Next in our Simply Do It Yourself series, we look at laying patio paving.
All paving should be laid on a firm, level and well-drained base, ensuring the paving performs as it was designed to. This will ensure your patio will remain in top condition for years to come.
Vegetation and top soil should be removed to an approximate depth of 200mm across the area to be paved. Mark out this area with pegs or retaining boards and adjust their height to the required finished surface levels, ensuring that you allow the recommended fall away from any buildings and walls for water drainage. Also make sure that the finished paving surface level is at least 150mm below the level of any damp proof course. After excavation, rake level to ensure an even depth and compact the whole area using a garden roller or tamper.
It is always preferable to start with full flags laid adjacent to a fixed point such as the house or boundary wall and to work towards an edge which may be adjustable. Alternatively, start from a corner on the longest straight edge.
If you are laying more than one size of paving, particularly if in a random pattern, or if you are laying a circle or other feature, it is recommended that you dry lay the flags first to check the fit and make sure you are happy with the pattern. It is also advised that you take the paving from a number of open packs at once, even if you are just using one size, to ensure a consistent appearance to the finished patio.
Natural Stone Paving
The area to be paved should first of all be dug out to a depth of at least 200mm. The area should then be back filled with 150mm of MoT/crusher run, compacted to 100mm.
Once the area is prepared, the laying of each flag can commence. The actual mortar bed is prepared individually for each and every flag dependent on its thickness. The bed will consist of a semi-dry mortar mix, using 4 parts sharp sand to 1 part cement. Spot bedding should never be used for natural stone paving, as the flag will not be sufficiently supported.
When laying flags that will have mortar joints, the receiving edges of the already laid flags are buttered with mortar into which the new flag is pressed, forming a well filled joint, that can be topped up when pointing. Buttering will also aid consistency of joint width. Once in place, each flag can be consolidated by tapping them down, either with a rubber mallet or by keeping a piece of softwood between a hammer or mallet and the flag. Continually check levels and falls during the laying process across the top surface profile of a number of flags at a time.
Lay sandstone / limestone paving onto the full bed of semi-dry mortar, with the chamfered side down, therefore leaving the side with the largest surface area facing upwards.
The hand-dressed edge detail on sandstone and limestone paving exhibits a taper or undercut running towards the back face of the flag. When laid with suitable pointing gaps the edges of the adjacent paving will provide dovetail or reverse wedge-shaped gaps which will considerably assist the keying in of the pointing mortar thereby increasing the durability of the finished joints.Leave the mortar mix to go off for at least 24 hours before pointing.
Point with a wet mortar mix of 4:1 (building sand will be more workable), ensuring the gaps between the flags are completely filled. The strength of the pointing is extremely important, as if done incorrectly, the joints will be the weakest part of the paved area. It is important to take care not to stain the paving surface with any excess mortar as this will be difficult to remove.
A plasticiser can be added to the mortar mix to improve its workability and also ensure all air pockets are eliminated. Cement dyes may also be added to the mix to change the final colouration of your pointing mortar. Simply Paving can offer a jointing compound suitable for use with natural stone flags, please contact us directly for more information.
When laying manufactured paving, the preparation of the site should be carried out using the same methods as when laying natural stone. As manufactured paviors are produced in man-made moulds, variation in thickness is not generally an issue, and the undersides of the slabs are more consistent. Therefore, for light use patios, a screed bed of a sharp sand and cement mix (a ratio of 6:1 is more than adequate) can be used as oppose to creating a mortar bed.
If preferred, manufactured paving can also be laid on a mortar bed, but it is not always necessary.
Manufactured paving can also be pointed with a wet mortar mix, however great care must be taken to ensure it is not left on the surface of the flag as this will be almost impossible to remove when set. Many people choose to point manufactured paving with either a dry mix of sharp sand and cement brushed into the joints or a specifically designed jointing compound.
If pointing with a dry mix, a ratio of 6 parts sharp sand to 1 part cement is recommended. The dry mix should then be indirectly watered, i.e. lightly water the surface of the flags rather than the pointed joint itself. The water will then trickle into the joints and hydrate the cement, rather than splash the dry mix over the surface of the flag.
If you require any help, please give the Simply Paving office a call on 0800 032 6306 and we will try to assist you in all aspects of your landscaping project.