Screed: Floor Structure, Underfloor Heating, and Costs

It connects the solid floor slab with the later floor covering. The screed influences heat distribution, comfort, and the durability of the floor. Errors in this area can hardly be corrected later. Therefore, clean planning was particularly important to us.

In the weeks before Christmas, the craftsmen began with the first layers of the floor structure and laid the pipes for the underfloor heating. After the windows were installed and the interior plaster was finished, the screed layer could begin his work.

Floor Structure: The Layers at a Glance

The screed forms the level foundation for the subsequent laying of parquet and tiles. While thermal and acoustic insulation is provided by the layers beneath, the screed takes on the role of the heat distributor within the underfloor heating system. Depending on the floor level, this layer structure is individually adapted to the requirements for insulation and construction height.

In the basement, the floor slab and living rooms are in direct contact with the ground. This creates an increased risk of rising damp.

For this reason, a bituminous seal was first applied to the waterproof (WU) concrete floor slab. It prevents moisture from entering the insulation layer and the screed, protecting the floor in the long term.

On the ground floor, the rooms sit on a reinforced concrete ceiling. Problems with moisture are therefore not expected. For this reason, we were able to start directly with the leveling insulation on the ceiling.

An insulation of thermal conductivity group (WLG) 035 with a thickness of eight centimeters was used. It ensures that the heat from the underfloor heating arrives where it belongs: in the living space.

Underfloor Heating Circuits: Structure, Material, and Flow Rates

23 heating circuits, around 2,000 meters of heating pipes on 200 square meters of living space: The underfloor heating supplies every room individually with heat. Each area can be adjusted separately later via the heating circuit manifolds.

Our sanitary installer laid the heating pipes over the insulation on tacker plates. These plates hold the pipes securely in position with special clips so that they do not shift when the screed is poured. At the same time, they provide insulation against impact sound.

In total, the 23 heating circuits are distributed as 13 on the ground floor and ten in the basement. Smaller rooms manage with a single heating circuit, while open areas such as the kitchen, dining, and living area require several. In the technical room and the pantry, however, we opted out of underfloor heating, and the kitchen island and kitchenette areas were also left out in the kitchen.

After commissioning, the hydraulic balancing follows. During this process, the specialist company precisely calculates and sets the flow rates for each individual heating circuit. This is the only way to ensure that the furthest corner of the living room becomes just as warm as the small guest toilet.

Laying the Screed: Material, Drying Time, and Special Features

After the sanitary installer had fixed the heating circuits, the screed layer could begin his work. A cement-based screed mortar of quality class CT-C25-F5 was used. The screed layer applied the mortar throughout the entire house within one working day and leveled it.

The specialist company implemented three requirements specifically:

• Slope in the showers: The walk-in showers need a slope towards the drains so that the water can drain away when showering.
• Recess in the technical room: The shaft integrated into the floor slab for the Pumpfix (backwater pumping station) must remain accessible. The screed layer recessed this area exactly.
• Floor box in the office: To avoid cable clutter in the future study, the company integrated a floor box for power and network cables directly into the screed layer in the middle of the room.

The screed was walkable after just a few days. Nevertheless, it takes around eight weeks before cement screed of this thickness is sufficiently dry. Regular ventilation is mandatory during this time so that the moisture from the mortar can escape.

To our luck, the installation took place just a few days before Christmas. The long drying time thus fell partly into the winter break, during which nothing was happening on the construction site anyway. By March, the screed should be ready for the floor covering. To be safe, the residual moisture will be measured beforehand using a CM measurement. This must be below 1.8%.

Screed Costs: Prices per Square Meter

The costs include the entire system structure, from the sealing in the basement to the insulation and the heated screed. In our region, the quoted prices in 2026 were around €33 per square meter.