Porcelain Paving Installation – Patios & Driveways

Choosing the Right Porcelain for the End Use

Depending on the intended use of a porcelain paved surface, a number of factors should be taken into account when selecting and installing porcelain. Firstly, select the correct porcelain paving for surface end usage, be this driveway, patio or pathway. A driveway should be laid to a 30mm thick porcelain paver. For a standard patio, this should be normally be laid with a 20mm or 16mm thick porcelain unit using bound system. 10mm porcelain may also be laid domestically but should be installed on a reinforced concrete slab. (Note; 10mm porcelain will be deemed as a Tile, and therefore outside of the British Standard for paving).

Patios

Assessing Porcelain Quality

As a first rule, all exterior porcelain should have a minimum R11 anti-slip rating. Consider R12 or R13 for extra anti-slip around swimming pools and hot tubs.

One way to determine the quality of porcelain is by the variation between tiles in the surface patterns. High quality products have at least 32 different ‘faces’ of surface patterns, while cheaper porcelain will have just 6 to 12 faces, with the pattern visually repeated. Ask your supplier about the “Dots Per Inch” or “DPI” rate: high quality porcelain has 650 DPI, providing the best quality high-resolution surface design. Full-body porcelain has the surface pattern or design running through the whole paving slab (see figure ) and not just a surface print veneer.

Cheaper porcelain may have a distinct baking line in its centre, caused during the manufacturing process by the way the tiles are stacked in the kiln (see figure). This makes these products less than ideal for bullnosing – the rounding of paving edges on steps or ledges as the line is physically visible.

Another indicator of good quality porcelain is a ‘rectified’ paving unit, in which the evenness of the sizes has a minimal tolerance, of approximately +/- 0.4mm. Non-rectified units have a tolerance of +/- 0.7mm.

Design and Installation Factors and Considerations

Consider the laying pattern to be used when designing the project, such as stack bond, half bond or 1/3 offset bond. Set out the area so as not to require small cuts of less than 1/3 at the edge of the paved areas: this is important not only for aesthetic reasons, but also for the structural integrity of the paved surface.

Should a stack bond be chosen as the laying pattern, rectified paving slabs should be selected due to their minimal dimensional tolerances. A stack bond is not suitable for driveways as it does not offer sufficient structural integrity for the pressures exerted by turning wheels of vehicles.

Paving slabs over 800mm long should be laid to a 1/3 offset bond. This mitigates the typical low corners of the slabs meeting the convex high middle of the slabs, which can lead to raised lips causing the paving to hold water or become a trip hazard if laid to a half bond. The British Standard BS7533:102 tolerance for level variation between adjacent paving units is +/- 2mm.

When laying porcelain, a minimum fall of 1-60 should be installed to each of the subgrade, the MOT type 1 base, the bedding mortar and the surface course. British Standard BS7533:102 recommends 1-50 and accepts 1-60 as a minimum.

Drainage must also be considered, especially where paving meets a lawn. If there is no drainage at the bottom of the end of the fall this can often cause a wet, boggy lawn, especially on clay soils. For large patios, drainage should be installed at every 10m of fall.

Should steps and copings be part of the design, full-body porcelain should be considered. As detailed above, full-body porcelain has a pattern through the whole thickness of the slab (see figures), whereas a baking line is often visible on non-full-body porcelain. This can stand out visually, especially when bullnosed. Downstands on the porcelain coping can give the illusion of a thicker paving slab.

Should full-body porcelain be unavailable, stainless steel trims and nosing details are alternative solutions.

Check Points

Upon delivery of your porcelain paving units, it is vital to check that all the batch codes match on the crates of paving. If the batch codes do not all match, contact suppliers and change the crates for all matching batch codes. Porcelain is fired in large kilns and there are visual variations between batches, even of the same named product. Differing batch codes are a warning sign that the paving slabs may differ noticeably in shade and pattern, creating an undesirable banding effect.

Prior to installation, ensure the finished level of the paving will be 150mm below the damp proof course of the house and preferably falling away from the building. Should there be no option of falling the paving away from the house, the best practice would be to ensure that the first row of paving falls away from the building, then a channel drain installed, and the rest of the paving fall towards the channel drain.

Excavation (assuming 20mm slabs to be laid)

The minimum excavation depth is be 150mm to accommodate 100mm compacted depth of MOT type 1, 30mm bedding mortar and 20mm for the paving slab. The thickness of the geosynthetic membrane and bonding mortar is approximately 3-4mm.

The best practice would be to conduct the boot test, to test the strength of the subgrade, California Bearing Ratio (CBR) as outlined in British Standard BS7533:102, and adjust the depths of excavation accordingly to meet British Standard BS7533:101.

The fall of the formation level should march that of the surface course.

Compact the subgrade using a heavy-duty vibrating compactor plate.

Base – Sub-base Installation

When installing your patio base, it is best practice to first lay a geosynthetic non-woven membrane to prevent MOT base fine particles from migrating into the subgrade. If more than one sheet is needed, ensure the geosynthetic membranes overlap by a minimum of 300mm.

Good practice, especially on poor subgrades, is to install geogrid/biaxial mesh. This is specifically designed for soil stabilisation and reinforcement. Again, geogrid should be overlapped by a minimum of 300mm and suitable zip ties installed to connect them together.

Next, install MOT type 1 to a minimum and consistent compacted depth of 100mm, and at the same fall as the subgrade. The MOT type 1 should be installed in layers, no more than 70mm in depth, which will compact to approximately 50mm depth. Compaction should consist of 5 passes both horizontally and perpendicular with a suitably heavy vibrating mechanical plate. A good indication that sufficient compaction has been achieved is there will be no visible lines in the surface of the MOT type 1.

It is good practice to ‘dip’ the base, which is a method of installing to parallel string lines. Usually, the initial string line would be 150mm below the damp proof course, and the second running horizontally parallel at the bottom of the patio 150mm from the subgrade. The string line is pulled taught every 1m to ensure there is an even distribution of MOT type 1 under the line, with no humps or hollows. Should there be low spots they can be filled with MOT type 1 and compacted, high spots may be raked to low spots or levelled.

Laying Course – Bedding Mortar

Set out string lines to levels and falls. The string line should not touch the edge of the pavers and should be 1-2mm away to ensure it is not displaced. String lines should have a tingle or intermediate line pin every 6m to prevent line sag.

Bedding mortar should consist of one part Ordinary Portland Cement (OPC) and four parts of the following aggregates: 2-6mm, 1-4mm or 2-8mm crushed rock. The mortar mix should have sufficient water added to hydrate the cement and form a ball that holds its shape in your hand when compressed with your fingers. A wet or semi-dry mix is more than acceptable, but not a dry mix.

The mortar beds should be prepared flat with no trowel marks, as this will provide a full contact mortar bed. Full contact mortar beds are essential to provide full surface area adhesion between the back of the slab and the mortar bed. Any voids may cause reflective staining in natural stone and occasionally concrete slabs, and may also cause weak spots. Under no circumstances should paving be laid to dot-and-dab or spots.

The thickness of a mortar bed should be a minimum of 30mm and no more 40mm. As an approximate guide, mostly depending on the moisture content of your mortar mix,

35-40mm will compress to 30mm. It is important to compress the mortar sufficiently when using your rubber maul to achieve maximum strength.

A good practice is to install geogrid/biaxial mesh to the mortar bed, especially on poor subgrades. This is in addition to that which may have been installed beneath the MOT Type 1 base.

Mortar in ambient temperatures is workable for approximately 2 hours; after that a new mix is required. It is considered bad practice to keep adding water to rehydrate the mortar as it loses strength.

There should be no organic matter such as leaves on the type 1 base prior to laying mortar.

Laying Porcelain Paving Units

Paving slabs should be selected from a minimum of 3 crates of the same batch number to avoid possible colour banding issues.

Check the underside of the paving slabs and see if there is a directional arrow. Directional arrows dictate the way the paving should flow in accordance with the surface pattern/design. The shading of the paving slab can alter if not all paving slabs are facing in the same direction.

Using a damp cloth or grout sponge remove engobe dust from the back of the slab, for maximum adhesion.

Check the porcelain paving units for chips.

The back of the porcelain paving units should be fully coated with a British Standard BS7533 certified bonding mortar/slurry primer, applied with a grout float or trowel at 2-3mm thickness, or filling the pattern on the back of the paving slab (see figure). The coverage should be a minimum of 95% of the back of the paving slab.

Spacers of minimum 5mm (maximum 10mm) should be used to ensure a consistent joint width. Check the spacers are tight in the joint and that they do not wobble or are loose. As there are dimensional tolerances of porcelain units it is good practice to use a string line to check, periodically, that joint lines are straight horizontally and perpendicular. Every two to three rows, measuring back to the base line, at both ends and the middle of the patio, making sure the paving is square or parallel is good practice. Usually, back measuring would involve measuring at either end and in the middle as a minimum to ensure that they are equidistant.

Using a ‘Wash-boy’, clean the paving of mortar or bonding mortar as you lay.

Rake the joints clear of mortar as you lay the paving, so a full-depth joint of grout may be installed. Do not wait until the end of the day as the mortar is likely to have hardened.

The paving should not be trodden on for a minimum of 24 hours. Clients should be made aware of this and paved areas cordoned off.

Jointing

Allow the mortar bed to cure sufficiently prior to grout installation. This can be up to 28 days in some instances. Read the manufacturer’s specifications or contact their helpline for guidance as needed. If you grout before the mortar bed has sufficiently cured, you may get efflorescence staining or water staining showing through in the grout.

The use of single part vacuum packed brush-in grouts is not recommended.

Check the weather forecast. If rain or freezing temperatures are imminent then delay grouting. If it is a warm day, ensure the air temperature does not exceed 20 degrees.

Check the joints are of sufficient depth to receive the grout, usually a minimum 20mm depth.

Clean the surface of the paving to ensure there is no contamination of the grout.

Using a leaf blower remove excess water from the joints and surface of the paving.

Install the chosen grout as per manufacturers’ specifications, ensuring the joints are full with no voids.

Thermal Movement and Expansion Joints in Porcelain Paving

In addition to selecting the correct jointing compound, consideration should also be given to thermal movement across larger paved areas. Porcelain has a very low water absorption rate but it does expand and contract with temperature change. On installations exceeding approximately five to six metres in any direction, a flexible, low modulus silicone based joint should be introduced at calculated intervals to act as an expansion joint.

This allows controlled movement within the paved surface and helps relieve stress that would otherwise be transferred into rigid grout lines. Without provision for movement, thermal expansion can lead to joint cracking, edge spalling and gradual deterioration of the surrounding bedding and pointing. Incorporating low modulus expansion joints ensures the patio can respond to seasonal temperature variation without compromising the integrity of the grout or the long term performance of the installation.

Aftercare

Regular maintenance is key, not only to the aesthetics but also to the longevity of the patio. A light power washing, with proprietary cleaners is recommended. Should any deterioration arise, these should be repaired immediate.

Sealants may be applied to the porcelain and grout.

Should the porcelain become chipped during its lifespan it may be repaired with a resin kit.

Driveways

Whereas the installation process is virtually the same on a driveway as a patio, there are some critical considerations and specifications to be made and implemented.

Design Factors & Considerations

Often, the falls on a driveway are governed by the levels of the garage floor and the pavement. Consideration should be given as to whether an adequate fall can be achieved as porcelain paving surface tension can hold water this may cause a slip hazard, especially in wet or freezing temperatures.

The choice of colour of paving slabs should be carefully considered. Tyre marks on lighter coloured porcelain will be very unsightly and can be difficult to remove.

30mm thick porcelain is recommended for driveways, however 20mm laid upon a British Standard BS7533 certified bedding mortar and over compacted Type 1 base, or a reinforced concrete slab, is acceptable

Sustainable Drainage System (SuDS) compliance regarding water management is required in the installation of a driveway, ensuring water does not run onto the highway. Aqua cells, which act in a similar way to a soak away, are often used to manage driveway surface water run-off. Aqua cells should be installed 5m from the property and 2m from a boundary. A minimum B-125 specification channel drain should be used on a driveway.

Consider the laying pattern to be used, such as half bond or 1/3 offset bond. Set out the area to ensure no small cuts of less than 1/3 at the edge of the paved areas. This is not only for aesthetic reasons but also for the structural integrity of the paving. If small cuts less than a 1/3 cannot be avoided, the ‘inboard’ cutting technique should be employed. Inboard cutting is an installation technique which eliminates small cut pieces at the edge of driveway that are usually structurally weak, and it replaces those small cuts with larger cut pieces. This often means making small alterations to the laying pattern, which is why the initial setting out important.

Note that paving slabs over 800mm long should be laid to a 1/3 offset bond to mitigate the low corners of the slabs meeting the convex high middle of the slabs, which can lead to raised lips and the paving holding water or become a trip hazard. The British Standard BS7533:102 tolerance for level variation between two paving units is +/- 2mm.

A stack bond is not suitable for driveways as it does not offer sufficient structural integrity for the turning of vehicle wheels.

As per patios, minimum fall of 1-60 should be installed to each of the subgrade, the MOT type 1 base, the bedding mortar and the surface course. British Standard BS7533:102 recommends 1-50 but accepts 1-60 as a minimum.

Excavation and Base Installation

Firstly, locating piped and cable services – such as gas, electric and broadband – as their depth is essential. A CAT scanner and Genny cable detectors are recommended. The white service boxes at the sides of newer properties show where cables and pipes enter the ground: digging carefully beneath them to locate the depth at where the pipe bends is a good indication of their overall depths.

Inspect manholes with regards to their depths to ensure that sufficient Type 1 base depth can be achieved. The structural condition of manhole chambers should be checked: often on old properties the mortar perishes between the bricks and when compacting around chambers this can cause damage and collapse.

Consider the weight of the homeowners’ vehicles, such as car, van or even motor home. Vehicles heavier than a standard vehicle will alter the design of driveways based on: refer to British Standard BS7533:101 for guidance.

• Be alert to the possibility of oil delivery vehicles parking for lengthy periods on porcelain driveways and car parking areas with their engines running causing compression. If likely, you may have to increase the base depths or select an alternative surface product.

The bare minimum excavation depth for a porcelain driveway is 210mm: 150mm MOT type 1, 30mm mortar bed and 30mm paving unit, assuming standard vehicle usage.

Should you encounter any “soft spots” in the subgrade these areas should be excavated deeper, and backfilled with MOT type 1 and compacted in layers. Carry out your due diligence in regards to the possibility of leaking or damaged drains or water pipes which should be repaired before any further works take place.

Install edge restraints to retain the driveway on a concrete race and haunch to a minimum of 50mm up the side of the edge restraint.

For compaction, use a double-barrelled roller in 100mm layers, or forward and reverse diesel whacker 40/60 plate in 70mm layers.

If you are unsure about the strength of the subgrade, conduct the heel test as outlined in British Standard BS7533:102, and adjust the depths of excavation accordingly to meet the design specified in British Standard BS7533:101.

The fall of the formation level should match that of the surface course.

Compact the subgrade.

Base – Sub-base Installation

Best practice would be to install a geosynthetic non-woven membrane to prevent fine particle migration into the subgrade. The geosynthetic membrane should overlap by a minimum of 300mm. Indeed, good practice, especially on poor subgrades, would be to install a geogrid/biaxial mesh. Again, geogrid should be overlapped by a minimum of 300mm and suitable zip-ties installed to connect them together.

Install MOT type 1 to a minimum, consistent compacted depth of 150mm, at the same fall as the subgrade. The MOT type 1 should be installed in layers no more than 70mm in depth which will compact to approximately 50mm depth. Compaction should consist of 5 passes both horizontally and perpendicular with a heavy-duty vibrating machine. A good indication that sufficient compaction has been achieved will be when no lines are seen in the MOT type 1 surface.

It is also good practice to “dip” the base which is a method of installing to parallel string lines. Usually, the initial string line would be 150mm below the damp proof course and the second string line placed at the bottom of the patio 150mm from the subgrade, with the line pulled taut every 1m to ensure an even distribution of Type 1 with no humps or hollows. Should there be low spots, these can be filled with Type 1 and compacted. High spots may be raked to low spots when grading.

Laying the Porcelain

Set out string lines to levels and falls. The string line should not touch the edge of the pavers and should be 1-2mm away to ensure it is not displaced. String lines should have a tingle or intermediate line pin every 6m to prevent line sag.

Bedding mortar should consist of one part Ordinary Portland Cement (OPC) and four parts of the following aggregates: 2-6mm, 1-4mm or 0-6mm crushed rock. Sharp sand is also an option: do not use builders’ sand as it lacks the strength of crushed rock, often has a clay content and acts like a sponge with moisture, which can cause freeze/thaw issues. The mortar mix should have sufficient water added to hydrate the cement and form a ball that holds its shape in your hand when compressed with your fingers. A wet or semi dry mix is more than acceptable, but not a dry mix.

The mortar beds should be prepared flat (see figure ) with no trowel marks (see figure ), as this will provide a full contact mortar bed. Full contact mortar beds are essential to provide full surface area adhesion between the back the slab and the mortar bed. Voids may cause reflective staining in natural stone and occasionally concrete slabs, and may also cause weak spots. Under no circumstances should paving be laid to dot and dab or spots.

The thickness of the mortar bed should be a minimum of 30mm and no more 40mm. As an approximate guide, mostly depending on the moisture content of your mortar mix, 35-40mm will compress to 30mm. It is important to compress sufficiently the mortar when using your rubber maul to achieve sufficient strength.

A good practice is to install geogrid/biaxial mesh to the mortar bed, especially on poor subgrades.

Mortar in ambient temperatures is workable for approximately 2 hours, after that a new mix is required. It is considered bad practice to keep adding water to rehydrate the mortar as the mortar loses strength.

There should be no organic matter such as leaves on the type 1 base prior to laying mortar.

Pointing and Grouting

Allow the mortar bed to cure sufficiently prior to grout installation: this can be up to 28 days in some instances. Read manufacturer’s specifications or contact their helpline to be sure. If you grout to before the mortar bed has sufficiently cured you may get efflorescence staining or water staining.

The use of single part vacuum packed brush-in grouts is not recommended.

Check the weather forecast. If rain or freezing temperatures are imminent then delay grouting.

Check the joints are of sufficient depth to receive the grout, usually a minimum 20mm depth.

Clean the surface of the paving to ensure there is no contamination of the grout.

Using a leaf blower remove excess water from the joints and surface of the paving.

Install the chosen grout as per manufacturers’ specifications, ensuring the joints are full with no voids.

Aftercare

Regular maintenance is key not only to the aesthetics, but also the longevity of your driveway. A light power washing, and proprietary cleaners are recommended. Should any deterioration occur, they should be repaired immediately.

Sealants may be applied to the porcelain and grout.

Should the porcelain become chipped during its lifespan it may be repaired with a resin kit.