Rigid paving, sometimes referred to as bound construction, requires paving to be bedded on a mortar bed with mortar joints upon a rigid base providing a solid inflexible, impermeable surface. These rigid layers above the sub base transfer loads directly to the underlying layers and require to be laid in accordance with BS7533- Pavements constructed with clay, natural stone or concrete pavers.
Though the majority of clay paving in the UK is laid as flexible or unbound construction, i.e. sand bedding with sanded joints, bound clay pavements are suitable for use in a wide range of applications for not only domestic schemes such as footpaths and patios, but also commercial projects where heavy traffic loads are anticipated.
Situations where rigid construction should be considered are: –
- – Internal paving requiring a sealed floor.
- – Commercial paving where a high incidence of cleaning with high pressure washers is required.
- – Complementing features such as existing brickwork using mortar joints.
- – Presence of existing suitable concrete slab/bound base which can be utilized.
- – Provide a solution over poor ground conditions demanding a concrete slab/bound base, or where the depth of construction needs to be reduced due to finished floor levels.
Rigid paving tends to be more labour intensive, requires periods of curing and consequently results in the most expensive method of laying paving, however, it offers longer term performance and reduced maintenance.
Temperature changes induce heavy stresses in rigid paving so inclusion of movement joints extending from the solid base to the surface must be considered and placed not exceeding 6 metres apart, particularly on larger areas of rigid paving.
Base or roadbase
The roadbase material should be constructed from a bound material, being either a bituminous macadam or concrete and should be in good condition having been thoroughly cleaned prior to placement of the mortar bedding layer and pavers. An unbound or granular type of sub base (typically Type 1 stone) must not be used for rigid construction in this position as it will continue to move resulting in cracking of the paved surface. In heavily trafficked areas requiring a greater depth of construction, a granular sub base may be used beneath the bound roadbase layer, the depth of these layers designed in accordance with anticipated traffic loadings together with the CBR strength and suitability of subgrade.
Bedding and Jointing
Designation (ii) Mortar mix (typically 1:1/2;4 cement/lime/sand) is used to bed the pavers on and as the mortar joints, however, several specialist bedding and jointing mortars are now available on the market. Please ensure any residual mortar is cleaned of immediately followed by a general cleaning down of the area using clean water once the mortar has cured. With reference to specialist bedding and mortar materials please closely follow the manufacturer’s guidelines for curing times and cleaning.
Pavers can be laid in a variety of bond patterns using a string line to ensure alignment of joints and laid to falls to avoid any ponding on the surface.
Generally, clay paving requires minimal maintenance, however, the following guidelines will help provide an ‘as new’ look throughout its life…
It is important to ensure mortared joints remain completely full and maintained, pay particular notice to the soundness of the joints following the use of a high pressure water jet. Loss of mortar from the joints may affect the integrity of the paved surface.
Resistance to staining
One of the advantages of clay paving is its ability to resist discoloration from dirt/oil/fats etc., having a relatively low water absorption and high durability preventing stains penetrating and becoming ingrained into the surface. Oil/diesel etc. tend to lay on the surface of clay pavers and are dispersed naturally. Any stubborn build up can be removed by off the shelf de-greasers followed by rinsing down with clean water. Should the area require a high incidence of cleaning to remove spilt foodstuffs etc., it may be beneficial to consider a paver sealant such as RESIBLOCK ‘22’, a specialist clay sealant www.resiblock.com/product/resiblock-22 , or similar approved.
Please be aware that some general sealants may alter the colour of any surface they are applied to and as such we would strongly recommend a trial area is determined. For further advise email [email protected]
Removal of moss/algae
To maintain a pristine appearance, particularly in north facing sheltered areas receiving little or no natural sunlight which may be overhung with trees or vegetation and very little footfall, algae may appear on the paver surface. This can easily be removed by the pressure washing to remove all debris followed by an application of an algae inhibitor, such as Agrigem’s Sapphire – https://www.agrigem.co.uk/sapphire-moss-killer-5l or similar approved. Please contact the supplier for further information regarding application guidelines.
To prevent the establishment of algae please ensure paved areas are laid to falls directing surface water into a drainage channel. Areas laid flat or have insufficient cross fall may retain moisture and detritus encouraging algae to gain hold and staining from dirt. In areas with a low footfall preventing the natural dispersion of dirt from the paving surface, it may be necessary to sweep these areas more regularly or consider the application of an algal/moss inhibitor twice a year to build up a resistance within the paved surface.
It is possible, usually preceding a lengthy period of the clay paving being saturated, such as a long wet Winter followed by a warmer and drier Spring, the surface of the pavers may exhibit a white powdery substance known as efflorescence. This is simply the accumulation of soluble salt crystals on the surface of the pavers and is totally harmless. These soluble salts, often originating from within the concrete bedding or jointing material, travel through the paver in solution and crystalize upon the surface. This temporary accumulation of salts on the paver surface will naturally blow away or can be swept away using a soft bristle brush. However, should this brief appearance be unsightly then the crystals may be dabbed off using a moist sponge using plenty of clean water which lifts the crystals off the surface. Totally saturating the affected area with a hosepipe may appear to have removed the salts, but this saturation simply dissolves the soluble salts back in to solution only to be re-absorbed by the pavers and jointing material to re-appear once again as the surface dries out. Under no circumstances apply brick cleaning solutions, such as diluted acids, as this may cause a chemical reaction subsequently ‘fixing’ the salts on the surface and possibly cause a more permanent discolouration.
Should you require any further guidance please contact Technical Support at Chelmer Valley Brick Company Ltd. Tel. 01277 219 634 or email [email protected]