Loose jointing has been used for many years for paved surfaces, and it’s certainly a method that can be used by people wanting to lay a driveway or patio. Once the Paving Slabs Have Been Laid, loose material such as gravel and sand is swept into the cracks between the blocks. This helps to hold them in place and prevents water getting in and undermining the foundations.
Grit and Sand for Loose Jointing
The material used will vary depending on the size of the blocks and the size of the gaps between them. With smaller blocks the gap is likely to be under a quarter of an inch (about 30mm) and sand should be used. Make sure that it is dried sand and specifically selected for jointing, not just any old sand. The grains used for jointing are selected for their interlocking properties which will increase the strength and stability of the driveway.
Larger gaps of the sort that you will be left with after laying paving slabs will need something with a bigger grain size. This can be grit or a specially prepared mix of crushed rock known as ‘splitt’. The very top of the joints can optionally be filled with a sand or dust that will combine with the exposed grit or splitt and help it stay in place.
The Loose Jointing Process
Jointing with loose material is best done in good weather when the paving stones are dry, as the small grains used for loose jointing are likely to stick together if they get damp. Simply spread the aggregate over the paved area and sweep it back and forth over the joints until it has all disappeared. Leave the filling just a little short of the surface to prevent loose material being knocked out by passing shoes or car tyres.
On commercial jobs, a vibrating compactor is often used to help the loose material settle all the way down into the joints. This speeds up the process but on a domestic job, it will be enough to top up the jointing material a couple of times as it settles. How much this will need to be done depends on how heavily the area is used – on a garden patio it may not be necessary at all, on a drive that’s used a lot you may have to do it a couple of times.
Over the first six months the joints should be inspected regularly to make sure they are bedding down. What happens is that smaller bits of dust and debris will fall into the joints and get jammed between the larger grains of sand or grit (or splitt). This helps the jointing material lock together and increases the stability of the driveway as a whole.
In the long term, occasional topping up may be necessary. If weeds get a grip in the joints, removing them will take some of the gravel away. Also the actions of the weather and vehicles will mean that gravel will continue to settle and some of it may escape into the surrounding areas.
When this happens simply top up the joints with the same material and it will look as good as new again.