Cleaning Paving: Before Laying, After Installation and During Maintenance
Cleaning paving is not simply a maintenance task carried out after construction. It is an essential part of the installation process, helping to ensure correct bonding, satisfactory appearance, durability and long-term performance.
BS 7533-102, the British Standard covering the installation of modular pavements, recognises the importance of cleaning during construction, following completion and throughout the service life of a paved surface.
Whether installing natural stone, porcelain, concrete paving or clay pavers, contractors should consider cleaning at every stage of construction.
This article explains the key cleaning stages, appropriate methods and the potential consequences of inadequate cleaning.
1. Cleaning Bases and Paving Units Before Installation
Before paving units are installed, both the supporting construction and the paving materials should be inspected for contamination.
Cleaning the base
Unbound aggregate bases should be free from organic material, mud and other contamination that could compromise their performance.
Where contamination has occurred, affected material should be removed and replaced with clean, appropriately graded aggregate, which should then be compacted to the required specification.
Concrete bases should also be inspected before the bedding mortar is applied.
Any laitance, loose material, dust or contamination should be removed to provide a suitable bonding surface.
Laitance is a weak, cement-rich layer that can develop on the surface of concrete. It should be removed mechanically, typically by grinding or other suitable surface preparation methods.
Contamination may be removed using appropriate cleaning methods, including controlled low-pressure washing, provided the surface is subsequently allowed to reach the moisture condition required by the bedding system.
Cleaning paving units
Paving units can become contaminated during transportation, storage, cutting, handling and installation.
Typical contaminants include quarry dust, clay residues, cutting slurry, packaging materials, oils and general site debris.
Before installation, units should be inspected and cleaned where necessary.
Common cleaning methods include:
- Dry brushing to remove loose dust and debris.
- Water washing to remove quarry dust and cutting slurry.
- Compressed air to remove fine dust from porcelain and sawn natural stone.
Care should be taken to prevent cutting slurry from drying on the surface of paving units, particularly textured porcelain and natural stone.
Importance in bound construction
In bound paving systems, such as porcelain or natural stone installed on mortar bedding, the underside of each paving unit must be clean to allow the bonding slurry to achieve effective adhesion.
Dust, clay and other contaminants can create a separating layer between the paving unit and bonding mortar.
This can result in poor adhesion, debonding, hollow-sounding paving and premature failure.
Cleaning is therefore an important part of achieving a reliable bond between the paving unit and the bedding system.
2. Cleaning During Installation
During construction, the paving surface should be kept clean to prevent contamination of the units, bedding and joints.
Activities such as cutting paving, mixing mortar and moving materials across completed areas can introduce debris and contaminants.
Good site practice includes removing cutting slurry promptly, avoiding the transfer of mortar onto finished paving, protecting completed areas from construction traffic and keeping joints free from debris.
Mortar and cementitious materials should not be allowed to dry on the paving surface, as subsequent removal can be difficult and may require specialist cleaning products.
Particular care is required with porous natural stone, where contaminants can penetrate the surface and cause staining.
Maintaining a clean working area throughout installation reduces the risk of permanent staining and unnecessary remedial cleaning.
3. Cleaning Freshly Laid Paving
Once paving units have been installed, but before the pavement is fully completed, the surface should be cleaned to remove construction residues.
These may include cement splashes, bonding mortar, cutting dust, slurry and residues from installation activities.
Cleaning should be undertaken carefully to avoid disturbing freshly installed paving units or damaging the bedding and joints.
Loose material can generally be removed by brushing, while light water washing may be appropriate where permitted by the paving and bedding manufacturers.
Removing mortar contamination
Cementitious mortar and bonding slurry should be removed from the paving surface before they harden.
A washboy cleaning system, incorporating a sponge float and roller bucket, is particularly useful for removing fresh mortar residues without spreading contamination across the paving.
Allowing mortar to cure on the paving surface can make removal considerably more difficult.
Once hardened, cement residues may require specialist chemical treatment or mechanical removal, both of which carry a risk of damaging the paving surface.
Prevention is preferable to remedial cleaning.
4. Cleaning Paving Before Jointing
Before applying grout or jointing mortar, the joints should be inspected to ensure they are clean and have sufficient depth to accommodate the specified jointing material.
The required joint depth and width will depend on the jointing system and manufacturer’s installation instructions.
Joints should be free from loose debris, bedding mortar, cutting slurry, dust and organic material.
The paving surface should also be clean to prevent contamination of the jointing material during application.
Contaminated joints can compromise adhesion and prevent the jointing material from achieving its intended performance.
Where cementitious or resin-based jointing systems are used, particular attention should be paid to the manufacturer’s requirements for joint preparation and moisture conditions.
5. Final Cleaning Before Handover
Following completion of the installation, a final clean should be undertaken before the paved surface is handed over to the client.
This ensures the pavement is free from construction residues and presents a consistent, satisfactory appearance.
Typical activities include sweeping the paved surface, removing loose debris, washing off construction dust, cleaning residual grout or mortar contamination and ensuring drainage channels are clear.
Grout haze and surface residues
Final cleaning is particularly important with porcelain paving and sawn natural stone, where residual jointing material can leave a visible film across the surface.
Cementitious grout haze can dull the appearance of paving, while resin-based jointing materials can leave a persistent residue if cleaning is not completed correctly during installation.
The cleaning method must be appropriate for the particular residue and paving material.
Cementitious grout haze and epoxy resin haze are chemically different and generally require different cleaning products.
Acid-based cement residue removers should not be assumed suitable for resin contamination, and acidic cleaners should not be used on acid-sensitive stones such as limestone or marble.
Where chemical cleaning is necessary, a small inconspicuous test area should be undertaken first, following the manufacturer’s instructions.
6. Routine Cleaning and Maintenance
Once the pavement is in service, periodic cleaning becomes part of normal maintenance.
Routine cleaning helps preserve the appearance of the paving, maintain slip resistance and support effective surface drainage.
Organic growth, including moss and algae, can develop in damp or shaded locations. If allowed to accumulate, these deposits can create slippery surface conditions.
Regular maintenance helps prevent dirt and organic matter from becoming established.
Typical activities include sweeping leaves and debris, periodic washing, removing weeds, treating moss and algae, and replenishing lost jointing material where necessary.
Drainage channels and gullies should also be inspected and cleared to prevent blockages.
Cleaning should always be undertaken using methods that do not damage the paving units, disturb jointing materials or compromise the construction.
Pressure washing
Pressure washing can be effective for removing accumulated dirt, but excessive pressure can damage paving surfaces and dislodge jointing material.
This is particularly relevant to unbound block paving, where the jointing sand contributes to the interlock and performance of the pavement.
Where jointing sand is displaced during cleaning, it should be replenished with the specified material once the paving has dried sufficiently.
The cleaning pressure, nozzle type and working distance should be appropriate for the paving material and jointing system.
7. Specialist Maintenance Cleaning
Over time, paving surfaces can develop staining or contamination that cannot be removed through ordinary washing.
Common examples include algae, moss, atmospheric pollution, oil, grease, rust and leaf tannins.
The cleaning method should be selected according to both the contaminant and the paving material.
Common paving contaminants and cleaning methods
Moss and Algae
Brushing and suitable proprietary biocidal treatments can remove and control organic growth. Products should be approved for the intended application and used in accordance with their instructions.
Atmospheric Dirt and Pollution
Appropriate detergent-based paving cleaners can help remove accumulated dirt and environmental deposits.
Oil and Grease
Specialist degreasers and poultice treatments may be used to draw contaminants from porous paving materials. Deeply absorbed oil can be particularly difficult to remove.
Rust Staining
Proprietary rust removers, including certain oxalic-acid-based products, may be suitable depending on the paving material. Compatibility must be established before use.
Leaf Tannins
Organic staining from leaves and vegetation can often be treated using appropriate specialist paving cleaners.
Selecting the correct cleaning product
Not all cleaning products are suitable for every paving material.
Natural stone, porcelain, concrete and clay paving have different chemical and physical characteristics.
Some cleaners can alter surface appearance, damage sealers, affect jointing materials or react with minerals within the paving.
Acid-sensitive natural stones, particularly limestone and marble, require special consideration.
Cleaning products should always be selected in accordance with the paving manufacturer’s recommendations, and compatibility testing should be undertaken before treating the entire surface.
Conclusion
Cleaning is an integral part of paving construction and maintenance, rather than simply a task undertaken when the finished surface becomes dirty.
Correct preparation of bases and paving units helps ensure effective bonding, while cleaning during installation prevents contamination and staining.
Thorough joint preparation and final cleaning contribute to the appearance and performance of the completed pavement.
Once in service, regular maintenance helps preserve slip resistance, drainage and the long-term condition of the paved surface.
A clean pavement begins with correct preparation, continues throughout installation and depends on appropriate maintenance for the remainder of its service life.
