In recent times we have come to think more about our gardens, seeing them as extension of our house; another room to entertain friends, eat with the family or just simply just rest and relax.
We now consider the layout and how to get the best of the whole area and patios have become more than just an area outside the back door. Perhaps a smaller patio area in a particularly sunny spot at the back of the garden, a shady retreat under the protection of a leafy tree or an outdoor kitchen with bbq, pizza oven and a bar.
It is tempting to think that paving can be placed onto the soil, after all it’s a solid enough base for us to walk on. In the short term laying on soil or grass seems like much less work, however long term laying the paving on soil will cause problems.
The paving is much more likely to move if the base has not been dug out, levelled and compacted – movement of the base will cause rocking slabs, potential breakages of slabs as they have items moved on them at uneven levels, weeds growing through the joints. Within a relatively short period of time, the area will become unusable and need relaying.
Laying Garden Paving Slabs: Step by Step Guide
The best way to lay a patio to ensure a long lasting and secure patio can be done as follows: Tips for this process are highlighted in Italic
Tools/materials for the job
Shovel, trowel, spirit level, string line, rubber mallet, tape measure, vibrating plate compactor (ear plugs/defenders for use with), wheelbarrow or mixer, MOT Type 1, non-woven geotextile, sharp sand, cement, jointing compound, brick jointer, gloves
Digging out of the patio
Dig down by at least 150mm as to allow the new paving to be installed correctly, a certain amount of excavation will be required. The depth of this excavation will depend upon the thickness of the required sub-base plus the sand and/or mortar, and the paving flag thickness. The most important factor to consider when working out the depth of the dig is the finished surface level of the paving, when being laid up to an existing structure, must be a minimum of 150mm below the DPC to prevent problems with rising damp in the structure.
Sub-base/ Hardcore base
Fill the area with 100mm of MOT Type 1, compacting the area with the vibrating plate at least twice to a minimum depth of 75 mm. Check again for any sinking areas and add an extra depth of sub-base material if needed. Level off the area so the hardcore is flat and smooth.
The granular sub-base material should be well-graded (40mm to dust) Type 1 quality material. Sub quality material may be liable to failure under loading and be susceptible to frost or moisture movement. Recycled aggregates such as crushed masonry or concrete can be considered, provided it is well-graded and compacts to give a close textured finish. Materials containing organic matter shouldn’t be used.
A minimum longitudinal fall of 1.25% (1 in 80) and cross-fall of 2.5% (1 in 40) should be incorporated in the sub-layer construction to provide adequate surface water runoff from the wearing course.
Laying the Paving – Material Selection
Paving units should be cleaned by washing the units with a sponge and clean water. This is to remove any dust, loose material, packaging or production aids. To avoid damaging the units, stack the units on timber battens with spacers between them
If required, the backs of the units should be primed using a Paving Primer prior to placement upon the bedding mortar. This also assists bonding and helps to prevent potential marks from appearing through the paving units (reflective staining). It’s also a very useful technique for ensuring elements, such as wall copings, caps and step treads, adhere and don’t become loose.
Flags should be supported on a full ‘wet’ workable mix mortar bed of 1-part cement to 4/5 parts sharp sand. The mortar bedding should be laid to give a thickness between 30mm and 40mm (which reduces to approximately 25mm after tamping down the paving with a rubber mallet); however, some adjustment may be necessary to ensure that the units are fully supported and do not rock or move. A bonding agent can be added to the mortar to assist bonding.
Keep checking levels and gradients across the units. String lines can be helpful to define levels and lines within the laying pattern to maintain the correct joint width. Spacing packers e.g. window packers are useful for use as temporary spacers.
AVOID WALKING ON FOR A MINIMUM OF 24 HOURS AFTER LAYING
There are 2 options here, a traditional sand cement mix or newer jointing compounds.
The traditional method is cheaper but much more time consuming and labour intensive (on your hands and knees with a trowel). Whereas the jointing compounds are more expensive to buy but easier to use with a brush in the method. More information about both methods is below.
For most paving units, where a minimum of 10mm joint and minimum 22mm thick paving unit, a damp mortar mix of 1-part cement to 4-parts building sand can be used. If mortar gets onto the surface of the units, clean off immediately using a damp sponge frequently rinsed in clean water.
An Alternative is Joint it SIMPLE and can be used, provided that the joint is free draining through the mortar bed onto the sub-base or Pro Joint MAX Jointing Grout. Under no circumstances should dry or semi dry sand/cement mixes be brushed into the joints. This practice leads to staining of the paving and does not constitute a true rigid joint. Butt jointing is not recommended for any of these paving products.
There are a few things to consider for your own safety
Skin – Ensure you are wearing appropriate safety protection throughout your task. Wet mortar can burn exposed skin, so make sure you’re wearing suitable gloves and long sleeves to protect your arms.
Footwear – Experienced professionals wear steel toe capped boots, if you have these, please do wear them. If you do not have steel toe capped boots or shoes, please wear the sturdiest shoes you have, not sandals or flip-flips even if the weather is lovely!
Masks – cement dust can be harmful, when mixing and working with cement it is best to use a mask to cover your nose and mouth and mix in a well-ventilated area (outside is fine).
Look after your back – gardening and working outdoors is great exercise but if it is not something you do every day please be careful. Lift heavy items carefully and in an appropriate manner.
This all seems like a lot of hard work and effort initially but laying the paving properly will save time in the future, otherwise, you will constantly be repositioning paving on an ongoing basis.