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Decking boards are considered modern because they combine a natural, comfortable material with a high-quality look. Above all, the right substructure is important for lasting joy. We explain what is important when laying decking.

In a nutshell

  • The subsoil should be stable, level and ideally designed to allow infiltration
  • An intermediate layer must be used as a load-bearing and
  • mounting level for the actual floorboards
  • Substructure must be strong enough to withstand deformation of the wooden floorboards

Special case decking boards

Ultimately, decking boards are just a covering, such as concrete slabs, plaster or similar. Or maybe not? No. Because in contrast to the named coverings made of mineral natural or artificial products, a wooden terrace has significantly different properties and requirements for which the substructure must be designed:

  • Transmission or absorption of movements in the wood (shrinkage, swelling)
  • Securing the position of warping floorboards against lifting off the ground
  • safe ventilation of moisture from the wood
  • Avoid standing water on the wood

The basic construction

Now there are a number of ways that build on one another or that complement one another in order to fulfill all of these tasks. However, the general procedure is always the same. A substructure ensures a stable and water-draining subsoil. This is followed by an intermediate construction that establishes contact with the subsoil. You can then lay the decking boards on top of that.

The minimum

The cheapest and easiest way to create a load-bearing and at the same time draining substructure is a compacted gravel bed that reaches down to frost-proof ground. The low effort and the low costs are countered by the fact that with this simple solution you have to form the following substructure together with the terrace floorboards into a disc that is as stiff as possible. Anchoring in the substructure to prevent the floorboards from lifting off is not possible.

  • Floor area of the terrace + excavate 80 centimeters on all sides, depth at least 80, preferably 100 centimetres
  • Install gravel, KFT (combined frost protection and base layer) or mineral concrete in layers
  • After layer height 30 centimeters level off and compact with vibrating plate
  • Tapered infill from the edge at a 45 degree angle
  • The final layer is therefore the same size as the planned terrace
  • fill the remaining space above the gravel embankment with soil
  • Apply fine chippings for the subsequent construction and level off with a straight edge and laser spirit level, limit the layer thickness to a minimum

Notice: Choose a vibrating plate that is not too large. One may be tempted to "simplify" the work with a device that is as powerful as possible. In fact, however, small vibratory plates are much more mobile and are completely sufficient in terms of compaction performance.

additions that make sense

Either place your substructure directly on this frost-proof and load-bearing subsoil, or you add another step to the structure, which allows you to have a cleaner structure and even better drainage of rainwater. In addition, the load is distributed more evenly in the gravel bed and localized sagging is prevented.

  • Lay terraces or paving slabs made of concrete, aggregate concrete, etc. individually on a layer of gravel
  • Location in the middle under planned beams
  • Choose longitudinal distances along the straps between 60 and 80 centimeters
  • After laying the grid, check the height with a straightedge
  • If necessary, underlay individual panels with fine gravel until the top edges of the panels are level

The permanent alternative

Now, instead of laying concrete slabs, you can build individual concrete foundations at their locations:

  • Dig the soil at least 30 x 30 centimeters, at least 80 centimeters deep
  • Fill the earth quiver with quick-setting concrete
  • Align the upper edge of all foundations evenly when filling with a plumb line or laser spirit level
  • Keep concrete wet while curing

Notice: The concrete foundations later allow you to anchor the actual substructure securely and securely in the concrete. Heavy-duty dowels are suitable for this, which are driven into a drill hole and securely hold the screws of the construction.

The liner

Now follows the actual substructure for the wooden floorboards. The same wood is often used here as for the floorboards themselves. But special aluminum profiles are also available. These further reduce the problem of moisture and generally enable even lower installation heights.

  • Cover the subsurface with dark root fleece (prevents plants from growing between the floorboards and forms a dark background of the floorboard joints)
  • Align the wood or profiles lengthwise, lateral distances usually 60 to 80 centimeters depending on the thickness of the floorboards
  • When using concrete slabs, align them centrally on the slabs
  • Check that all timbers or profiles are parallel
  • Check height with spirit level or plumb line
  • If necessary, support them individually, e.g. with wooden or metal discs
  • for foundations: anchor in the foundations using heavy-duty anchors

frequently asked Questions

Why does a flat substructure made of concrete make no sense?

With a flat concrete slab you create a sealed level from which you have to drain the rainwater with great effort. The advantage of a permeable plank construction is lost.

Why can't decking boards be laid tightly?

Wood swells, shrinks and moves with moisture, temperature and age. Boards that are laid close together can build up so much pressure when they swell that the attachment to the substructure is destroyed.

What can go wrong with a minimal design?

The weaker the substructure is, the easier it is to give in to the pressure of warping wooden floorboards. Back anchoring in the ground, as is possible with concrete foundations, makes sense, especially with minimized aluminum profiles for particularly low installation heights. Otherwise, the planks can selectively lift the entire covering from its support if the boards curve upwards under the sun and rain.

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Category:

Garden design