With this floor construction, formwork mounted on pedestals is covered with a self-levelling anhydrite screed. This creates an installation space for electrical, climate and heating services, combined with a continuous load-bearing screed layer.
Poured Hollow Floor – the Economical Alternative for Large Areas
The poured hollow floor — also known as a wet hollow floor — offers lower material and installation costs compared with a classic raised floor. However, accessibility is limited to individual access openings built into the shell construction, rather than a fully walkable level. In large-scale areas such as office spaces, the poured hollow floor is a cost-effective alternative to the raised floor.
Structure of a Hollow Floor: Materials & Construction
The structure of a hollow floor follows a clear layer principle:
- The formwork elements are typically made from non-combustible gypsum fibre boards.
- The load-bearing layer is created using self-levelling anhydrite screed, allowing different load capacities to be achieved with ease.
- Access frames and raised floor ducts keep installations accessible.
Our guide Raised Floor or Hollow Floor explains how this structure differs from the raised floor.
What Are the Benefits of a Poured Hollow Floor?
- Ideal for large-scale applications with clearly defined use.
- More economical alternative to the classic raised floor — especially for larger areas.
- Combination of an installation void and a seamless surface — both aesthetic and functional.
What Drawbacks Should Be Considered with a Poured Hollow Floor?
- Limited accessibility – installations and cabling can only be reached via individual floor boxes; subsequent changes to the infrastructure are complex and costly.
- Long drying and curing time – the poured anhydrite screed must dry out completely before further trades can follow; this extends the construction schedule and limits flexibility on site.
- Limited flexibility for later use – unlike the raised floor, the layout of cable runs (power, IT, media) is difficult to adapt, which can become a problem with later changes of use.
Your Benefits with a Bredo Wet Hollow Floor
- Fast and precise installation by our experienced specialists
- Individually adjustable load-bearing capacities through the choice of pedestals and screed quality
- High-quality materials from our system supplier Tate Global GmbH
- Compatible with all floor coverings in our portfolio
Typical Applications
- Large-scale office and administrative buildings
- Schools and public buildings
- Commercial properties and retail
- New-build and revitalisation projects in existing buildings
With Bredo on Solid Foundations
With more than 30 years of experience in system flooring, we're happy to advise you, without obligation, on whether a wet hollow floor, a dry hollow floor or in fact a raised floor is the best choice for your project.
“The economical alternative for large-scale projects — the wet hollow floor from Bredo.”
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Poured Hollow Floors in motion
An example of what a space fitted with this system can look like – including a view of the build-up underneath. In under 20 seconds.
Ongoing process
Our process – step by step
Our clearly structured process delivers planning certainty, efficiency and the highest quality – from the initial consultation through to the finished floor solution.
01
Consultation & analysis
We begin with a personal consultation, establish your requirements and assess the spatial and technical parameters of your project.
02
On-site survey
Our specialists inspect the conditions on site, assess any existing floor systems and clarify technical details such as ceiling height, load requirements and installation needs.
03
Planning & quotation
Based on this analysis, we produce a detailed plan including technical specifications, material proposals and a transparent cost quotation.
04
Installation & quality assurance
Our installation teams deliver the project on schedule, cleanly and precisely. On completion, we carry out a quality check, provide documentation and – on request – a briefing on optimal use and maintenance.
Frequently asked questions
Frequently asked questions about Poured Hollow Floors
What screed is used for a poured hollow floor?
The standard is a calcium sulphate flow screed (CAF) to DIN EN 13813, typically with a layer thickness of 35 to 55 mm. This screed is very well suited to integrated underfloor heating. The screed grade can be adjusted to the load requirements. The screed is poured over the whole area onto the factory-prepared formwork construction.
What loads and build heights are possible?
Overall build heights range from 95 to 355 mm, with the screed top layer at 35–55 mm on formwork elements. Classification follows DIN EN 13213 by point load. Standard office areas correspond to load class 2 at 3 kN point load (6 kN breaking load). More heavily used industrial and warehouse areas can take load class 5, up to 5 kN point load (10 kN breaking load). This makes the poured hollow floor suitable for offices, schools, administrative buildings and industrial areas. Sizing is carried out on a project-specific basis.
When can the hollow floor be loaded?
The calcium sulphate flow screed can be walked on after about 48 hours and can take light site traffic after around 7 days. After 14 days, the screed can already be fully loaded, though it doesn't reach its final strength until 28 days at the earliest.
How long does drying take before the floor is ready for covering?
Readiness for covering is verified by CM measurement to DIN 18560-1. In practice, the calcium sulphate flow screed reaches readiness for covering after around 4 weeks for permeable (open) coverings. A significantly longer drying period should be expected for impermeable (closed) coverings. Drying can be accelerated using drying equipment or an integrated underfloor heating system.
Which coverings can be installed?
All common floor coverings can be laid on poured hollow floors: carpet tiles, PVC, linoleum, LVT, parquet, natural stone, porcelain stoneware, rubber and ESD-capable specialist coverings. The choice is considerably freer than with a raised floor, because there are no panel joints to accommodate. The only requirement is that the screed's residual moisture falls below the relevant threshold for the chosen covering before installation.
What fire rating does the hollow floor have?
The poured (wet) hollow floor achieves fire rating F30.
How is access to the void ensured?
Unlike a raised floor, a hollow floor isn't accessible across its entire area. Outlets therefore need to be positioned precisely during the design phase. Access hatches, cable trays and floor outlet boxes are integrated at predetermined locations.
What acoustic performance does a hollow floor achieve — and how can it be improved?
Standard constructions achieve impact sound improvement values ΔLw,P of 19–22 dB to DIN EN ISO 717-2, measured on the screed. Using impact sound insulation pads, values of up to 28 dB can be achieved. A floor covering such as linoleum, carpet or an acoustic LVT further improves sound insulation.
Can underfloor heating be integrated?
Yes. With poured hollow floors, underfloor heating can be integrated into the screed. Heat-up times, pipe spacing and screed thickness are matched to the heating concept. A drying and heat-up routine before the covering is installed is mandatory and is documented. Alternatively, the area can be conditioned via displacement air within the void — we're happy to advise on the right solution.
Matching projects
References from this area
Completed examples show how we have implemented the service described here on real projects.
Testimonials
What our customers say
“We greatly value working with Bredo — professional and a pleasure to deal with. Throughout construction, we received consistently expert advice, and the work on site was delivered reliably and to a high standard. Even short-notice requests were handled promptly. Project delivery was always goal-oriented and built on a shared understanding of the project's aims.”
“We are glad to have found a reliable, competent partner who, throughout our long-standing collaboration, has consistently delivered fast, expert solutions — even for out-of-the-ordinary work.”
“Bredo built a bespoke control room floor for our test rig that met the highest standards, both in the quality of the workmanship and in delivering on schedule.”
“For more than 10 years, we have delivered a large share of our flooring systems nationwide through a framework agreement with Bredo Doppelboden GmbH. Whether smaller individual projects or major construction schemes, Bredo handles every order with the same care and reliability we have valued for well over a decade!”
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