Laying Pavement Slabs – DIY Instructions and Prices for Concrete Slabs

Laying Pavement Slabs – DIY Instructions and Prices for Concrete Slabs

Walking around in the garden is nice, but the turf is quickly damaged by the constant shoe kicks. What follows are unsightly patches of earth where there was once a beautiful green meadow. The solution are paving slabs, which on the one hand protect the lawn and on the other hand prevent a visit to the garden from becoming a mudflat on wet days.

Pavement slabs come in a wide variety of sizes, shapes and colors. Some earth dug, the slabs laid, but after a few months or even weeks the lovingly laid path looks crooked and crooked. Although it sounds easy to build sidewalks, some knowledge is required. There are tricks and tweaks that make working easier and more efficient.

The correct laying of pavement slabs is explained in this DIY, so that the pavement gives pleasure for a long time in the same way as it was laid.

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The planning

Before actually laying the pavement slabs, good planning is necessary. Some important points need to be clarified in advance.

  • Is the path only intended as a simple access route, for example to a greenhouse?
  • Is the path used often, for example a path from the street to the front door?
  • Will the path become part of the driveway and can therefore also be used by a car?

If the path is only intended as a simple path that is not used often, a width of 80 cm is sufficient. A border is not absolutely necessary.

If the path is used more often, a width of no less than 120 cm should be assumed for the path. A border is advised to ensure a high level of stability of the path even after many years.

If the path is to be part of a driveway or is otherwise used by a car, the surface of the pavement slabs must necessarily be thicker, and curb stones are essential in this case to prevent the slabs from shifting due to the weight of the car. It should be noted that in this case paving slabs must be used that are thicker than 8 cm.

Material and tools

Paving slabs

In the planning phase, a final decision should be made as to which paving slabs are to be used. First and foremost, the slip resistance class is important for paving slabs. Especially when it rains or in winter, pavement slabs with a low slip resistance class can quickly become dangerous spots. The slip resistance classes are divided into R9 to R13, if they exist. For pavement slabs, it is essential to choose models with a slip resistance class. If the path has an incline of more than 10%, R10 should be selected, if the incline is over 19%, R11.

The second important point is the dimension. The standard formats are 30 x 30 cm, 40 x 40 cm and 50 x 50 cm. The thicknesses of the pavement slabs are 4.5 cm, 5 cm, 6 cm and 8 cm. In addition to the standard formats, there are also asymmetrical and rectangular formats. Which format you use is just as much a matter of taste as the color and structure of the stones.

The classic among the pavement slabs has been concrete slabs in different gray and anthracite tones for decades, and for several years also available in other colors, such as brown or terracotta. A distinction is made between the concrete slabs in shot-peened and concrete-smooth surfaces. Shot-peened surfaces are more secure because they have a coarser surface. There are many advantages to using concrete paving slabs. On the one hand, they are weather-resistant for decades, fit seamlessly and not dominantly into the existing ambience and are also cheaper than many natural stone paving slabs.
A disadvantage of concrete slabs, however, is the fact that both oils and greases can leave indelible traces on the concrete.

Gravel and sand layer

Coming back to the point of planning, the use of the pavement slabs determines the materials required. In addition to the pavement slabs themselves, a border must be used on a pavement that can also be used by a car. In our example, boundary stones are used. With normal paths, this is advisable for dimensional stability of the plates and optical reasons, so that even after years you have a path whose base plates do not shift.

Once the question of the edge delimitation has been clarified, the thickness of the subsurface of the pavement slabs is determined.

  • Pavement slabs have a 5 cm thick layer of sand underneath and another max. 20 cm thick layer of gravel. This is used in the case of a sandy soil.
  • If the soil has a lot of loam or clay, a 30 to 40 cm thick layer of gravel must be used.
  • A gravel layer of 30 to 40 cm is required for navigable sidewalks.
  • If the soil is loam or clay, a 50 cm thick layer of gravel must be used.

The ballast layer should consist of ballast, frost protection gravel or concrete recycling and have a grain size of 0/32.

The gravel layer and the sand layer are necessary to provide the pavement slabs with a level and safe subsurface. The ballast with its partly coarse and partly small grain size has the task of providing frozen water in the winter (water has 10% more volume in the frozen state) in the ground to provide enough space to expand so that the pavement slabs cannot move, lift or lower.

Thus, after calculating and counting the pavement slabs, which is best done on graph paper, the calculation of the gravel and sand has to be done. Gravel and sand are usually given in kilograms or tons, so the volume must be converted.

A simple mathematical formula is used for this: V = a * b * c

An example:

A 10 m long walkway, 1.20 m wide, with a 5 cm thick layer of sand.

10 m * 1.20 m * 0.05 m = 0.6 m³

  • One cubic meter of sand weighs around 1.6 tons (depending on the grain size).
  • One cubic meter of gravel weighs around 1.7 tons (depending on the grain size).

The following calculation results:

1.6 t / m3 * 0.6 m³ = 0.960 t

When calculating sand, you have to estimate 6% more because the sand is compacted. This results in a used amount of sand of 1.018 t. When calculating gravel, 3% more must be estimated because the sand is compacted.

Tool

After the materials, the following tools must now be provided:

  • Short spirit level
  • Spirit level, min. 2 m length
  • Big rubber mallet
  • Folding rule
  • Guide line / chalk line
  • shovel
  • Trowel
  • bucket
  • wheelbarrow
  • Stone saw
  • perhaps. Cross spacers

Lay paving slabs

Mark out the sidewalk

The first step is to stake out the sidewalk. With the help of several fiberglass sticks, wooden pegs or other thin sticks, the rough course of the path is first marked. To do this, the guideline is tied to a rod, stretched taut across the floor and attached to another rod. The same is now being done on the other side of the path. Care should be taken that both cords are parallel to each other. In the case of curves or changes of direction, additional bars must be inserted at the appropriate points until you have reached the shape of your walkway.

The width between the cords is the width of the path plus 20 cm on each side for the border. A 1.20 m sidewalk would therefore need a staked width of 1.60 m.

First part of the substructure

In the next step, the defined area is excavated. This can be done with a shovel and a wheelbarrow, but faster and easier with a mini excavator, which can be rented cheaply by the hour from a construction machinery store. The depth of the excavation depends on the nature of the subsoil and the use of the path as well as the height of the boundary stones used. In the excavation that has now been created, a first 5 – 10 cm thick layer of gravel (first gravel layer) is spread out straight and compacted with a vibrating plate.

Border

Once this step has been completed, the border is used. For this purpose, the previous guideline is removed and re-stretched on one side of the path. This time the string shows the exact course of the outer edge of the sidewalk. It should be noted that not only the direction, but also the height of the cord must be observed. In order to ensure optimal drainage of the rainwater, a gradient of 2% must be used. The gradient always points away from the house. Since all slabs have a 2% incline, this must also be included in the edge delimitation, otherwise unsightly edges will arise if the edge delimitation is higher than the other floor slabs.

The first edging stone (dimensions per stone in our example: 25 cm x 100 cm x 5 cm) is set up; 3 – 4 trowels of concrete are placed on the floor at the beginning and end of the kerbstone. The curb is now placed and aligned in the two piles that will be created. Its height should end with the edge of the lawn, so far it is desired that the path is at ground level. Once the slab has been aligned, the slab is fixed with concrete from the inside as well as from the outside in the lower third.

Starting from the first edge plate, all edge plates are placed one after the other on one side of the path. The guideline helps to stay in balance. A long spirit level helps to ensure an even slope and height even over long distances.

When one side is finished, proceed with the second side of the curbs in the same way as with the first. It is important for the second side that the correct distance to the first curb side is observed. The distance between the two inner sides of the curbs is the width of the slab plus its joints. A joint has a width of 2 – 3 mm.

If four pavement slabs each 30 cm wide are placed next to one another, the following picture results:

2 mm / 30 cm / 2 mm / 30 cm / 2 mm / 30 cm / 2 mm / 30 cm / 2 mm
(4 x 30 cm) + (5 x 2 mm) = 121 cm.

The distance between the kerbstones is therefore 121 cm. It should be noted that not all paving slabs are 100% the same size. The panels may have tolerances by the manufacturer. The level of tolerance varies from manufacturer to manufacturer. Pavement slabs with large tolerances should have large joint widths to compensate for this. Very dimensionally accurate panels can have a smaller spacing. A gap should not be less than 2 mm in order to ensure that rainwater drains off.

Second part of the substructure

The concrete takes some time to harden. If you were to immediately insert another layer of gravel into the frame that has now been created, the not yet dried concrete would crack and the panels would shift. So you should wait at least 2 – 3 days before the work is continued.

Another layer of grit follows. This must be heaped up to a maximum height. This height is the thickness of the pavement slabs plus a 5 cm layer of sand. In the case of 6 cm thick paving slabs, the gravel layer must end 11 cm from the upper edge of the curbs. Since the grit is compacted by the vibrating plate, it is now piled up to 10 cm in front of the upper edge and compacted again. Be careful with the vibrating plate on the curbs. There should always be 1 – 2 cm space between the vibrating plate and the curb. Directly approaching the curb with the vibrating plate can lead to unsightly chipping on it.

If the grit is compacted, the sand is now introduced, which is also compacted. This is now laid with a 2% gradient, just like the curbs.

Laying the panels

When the sub-bed is ready, you can start laying the panels. Always start in a corner, if possible, at an initial surface, e.g., a door. It is never aligned from the center. The first paving slab is now placed in the corner. If it sits a few millimeters above the edge and does not wobble, this is perfect. The pavement slab is now carefully carved into the sandy soil with a rubber mallet. The vertical position of the pavement slab is determined using a short spirit level. The slope of 2% must point to one side.

If the plate tilts or is too high or too low, the plate must be removed and sand removed or added. This is done until the slab lies in the sand bed without tilting and with the correct slope. Cross spacers can be used to help and for better alignment.

Once this first panel has been completed, the guide line is used again and the course of the joints between the panel row is determined. With a short and a long spirit level, the row is repeatedly checked for evenness.

When the first row is seated, the next row is started and the guide line for the next row is aligned. So, you continue with the other rows. Row by row.
Laying panels freely or “one panel here, one there” so that I don’t have to walk a lot is not advisable. An unsightly joint pattern can appear too quickly. For this reason, work row by row.

It is usually beneficial to start every second row with half way plates in order to ensure stability among each other.

Half panels are created with the help of an angle grinder or a stone saw, these are much larger and more powerful than small angle grinders and can be borrowed from many hardware stores. The plates are marked all around with a clearly visible, preferably colored line. With the angle grinder, the marking is now traced around the entire stone, depth approx. 0.5 cm. Only then is the plate completely cut through. This is necessary because pavement slabs tend to break by themselves after a certain cutting depth. If you scratch the pavement slabs, you create a predetermined breaking point.

Sand bars

Once all the slabs have been laid, the last step is sweeping in the sand. The gaps that are still open are now sealed using either sand or stone powder that matches the color of the pavement slabs.

The sand or stone dust is spread over the surface with a shovel and then properly swept in. Unnecessary material is simply swept up. Afterwards, a light jet of water is used, never with pressure, over the surface. The water penetrates through the joint filling and pulls the sand or stone dust with it into areas where there is no filling. When the surface is dry again, sweeping in the sand is repeated once more. Unnecessary material is swept away again. This is repeated until all gaps are filled and remain filled despite the action of water.

Now the earth can be shoveled back to the outer edges of the border and grass seeds can be scattered.

Prices for paving slabs

The price of concrete slabs is determined not only by the place of purchase, but also by shape and size. The following applies: the simpler the look and the smaller and narrower the slab, the cheaper the pavement slab.

Gray concrete pavement slabs with a thickness of 5 cm and a size of 30 x 30 cm are available from EUR 0.85. Larger panels of 50 x 50 cm are available on average for 1.20 EUR.
Pavement slabs with a sophisticated look, i.e. with natural and stone patterns, can reach prices of up to 50.00 EUR for a pavement slab of 40 x 40 x 15 cm.

Tips for fast readers

  • Usual sidewalk width 1.20 m, with little-used paths 0.80 m
  • Edge boundaries are advisable for paths, compulsory for passable areas
  • Sand underground under the slabs 5 cm
  • Gravel ground 20 cm, with loamy or clay soil 30 to 40 cm
  • Gravel ground 30 cm for drivable paths, 50 cm for loamy or clay soil
  • Slope of 2% away from the building
  • Edge borders are fixed in the bottom third with concrete
  • Use a guide line and a spirit level
  • Use cross spacers
  • Gravel and sand must be compacted with a plate compactor
  • Do not drive the vibrating plate against the curbs