What is that white, powdery scum growing on your brickwork, stone, or concrete?
Try taking a lick.
Chances are it’s efflorescence and whilst appears like salt is attacking the surface, it’s not likely to be the end of the world. Prevention is better than cure, however, efflorescence may not always be entirely preventable.
In some rarer cases, efflorescence can be a warning sign of a serious problem. If you see severe efflorescence accompanied by structural issues like significant cracking, warping, rust stains, bowing, or leaning, you should contact a professional for advice from a relevant qualified tradesperson (i.e. landscape construction, builder, foundation specialists).
In this article, we speak to industry experts and take a proactive approach by identifying some preventative measures for consideration in design and construction.
We demonstrate measures that may serve as a guide for architects, designers, builders, and tradespeople in preventing, or at least reducing, moisture problems and efflorescence. This will protect all the amazing work you all do.
We will also discuss options for how to remove the unsightly, salty residue when it occurs and prevent it from returning.
What is Efflorescence?
Efflorescence is salt migrating to the surface of a porous material. The only way this can happen is with moisture. Moisture carries the salt to the surface and as it evaporates, the salt is deposited on the surface. (source: https://en.wikipedia.org/wiki/Efflorescence)
Water is the invader in this situation and it’s important to point out that water can come from both above and below the surface.
Tips for Preventing Efflorescence on Concrete
Luke Adams from Specialised Concrete Industries is an expert in concrete testing and finishing. Luke explains with regard to concrete, “Efflorescence has become a widespread problem but it’s really not all that difficult to understand how to minimise it”.
Luke suggests a few simple steps here:
- Concrete must be kept within its specified tolerance of designed slump. This way the concrete won’t bleed excessively
- Make sure excessive water is not added to the mix in the concrete truck before placement or to the top of the mix once laid
- When preparing the slab, insist concrete contractors put a plastic membrane down under the slab. This will act as a vapour barrier reducing loss of moisture from the slab and will reduce moisture silts from being drawn up from the ground
- Do your research with the concrete supplier and specify raw materials that contain less silt
- Keep moisture in the slab for the first few days i.e. wet hessian. This curing blanket helps retain the moisture in the slab, ensuring the concrete doesn’t dry out too quickly. It also assists any entrapment of efflorescence entrapment to transfer out
- Seal the concrete with a quality sealer
Whilst these measures are very beneficial, it is important to consider the salacious construction material used in the next stages of construction and the fact that moisture also comes in buckets from above when it rains. Also, consider that the moisture in certain construction materials has to transfer out. Materials like screed, adhesive, and mortar all have moisture in them.
Next, we will look at strategies for the subsequent stages of construction and the use of bricks, concrete blocks, tiles, and stone.
Tips for preventing efflorescence on Bricks, Concrete Blocks, Tiles and Stone
If the construction is in a high salt environment like near the coast, or around saltwater pools, it is even more important specifiers, builders, and tradespeople take precautions in both design and construction.
Below are ten points as a guide to help reduce efflorescence and moisture issues in bricks, blocks and stone:
- Allow concrete to properly cure before laying. Most professionals recommend 28 days cure time from the day of pouring the slab.
- Lay only completely dry bricks, blocks, and stone tiles. Make sure they stay dry when stored on construction sites by covering them and storing on pallets off the ground.
- Damp-proof detailing using membranes. When tiling consider a suitable membrane on top of the screed See Bayset’s WPA Range, also suitable capping, flashings, and weep holes as required.
- Use low-alkali mortar for stone or brick work so that alkali salts don’t leach into the masonry or stone. Also if the option is available, choose more dense stones and/or quality clay bricks.
- Cover unfinished walls, floors, and cavities during construction so water can’t get in. If it rains and the unfinished job gets wet, allow sufficient drying time before continuing. If it’s rained heavily, consider allowing a few days of fine weather before continuing. Use a moisture meter to be sure.
- Mix mortar ingredients (cement/lime/sand) exactly in the proportions specified to reduce the risk of cracking in joints. Consider mixes with a high lime-cement ratio.
- Ensure all joints that are properly filled with mortar or grout are well tooled/ironed, and a generally high standard of workmanship is maintained to prevent water from getting in through gaps.
- Seal masonry, tiles, and joints with a quality penetrating sealer (AKA Impregnating sealers) that provide additional waterproofing to the surface and joints.
- Ensure floor has adequate grading and drainage to prevent water from pooling for any length of time
- For tiles laid as pool coping and around pools, dip seal all six sides of floor tiles before they are laid and skim coat the base of tile.
For expert advice on waterproofing and tiling systems contact Bayset.
Proper Treatment of Stone in Pool Areas
In issue 15 of Discovering Stone Magazine stone expert, Jim Mann was published talking about the use of stone in pool areas.
“… consider sealing the paving units prior to installation. Dip-sealing or six-sided sealing of paving stones can reduce the uptake of moisture from the bedding as well as from the top face. This method has been found to be particularly useful where the stone is used in aggressive environments such as pool copings. A word of caution here: not all sealers are suitable for six-sided sealing as some may interfere with the bond between the paver and the bedding or adhesive.”
To learn more from Jim check out Stone Initiatives.
Suitable Types of Sealers
Solutions Sealers CONSOLIDATE is a very effective water repellant and specifically designed for dip sealing for protection against water and salt damage. It is perfect for pool coping and surrounds for materials like sandstone, terracotta, granite, limestone, concrete, brick, and some marble. CONSOLIDATE also densifies and strengthens the material, increasing it’s hardness.
Sealer expert James Carr from Solutions Sealers explains he’s seen plenty of issues relating to salt and moisture, especially around saltwater pools.
Issues like Sub-Florescence (pictured above) can occur even where an impregnating sealer was correctly applied to the top of the tiles. Without dip sealing, there is no protection from under the paver.
James admits if dip sealing tiles first with CONSOLIDATE was normal practice around pools “it would save a lot of headaches and extend the life of the tiles”.
James also suggests skim coating is a suitable adhesive to the base of the coping tiles to slow moisture uptake. Other than that, some good advice would be to maintain the quality of the pool water and manage the pool water level to 100-150mm below the coping pavers”.
How to Dip Seal
Pour CONSOLIDATE into a plastic tray so the liquid will completely cover the stone tiles to be sealed. Dip each tile in for 15 – 20 seconds. Remove and wipe off excess with a clean, lint-free, white, cotton cloth. Allow to dry for 48 hours before tiles are laid. Several days is best to ensure a complete cure.
If sealing pool coping, discuss first with the pool builder to ensure 6 sided sealing, skim coating, and water proofing membranes are incorporated as a standard part of the pool building process for the coping.
Also, check compatibility between the sealer and the tile adhesive. Make sure the strength and adhesion will not be compromised. For example, Solutions Sealers have performed successful tensile tests on sandstone and Mapei Grani-Rapid
Click this link for more information about CONSOLIDATE: http://selector.solutionssealers.com.au/files/pdfs/products/tech/consolidate.pdf and if in doubt contact the product manufacturer for technical support.
Along with dip sealing with CONSOLIDATE, for the best results, James recommends also applying a final coat of an impregnating sealer such as PRESTIGE Pool Sealer to the top side of the tiles. James cautions, “make sure the sealer chosen is suitable for the specific stone type and desired look or finish”.
PRESTIGE is a state-of-the-art impregnating sealer for specific use around pools and high moisture areas. This cost-effective sealer has been designed to help combat the effects of moisture AND staining on your stone or concrete pavers. PRESTIGE is specifically designed to strengthen the surface but still allowing the surface to breathe and doesn’t significantly alter the appearance or finish.
A key advantage of using impregnating sealers like PRESTIGE is that they don’t form a film on the surface. They penetrate deep into the substrate of the stone, masonry, or concrete. The chemistry creates bonding below the surface and subsequently, most impregnating sealers appear invisible and don’t alter the materials or the slip resistance.
SILCOPEL’S performance and price point make it a popular choice for a wide variety of construction applications.
Solution Sealers also produce an effective Water Based version called SILCOPEL WB.
This environmentally friendly sealer incorporates BIO-SAFE Technology and very LOW VOCs so it can be used more safely indoors and wherever handling solvents or solvent smells are not desirable.
James concludes, “for sure, impregnating sealers are pretty awesome chemistry, however, people should not consider them a magic potion on their own. Sealers are helpful when combined with appropriate design and materials, use of quality materials, a high standard of workmanship, and a good maintenance plan. All of these elements are equally as important in reducing the ability of water to invade a substance. The rest is up to mother nature”.
James encourages architects, designers, and builders to contact Solutions Sealers in the planning stage. Not only can Solutions Sealers help specify the correct products, but they can also provide insight into the typical behaviors of common construction materials in certain environments.
Solutions Sealers can also provide recommendations for good local applicators. Professionals who are reliable, insured, experienced, and understand product methodology as it relates the various construction materials.
Rick from A-Sured Sealing Services in Brisbane (0408 791 833) suggests often it’s simply a little patience that is needed. Whilst there is a good degree of knowledge and finesse in applying sealers, it’s really important to allow enough time for the water to naturally transfer out of the substance you are going to seal before you seal it. Rick carries a basic water meter and simply won’t seal a job if the reading is over 2%.
Mistakes with sealers can be costly! Understand the products, materials, and methodology before commencing and ALWAYS test a sample first. If in doubt contact your product supplier and a professional applicator. Ask yourself if it’s really worth the risk of a serious botch up.
We strongly recommend you don’t risk it. When the chemistry of sealers takes effect it crystallises like glass and bonds hard to the materials. It can be very difficult and expensive to rectify, therefore it is a very good idea to engage a professional like Rick.
If you don’t have a moisture meter, a simple visual method for ascertaining if water is present is to tape a sheet of black plastic over the surface and leave it for a few hours. If there is moisture present on the underside of the plastic, don’t seal it! Wait.
Gary from Restore Solutions suggests professional tradespeople would ideally carry professional equipment such as a basic moisture meter like the Trotec 660.
Stop, poor a beer, and wait.
It will take a lot longer than usual for moisture to transfer out once it’s sealed. Perhaps several weeks. That could take a few more beers. Enjoy!
How To Remove And Treat Efflorescence
Armed with a vacuum, scraping tools, and a hard bristle plastic brush, the best way to remove the early stages of efflorescence is to wait for a really dry, hot day. When the masonry, concrete, or stone is completely dry, brush it off with a coarse bristle brush and suck up the loose residue with the vacuum.
Avoid wet cleaning initially, as this usually dissolves the efflorescence allowing the salt to redeposit in the floor/wall and be sucked back into the material, only to reappear when it dries.
Once you’ve brushed/scraped off any loose material, you can sponge the surface with a damp (wrung out) synthetic chamois or high suction sponge. Use very little water and the material should dry off almost as soon as the sponge is taken away. Rinse the sponge frequently in freshwater.
If the efflorescence is advanced, it’s best to engage a professional as some equipment and chemical solutions may be required.
D-SCALE contains a powerful blend of phosphoric acid, solvents, and surfactants for removing cement and grout residues, efflorescence, rust stains, and soap scum.
D-SCALE is very effective, however, should only be used as directed as it’s not suitable for use on certain materials. Use products like D-SCALE only as directed and always test in an inconspicuous area first.
If in doubt, engage the services of a professional who will ideally have insurance and follow a process similar to the following methodology:
- Remove salt deposits with a dry process as mentioned above.
- Cover the job site in areas needing protection from chemicals.
- Wear appropriate personal protection equipment(PPE).
- Apply an appropriate product as per suppliers specification and allow sufficient dwell time.
- Agitate and extract clean with appropriate equipment.
- Remove loose grout/mortar from all joints and tile edging.
- Allow adequate drying time and check with moisture meter.
- Pre seal the empty joints and allow sealer to cure.
- Install new grout/mortar and allow adequate drying time.
- Seal surface and all grout lines with a suitable quality sealer.
Whilst mother nature is often to blame, there are some things people can do ongoing to maintain the building or structure. Simple things that will help reduce the likelihood of reoccurrence include:
- Install good ground drainage that aims to direct the flow of ground water away from the construction.
- Repair downpipes and any plumbing leads that may dump water near the construction.
- Maintain pool water levels approximately 100 – 150 mm below the pool coping.
- Avoid sprinkler systems or watering that dumps excessive water near the construction.
- Maintain your penetrating sealer through reapplication as recommended by the supplier and sooner if the material is exposed to more harsh conditions such as salt, moisture, strong UV, and high temperatures.
- If possible, avoid painting or coatings as these coated surface may easily crack, peal, or delaminate if the problem of moisture transfer persists, whereas a penetrating sealer will not delaminate and look unsightly.
As you can ascertain, there are a number of variables but it’s not rocket science. For any project it’s ideal to consult with professionals and product suppliers who understand their industry and these variables well as materials and construction techniques change.
Some steps we’ve touched on here just make sense as good standard practice, however, each project is unique so don’t just assume all processes or products will work on repeat for every project. Consider the variables in the environment, materials, design, and together you and your team will specify a moisture prevention plan that is fit for the purpose and within budget.
Thank you to all those who contributed to this article.
*DISCLAIMER: Solutions – Sealers for Stone & Tile and/or the contributors to this article, believes the information contained in this document is accurate as general advice only. As general advice only it has been prepared without taking into account the objectives, problems or needs of the reader. Solutions – Sealers for Stone & Tile has presented this information as a guide only and accepts no liability for any loss or damage caused by any error in, or omission from this document.