread too thin upon application, poor priming and also painting in cold conditions. | If the cracking does not go down to the substrate, you may be able to correct it by removing the loose or flaking paint with a scraper or stiff bristle brush. Sand the area, prime any bare spots and repaint. However, if the problem exposes the substrate, remove all of the paint and thoroughly re-prime and repaint with quality exterior masonry paint. |
| Render Failure | High levels of damp within the walls are often the likely cause of render failure. Moisture and frost can become trapped between the wall and the render which first causes hairline fractures. If these hairline fractures are left untreated this will eventually cause the failure of the render. This failure of an exterior render can ultimately cause decay and damp to the interior of the building. | In most cases, only localised repairs will be required. The first job is usually to gently remove any hollow, loose and/or cracked render. This will expose bare patches of cracked render. This will expose bare patches of wall which will require adequate time to dry out before new render is applied. Ensure your new render is correctly protected and weatherproofed either with an appropriate masonry paint or coating. However, if the render failure is too extensive and widespread it will be best to remove the render and begin again with a new and more durable coating. |
| Rust on Brickwork | Accidental damage | If rusty spots appear on your bricks, you need to clean them promptly as rust can spread and cause your brick to start deteriorating. You can get your bricks rust free again by using common household products or special rust-removing chemicals. Start with the mildest cleaning product and work your way up to harsher chemicals. We would recommend starting with our own HSP cleaner/degreaser. |
| Graffiti | Purposeful damage | If graffiti occurs try cleaning the problem off the masonry using a power washer. However, it is best to pre-empt such a problem, by applying a product like the Pegagraf-Hydro Anti- Graffiti Coating before the issue occurs. Then, if Graffiti does appear simply apply Pegagraf-Hydro Cleaner for easy removal of any graffiti vandalism. |
| Uneven Surfaces | Uneven exterior surfaces can be caused by a number of issues. As long as the uneven surface is dry, sound, secure and without any of the problems mentioned above, it shouldn’t cause your surface any sufficient damage other than being a bit unsightly. | An unsightly uneven surface can be beautifully corrected and camouflaged with a simple application ofMurfill Quartz. The Murfill Quartz is a waterproof coating that covers small areas of damage and irregularities in the surface. However, before applying a coating of Murfill Quartz please ensure that the surface is thoroughly and appropriately prepared. Following sufficient drying time, the Murfill Quartz can be recoated with waterborne masonry paints so you can choose the colour of your masonry coating! This finished result is much more aesthetically pleasing than the scruffy and uneven surface of before. |
| Waterproofing Brickwork | Although this isn’t a common problem as such, waterproofing brickwork is an important aspect of exterior coatings to consider! So, if you have uncoated brickwork but you don’t actually want to coat it with masonry paint – there is a solution we can suggest. | To maintain the natural look and aesthetic of your exterior brickwork, we certainly don’t advise leaving it uncoated. Therefore, we recommend that you try a coating of Secco Super which is a colourless water repellent treatment for porous walls. Secco super is a water vapour permeable coating that does not change the colour of the surface and is ideal for dry and recently built masonry. |
| Filling and Correcting Minor Defects | Minor defects such as hairline cracks, indents and chips in the surface can cause and lead to a vast majority of the problems that have been discussed in this article. They can be caused in many different ways. However, it is exceptionally important that you correct these defects to stop your masonry problems from getting worse. It is also incredibly important as a part of the thorough preparation of an exterior surface before applying any further products. | Solution: As mentioned previously, when referring to cracked stone bricks the solution we highly recommend when correcting minor defects are the fillers from Prestonett. These fillers are great for corrective work as they are quick drying, easy to sand and do not flash through subsequent paint finishes. Prestonett Waterproof Masonry Filler is best for holes with a diameter of up to 15mm and Prestonett Exterior Quick Dry Exterior Filler for bigger holes or cracks of up to 40mm.
However, if you are after a more sound and secure repair to your exterior masonry it is possible to apply a layer of Murfill Fleece followed by a coating of Murfill Quartz. The Murfill Fleece works as a reinforcement to the Murfill Weatherproof System. This creates a strong, yet flexible and breathable coating which repairs your exterior masonry defects. |
Here at Holman Specialist Paints, we have been providing friendly, expert advice and technical guidance to our customers in the building, maintenance, furniture and metal working industries for over 25 years.
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