Foundation requirements and technical planning

Laying the foundations correctly is the most important prerequisite for the assembly and long-term functionality of your garden shed. As the entire structure is designed to rest on a firm and level surface, the ground must be perfectly level and load-bearing. This is the only way to ensure that the sliding panels remain smooth-running in the long term and that the frame remains free of stress.

Foundation and edging: The technical foundation for your garden shed

The professional construction of the foundation is the most important prerequisite for the assembly and long-term functionality of your DESIGA® garden shed. As the entire structure is designed to sit on a firm, level surface, the quality of the base determines how smoothly the sliding elements operate, whether the frame remains free of stress, and ultimately the lifespan of the entire system. There are three tried-and-tested options available for the foundations: a continuous concrete base slab, a professionally laid paving surface, or compacted cobblestones. Particularly for new installations, fitting the paving into a perimeter edging made of concrete kerbstones has proven effective – the wall structure is later positioned and anchored on these stones.

The ‘80 rule’ and the ‘phase trap’: why millimetres matter

For a wall thickness of 6 cm, we recommend using 8 cm wide kerbstones, known as “80 mm kerbstones”. The extra 2 cm ensure a solid bearing surface and allow for trouble-free anchoring without the stone breaking during drilling – a risk that is very real with narrower stones and can jeopardise the entire stability of the structure. What is often underestimated here is: Almost all standard concrete blocks have a 45-degree chamfer (the so-called ‘bevel’) on their upper edges, approximately 0.5 cm wide. This bevel noticeably reduces the effective usable horizontal bearing surface – with an 80-series kerbstone, only around 7 cm of flat bearing surface often remains after deducting both bevels. Therefore, never plan the foundation dimensions to be flush with the external dimensions of the house; instead, make them approximately 1 cm larger all round. This ensures that the support feet and frame profiles rest fully on the block and do not sit in the area of the bevelled chamfer, which could lead to tilting and instability.

Plan the slope correctly: level beneath the shed, with drainage only behind it

If the foundation or decking is larger than the garden shed’s footprint, special attention must also be paid to water drainage. The immediate floor area beneath the shed must be absolutely level – a slope for rainwater drainage may only begin outside the outer edges of the garden shed. This prevents surface water from running under the floor profiles and ensures controlled drainage away from the building.

Flooring and anchoring (porcelain stoneware vs. paving stones vs. decking slabs vs. concrete slab)

The choice of flooring determines not only the appearance but also how stable your furnished garden shed will be. With an average total weight of approx. 1,500 kg and point loads of up to 150 kg (e.g. from garden tools or heavy furniture), the base should be chosen carefully.

1. Porcelain stoneware (the elegant outdoor tile)

Perfect for garden sheds used as high-quality living or working spaces.

• Advantages: 1. Extremely easy to maintain (ideal for oil or dirt). 2. Extremely abrasion-resistant and scratch-resistant. 3. Modern, elegant appearance.
• Disadvantage: With a point load of 250 kg, the tiles must be laid fully embedded in a mortar bed. Laying on pedestals is risky with these loads (risk of breakage).
• Cost: High (€€€€) – Material approx. €45–80/m².
  
  
  

2. Paving stones (The durable standard solution)

The classic choice when it comes to robustness and ease of installation.

• Advantages: 1. High dimensional stability (the stones interlock with one another). 2. Very good distribution of point loads into the sub-base. 3. Frost-resistant and durable.
• Disadvantage: Joint maintenance required (weeds/moss); usually has a somewhat rustic appearance.
• Cost: Low to medium (€€) – material approx. €15–35/m².
  
  

3. Terrace slabs (concrete or natural stone)

Large-format slabs create a calm, uniform surface.

• Advantages: 1. Quick installation over large areas. 2. Good pressure distribution due to the slab size. 3. Available in many designs (concrete look, slate, etc.).
• Disadvantage: On an uneven gravel bed, there is a risk of ‘rocking’ or edge breakage under a 250 kg point load.
• Cost: Medium (€€–€€€) – Material approx. €25–55/m².
  
  

4. The reinforced concrete slab (the premium foundation)

When it comes to a solid garden shed, the reinforced concrete slab is the most technically sound solution. If you don’t want to compromise on stability, this is the foundation for you.

Why this solution?
The combination of concrete and steel reinforcement makes this base extremely resilient and durable. Here is an overview of the key advantages:

• Absolutely no settlement: Even on softer ground, nothing warps – no sloping, no wobbling of your shed.
• Optimal anchoring: The solid slab provides the perfect foundation for securely setting heavy-duty anchors.
• Long-lasting protection: The structure effectively keeps moisture out from below, protecting the building fabric of your home.
  
  

Cost check: Concrete slab

Pro tip: Make sure to include a proper frost protection layer (crushed stone/gravel) beneath the slab to prevent frost from lifting the premium foundation in winter.

Dealing with slopes and changes in level on existing ground

Hardly any existing area in the garden is completely level. To ensure that your garden shed not only ‘sits flush’ but is also perfectly plumb, careful planning of the levelling is essential. To determine the amount of preparation required, you must first establish the existing gradient. If you do not have laser measuring equipment to hand, this can easily be done with a 1-metre spirit level: measure the height difference over a distance of exactly one metre and multiply this value by the total length of the shed. A gradient of 1 cm per metre results in a total height difference of 4 cm for a house length of 4 metres – a deviation that, without levelling, can lead to jammed sliding doors and stress cracks in the façade.

Adjustable feet as a standard solution: up to 6 cm of compensation

Our garden sheds are equipped as standard to handle minor unevenness. The special levelling feet can compensate for a height difference of up to 6 cm at the factory. However, we recommend allowing for a buffer of 3 to 4 cm to ensure optimum stability and easy fine-tuning. This leaves enough leeway to align the shed perfectly without pushing the levelling feet’s threaded rods to their limit.

Specific slope adjustment: If the ground level varies by more than 6 cm

If your existing site has a steeper slope and the absolute height difference exceeds 6 cm, conventional levelling feet reach their limits. In this case, we offer a specific slope adjustment for the entire garden shed. The structure is individually tailored to your sloping site – the result: despite the sloping ground, the Kubus stands visually harmonious and structurally sound within the landscape. This avoids unsightly large gaps between the ground and the bottom edge and guarantees maximum stability.

Protection against water and moisture

To ensure that the premium foundation and the house built upon it are protected from the elements in the long term, a three-stage protection concept comprising waterproofing, drainage and ventilation is employed.

Focus on the details

• The internal seal: The key defence against rainwater ingress. The system is designed to compensate for minor tolerances in the foundation (up to 4 mm). If your foundation has significant unevenness, additional on-site drainage is essential.
• Active drainage: A gutter in the foundation is particularly recommended in the critical area around the sliding door or along the weather-facing side. This ensures that even during heavy rain, no water presses against the threshold.
• Protection through clearance (ventilation): The adjustable feet make all the difference for the timber. The 30–50 mm gap from the ground interrupts the capillary effect: ground moisture cannot rise, and constant air circulation keeps the material dry.

Important note: If the unevenness of the ground exceeds the 4 mm limit, the profile seal alone is no longer sufficient. In this case, the foundation must either be reworked or drainage installed along the walls.

Technical interfaces (electrical, swimming pool & drainage)

The precise positioning of service pipes within the foundation is absolutely essential. Subsequent chiselling work in the reinforced concrete slab is time-consuming and weakens the structural integrity. Therefore, the rule is: plan first, then pour.

An overview of the dimensional specifications

Details on installation

• Conduit pipes for electrical wiring: To ensure that no cables lie in the way in the room, the conduit pipes should be positioned in the foundation so that they either exit directly within the wall route or discreetly in a corner. Maintain a safety distance of at least 8 cm from the outer edge of the house wall.
• Drainage & septic tank: The downpipe must be positioned precisely beneath the roof drain. Where the foundation and house are the same size, the ideal position is 10 cm from the outer corner of the foundation to the outer edge of the drainage pipe.
• Special case: pool equipment: If the house is used to house pool equipment, the thicker pipes and their fittings require more space. A distance of 20 cm from the outer edge of the wall ensures there is sufficient room for manoeuvre for tools and hands during installation or subsequent maintenance.

Planning tip for concrete foundations: Mark the positions of the pipes on the formwork before the concrete is poured, and secure them to prevent them from slipping. Even a deviation of just a few centimetres can result in a pipe ending up directly beneath a load-bearing joist later on.