- The choice of material imposed by the environment
- Two methods of laying
- Favor the seat
- 1 SOIL DISCOVERY
- 2 IMPLEMENTATION OF THE SEAT AND SAND BED
- 3 INSTALLATION OF PAVING
Succeeding a paved terrace on a bed of sand is within everyone's reach. Provided that all steps of implementation are followed.
Cost: about 40 € / m2
Time: 1 weekend
Equipment: hedge trimmer, rake, cord, meter, vibrating plate, mason ruler, spirit level, paver cutter, pickaxe, spade, shovel, wheelbarrow, brush cutter, road broom...
This townhouse, with a raised ground floor, is located in the middle of the parcel. If it is embellished with a nice green space and a very neat terrace, on the side of the entrance, on the other hand, the general maintenance leaves something to be desired. The space of 15 m2 attached to the facade was previously adorned with a small pond in the surroundings flurries... until it becomes a no man's land invaded by vegetation that obstructs the openings overlooking the semi-buried basement. The owners have therefore chosen to turn it into a terrace.
The choice of material imposed by the environment
Access to the house is via a paved driveway. So that the whole is really uniform, the choice fell on the same product, rectangular pavers in natural stone of 10 x 20 cm and 5 cm thick. In the case of an isolated terrace, another coating could have done the trick: reconstituted stone tinted in the mass, more economical, or wood, for its warm side, for example. In the latter case, however, the implementation would have been heavier (fixing the joists on studs or a concrete slab).
Two methods of laying
For the implementation of pavers, two solutions were possible: laying on slab or on sand bed. For the first, in the absence of a concrete support, it is impossible to seal (see the article "Laying a tessellation in Roman opus", System D n° 809, June 2013). The goal of this project was to build a terrace in a short time, the only alternative was the laying of cross-joint pavers on sand bed. On this ground, the absence of unevenness and the small thickness to be disbursed are all advantages for the implementation of this method which proves to be simple and effective.
Favor the seat
The technique consists of producing a drainage sub-layer composed of sand and gravel (0 / 31.5 particle size) designed to ensure good stability and uniform compaction of the sand bed. In the presence of moist soil, drainage drains in the bottom of the excavation are also to be expected. Once compacted to the vibrating plate, the roller or the mason's lady, it is only necessary to equalize correctly the layer of fine sand (0/5), 4 to 6 cm thick, which serves support for pavers.
1 SOIL DISCOVERY
After clearing the surface of the plants with a brushcutter, start by pulling the roots off the spade and the pick.
Cut the shrubs with a hedge trimmer or chainsaw and dig around the stump. Remove it with a crowbar or other lever tool.
Dig until you reach a compact soil. On this loose soil, the depth of the disbursement is 30 cm. Tie a level cord between two stakes that will serve as a benchmark to develop the slope of rainwater (2 cm / m).
It is advisable to put a geotextile between the ground and the base layer. Objective: to prevent the two layers from mixing (which would affect the stability of the structure) and to prevent the regrowth of weeds.
2 IMPLEMENTATION OF THE SEAT AND SAND BED
Divide the embankment (gravel + sand) in the excavation, about 15 cm thick until it is flush with the height drawn on pre-planted landmarks.
Compact the bedding, if possible, with a groomer (rented), the mason's lady or a roller. Check the height after tamping. Fill in if necessary.
Now put the fine sand (particle size 0/5) on the entire surface. The final height must not exceed 10 cm.
Again, to compact the sand bed, it is best to use the groomer that sends small vibrations to compact and stabilize the soil. Check the thickness of the layer and add sand if necessary.
Plant stakes at the corners of the future terrace, checking that the remaining height is equal to the thickness of a pavement (5 cm).
Connect the stakes with a line aligned 5 cm from the sand bed. Measure at the laser level taking into account the slope (from 1 to 2 cm / m).
If the compacted soil has unevenness, place aluminum rulers or wooden battens embedded in the sand bed.
The cleats serve as a guide to level the surface using an aluminum mason ruler. Remove the excess sand and fill any gaps. Check the levels.
3 INSTALLATION OF PAVING
Start at an angle then place the rows with staggered joints (leave 10 to 15 mm between each block), starting every other row with half-pavers.
Avoid walking on the sand bed. You can also place boards wide enough to spread your weight on the pavers.
Check the alignment of each row with a large aluminum ruler placed on the sand bed against the edge of the pavers.
Make the cuts with a paver cutter, very useful for dealing with singular points. Here, the pavers are cut in trapezium to marry a stair step with rounded corners.
Once the installation is complete, fill the joints with sand, using a road broom. Water until refusal to tamp the sand and make a second pass (without rubbing the joints). Let dry 24 h to 48 h.
Laying on mortar layer
In addition to laying on a sand bed, pavers can be laid on a thin mortar. For a driveway or terrace, concrete is dosed at 150 kg / m3, and for a vehicular zone, at 200 kg / m3. The depth of excavation takes into account the thickness of the pavers (variable), the leveling of the ground and the laying bed (5 to 10 cm). The pavers are sealed in fresh concrete and then leveled (spirit level and mallet). The joints are made 24 hours after installation, with bastard mortar (white cement, gray cement and NHL lime, in equal parts). Tempered liquid, it is poured into the joints, then brushed after setting.
• Pavers of 10 x 20 x 5 cm (here 15 m2)
• Fill 0 / 31,5 (2,5 m3)
• Sand 0/5 (gravel + sand 0 / 31,5, totaling 1.5 m3)
• Polymeric sand for paver joints (Facilis, Novipro, Techniseal...)