- What is the essence of the idea
- The main elements of the system
- Preparation: earthwork
- Storm water drainage system
- Blind area pie
- Protective coating options
Usually the blind area is considered as an extension of the sidewalk, but does it have to be like that? Today we offer you a variant of a soft blind area – what are its decorative and functional advantages, what materials are used – and, of course, instructions for the device.
What is the essence of the idea
A soft blind area is an effective way to add variety to the exterior of your home. Concrete and paved paths have become boring for many, and they do not look natural on all types of foundations. In particular, when building a house on a pile-grillage foundation, you will have to hide the inner edge of the blind area with a hinged plinth, closing the ventilated space under the floor.
Blind areas with a hard surface are taken as the main principle – to serve as a continuation of the finishing of the basement and yard covering. The soft blind area, on the contrary, serves as a continuation of the flower bed or front garden adjacent to the house. In practice, this results in a very durable coating that does not require major repairs..
In terms of labor intensity and complexity of the device, all types of blind areas are identical, but the technique of alternating layers and laying a bulk coating has its own specifics. In particular, the blind area requires a careful selection of materials, the durability of which is not satisfactory. The external water drainage system is more complicated, but this is compensated by getting rid of the work with paving slabs or concrete.
The main elements of the system
In the classic scheme of the blind area, rain and melt water is discharged directly along the coating, and the most common scheme for its diversion is a network of open trays. In a soft blind area, this function is taken over by the surface drainage system.
There should be a highly compacted soil layer under the soft blind area. To stabilize the surface, a preparatory layer of coarse gravel is made: wedging against each other, small stones evenly distribute the load and exclude subsidence of the bulk coating.
The gravel layer also sets the main slope for water drainage. The final leveling is achieved with a loose layer of fine-grain non-porous material. Usually, sand is used, but it is possible to use granite and slag screenings, and, if necessary, warming – expanded clay crumbs.
As a hydro-barrier, geomembranes are used, which are used for waterproofing buildings to drain liquid and are known under the brands “Izostud” or “Fundalin” and others. Buildings on a strip foundation are surrounded by a soft blind area along the perimeter, like a usual one, but buildings on a pile-grillage base require the establishment of a hydro-barrier under the house of 30-50 cm.
For this reason, it is beneficial to install the blind area at the stage of foundation construction. You don’t have to worry about the safety of the gyro-insulating barrier, and the process of excavation is much more convenient to carry out this way..
Under the soft blind area, the soil is removed by a rectangular trench 40–45 cm deep below the lowest point of the site. The bottom of the trench should be at a constant level, therefore, the earthwork is preceded by a careful marking of the site with a level or water level.
The edges of the trench are not reinforced, but a groove 25 mm deep and 40 mm wide is torn off along the perimeter. Instead of a tooth of a concrete blind area, channels of a hidden storm system are located in it. Preparation of the bottom consists in strong compaction of the soil, so it is often covered with a preparatory layer of fine gravel.
Sprinkle moistened greasy clay over the leveled bottom and knead it thoroughly. The final layer thickness is 20 cm, while both a common plane and a shower channel tray are formed from the clay. When leveling clay, you need to set a total slope to the side of the building of about 5 (7): 100.
After that, the preparation layer is left to dry, periodically the surface is sprayed with small portions of water to avoid strong cracking. You can continue the device of a soft blind area after the legs cease to bind in the clay.
Storm water drainage system
The drainage of water from the blind area is carried out into the nearest drainage system. Dumping into the soil in the immediate vicinity is also possible, it depends on the annual level of precipitation in the region and the intensity of rainfall. The fact is that the abundance of flowing water can partially erode the soil under the blind area, cause its subsidence and too strong a slope of the hydro-barrier, due to which the bulk layer itself will begin to erode.
If there is no filter well or drainage channel nearby, the discharge can be done into the soil, moving 8-10 meters across or down from the general slope of the drainage system. For collecting water, both special drainage pipes and specially prepared steel or HDPE pipes with a diameter of 100 mm or more are suitable.
Preparation consists in perforating the walls with 16–20 mm holes and wrapping the pipe in a layer of needle-punched geotextile. Although the blind area has a fairly high intrinsic filtration capacity, insulation protection is needed at least in case of moisture migration from the silty soil.
At corners and intersections, the channels are connected by tee or cross-shaped manifolds with an upper outlet to ensure revision. If standard fittings for drainage systems are not used, drainage necks of surface storm sewers come to replace inspection chambers.
It is recommended to discharge water in a trench up to a meter deep, filled with 70% rubble and 30% fertile soil. One or more perforated pipes can be used here as a distributor. Note that although the canal system does not fit immediately after soil preparation, it should be assembled ahead of time while the clay dries..
Blind area pie
On top of the layer of clay preparation, a sloping layer of crushed stone with a thickness of up to 100–120 mm is poured. The fraction should be in the region of 15–20 mm, but if it is possible to alternate coarse filler with fine filler, this should be done from the bottom up. The final leveling of the slope is carried out with a 5-10 cm layer of sand or screening, the optimal deviation from the horizon is 3: 100. Part of the dump, which goes under the house in the plan, rises from 15–20 cm from the border of the facade with a steeper slope – 2:10.
The scheme of alternating layers for arranging a soft blind area: 1 – soil; 2 – clay “castle”; 3 – geomembrane; 4 – gravel; 5 – geotextile; 6 – sand and gravel preparation; 7 – geomembrane or polymer mesh; 8 – decorative layer of soft blind area; 9 – drainage pipe; 10 – geotextile
As it is laid, the blind area cake is carefully rammed and spilled with water. In addition, the stability of the bulk layer is improved by adding one layer of geotextile at the border of clay and crushed stone, and then crushed stone and sand.
After tamping, the surface of the sand must be stretched out as a rule and the geomembrane must be rolled out. It is important that no additional filling is carried out in the chute, unless only a few centimeters of sand and gravel mixture forming a slope for drainage channels.
A geomembrane is rolled out along the leveled surface, it also lines the bottom of the tray under the channel, the storm sewer pipes wrapped in geotextiles are laid and collectors are mounted. Then a layer of geocomposite 7–10 mm thick is rolled out on top of the geomembrane – it will allow even small accumulations not to linger in the embankment, but to drain freely into the channel. After that, a leveling layer of sand and gravel mixture with a thickness of about 30–40 mm is poured and easily rammed, geotextiles are rolled out on top. Everything that is poured above this border can be attributed to the decorative and protective covering of the blind area.
Protective coating options
Finally, the soft blind area is leveled with granite crushed stone of fraction 20-25 mm, creating a densely compacted layer of at least 60 mm. The separation of the layers of the embankment allows for a good compaction of the upper embankment, and the legs will not load so much in it. Offsetting the blind area 10-15 cm lower will allow you to pour a small layer of turf on top of it and bring the lawn close to the house.
In addition to filling with crushed stone, the soft blind area offers a large selection of coatings and their combinations. It can be both free-lying slabs and ceramic piece elements, pebbles, large pebbles or paved brick paths.
As for covering with paving slabs, this is not a soft blind area in its pure form. Most of the water is still discharged along the surface of the protective coating, so the requirements for the device of the cake and hydro-barrier are less stringent.