Interior and finishes · Flooring Materials
Acoustic Floating Floor System (Isolated Deck)
Explains what an isolated floating deck is as an assembly, how it differs from a resilient underlay sheet laid under a covering, and why its behaviour is a question for a qualified acoustic professional.
Educational reference entry. Suitability depends on the complete assembly, substrate, exposure, installation method, manufacturer documentation, local requirements and qualified professional review.
Overview
What acoustic floating floor is
An acoustic floating floor system is defined by a deliberate discontinuity rather than by any one component. A deck of boards, or a screed cast on a suitable separating layer, is carried above the structural floor on resilient battens, cradles, bearers or a continuous resilient layer, and the same break is held at every wall, so that the surface people walk on nowhere bears directly on the structure below it.
The word acoustic here names the family of products and the reason people reach for them. It is not a result. What such a build-up does depends on the whole assembly as tested, on the structure it is placed upon, on the paths sound takes around it through walls, junctions and services, and on the rooms either side. That is the territory of a qualified acoustic professional, and no figure, class or rating appears on this page.
It is worth separating this from two neighbours. Floating floor underlay is a thin resilient sheet laid loose beneath a covering, not an alternative to this: an isolated deck is constructed above the structure, with its own depth, its own datum, its own perimeter isolation and its own dependencies wherever skirtings, pipes and ducts cross the break. A sprung sports floor system can present much the same section, but its resilient components are selected for how the surface deflects underfoot, while here they are selected to hold that break, and a sports hall is often asked for both at once.
Terminology
Common names and aliases
These names describe the same thing. The library keeps one entry per material so that an acronym, a trade name or a regional spelling never becomes a second, thinner page.
- resilient batten floor
- cradle and batten floor
- isolated floating deck
Applications
Common applications
Where this material is typically encountered. A typical application is not a statement that it suits your project.
- Separating floors between dwellings where an upgrade is being designed and specified by a qualified acoustic professional.
- Conversions of larger buildings into flats, where the existing floor structure is being built upon rather than replaced.
- Rooms constructed above spaces in continuing use, where the design team has asked for the deck to be isolated from the structure.
- Timber joisted upper floors where a deck is carried on resilient battens laid across or between the joists.
- Cradle build-ups over uneven concrete, where the cradles set the deck level and create a void for services at the same time.
Consideration
Where it is commonly considered
- Where a qualified acoustic professional has been appointed and is designing the separating floor as a whole rather than picking products.
- Where the floor-to-ceiling height allows a build-up of real depth without compromising doors, stairs or headroom elsewhere.
- Where the structure below has been assessed by someone qualified to comment on what it can carry.
- Where the perimeter can genuinely be kept free of contact, so skirtings, thresholds and services do not bridge the break.
- Where the programme allows the deck, the covering and the following trades to be sequenced without shortcuts at the edges.
- Where the design team is comparing an isolated deck against other routes and wants the differences described before committing.
Professional review
Where additional professional review is especially important
These are the situations where the answer depends on the specific building, and where a qualified professional should be involved before anything is decided.
- Where nobody qualified is advising on the assembly, since the value of this build-up lies entirely in how it is designed and detailed.
- Where headroom, stair geometry or existing thresholds cannot absorb the depth that an isolated deck adds to the floor.
- Where the structure below is of unknown construction or condition and has not been examined by a qualified professional.
- Where the room is a wet area, because waterproofing, drainage and the break at the perimeter interact in ways needing specialist review.
Properties
Key properties to discuss
Qualitative topics worth raising. Measured values, classes and grades come from the manufacturer's technical documentation for the specific product, not from a reference page.
- Acoustic behaviour
- Nothing about sound is claimed here. Acoustic behaviour is a property of the complete tested assembly, the structure it sits on and the rooms concerned, and it is the qualified acoustic professional, not a reference page or a product name, who establishes it.
- Substrate dependency
- The structure below governs what can be built above it. Its construction, condition, flatness and what it is judged able to carry are all matters for qualified assessment before an isolated deck is designed above it.
- Installation dependency
- The perimeter break is the whole point of the assembly, so isolation strips, the way skirtings are held clear, and the treatment of thresholds, pipes and ducts crossing the edge are what workmanship stands or falls on.
- Moisture behaviour
- A void beneath a deck and any residual moisture in the structure below both need thinking about together. Testing, ventilation of any void and the vapour strategy belong with the designer responsible for the floor.
- Maintenance
- Services routed within the void are reached by lifting the deck, so their positions should be recorded before the covering goes down. Anything fixed through the deck later risks bridging the break that was built in.
- Appearance
- The assembly is concealed, but its depth appears at every threshold, door and stair. Skirting details, ventilation of any void and edge trims are the parts an occupant actually sees and lives with.
- Documentation
- Test evidence relates to specific assemblies as tested, not to a component in isolation. Ask what assembly the evidence covers, and whether the floor being built here matches it in every respect that matters.
Exposure
Exposure and environmental conditions
- Is any part of this floor in a wet area, and how do the waterproofing strategy and the perimeter break work together there?
- What is the moisture condition of the structure below, and does the void beneath the deck need ventilating?
- Will services run within the void, and has the heat and access those services need been considered?
- Does the room's use place unusual loads or vibration on the deck, and who has been asked to comment on that?
Assembly
Substrate and system dependencies
What this material sits on, is fixed to or depends on. This is usually where performance is won or lost.
- What is the existing floor structure made of, and who has assessed it as able to carry an added build-up?
- How level is the existing floor, and are the cradles or battens being used to take up that variation?
- What depth is the whole assembly, and how does that depth work with doors, stairs and existing thresholds?
- Where does the perimeter break run, and how is it kept free of contact once skirtings are fitted?
- How are pipes, ducts and cables crossing the break detailed so they do not bridge it?
- Is a screed being cast on the deck, and if so what separating layer sits between them?
- How do junctions with walls, columns and any upstand get resolved rather than left to site judgement?
Appearance
Appearance and finish considerations
- The deck is hidden, so what shows is the level change: thresholds, door bottoms, stair risers and the line of the skirting.
- Skirtings often have to be held clear of the finished floor and sealed in a particular way, which reads as a visible detail.
- Any ventilation to the void, where it is required, needs a location that suits both the design and the room.
- Transition profiles between an isolated deck and an adjoining floor become permanent features of every doorway they cross.
Durability
Durability questions
Questions to raise rather than a service life to expect. No material has a universal lifespan — it depends on the assembly, the exposure and the upkeep.
- What does the system supplier say about loads, point loads and heavy fixed items placed on the deck?
- How do the resilient components behave over time in service, and what does the supplier state about that in writing?
- What happens if an occupant later fixes something through the deck into the structure below?
- Is the deck likely to be lifted during the building's life, and does the detailing allow for it?
- What conditions attach to any guarantee, and who is responsible for keeping to them after handover?
Upkeep
Maintenance and repair considerations
- Who records the layout of services in the void, and is that record handed over at completion?
- How would a section of deck be lifted and reinstated without damaging the isolation at the edges?
- What does the supplier say about replacing a resilient component in an area that has been disturbed?
- Who inspects the perimeter detail before skirtings are fixed, and is that inspection recorded?
Installation
Installation dependencies
What the installation depends on — not how to do it. Method belongs to the manufacturer's instructions and the trades carrying out the work.
- Which trade builds the deck, and where does it sit in the sequence relative to walls, linings and skirtings?
- How is the isolation at the perimeter installed and protected while other trades work in the room?
- What set-out drawing governs the position of battens, cradles or bearers across the floor?
- How is the deck protected from following trades before the covering is laid?
- Who is responsible for confirming that nothing has been fixed through the deck into the structure?
- What tolerance does the chosen covering demand of the finished deck, and who is achieving it?
Documentation
Documentation to request
Ask for these in writing, for the specific product being proposed, and keep them with the project record.
- The acoustic professional's design information for the floor as an assembly, not a leaflet about a component.
- The system supplier's installation instructions and detail drawings for the exact components being used.
- Details showing the perimeter break, and how skirtings, thresholds and service penetrations are treated.
- A statement of what test evidence relates to, and which assembly it was obtained from.
- The guarantee terms, including anything they require of the trades that follow the deck.
- A record drawing of any services routed within the void beneath the deck.
Conversations
Questions for qualified professionals
Bring these to the relevant qualified professional, manufacturer or authority. Requirements vary by project and location.
- Who is the qualified acoustic professional on this project, and are they designing the floor as a complete assembly?
- What total depth does this build-up add, and what does that do to headroom, doors, stairs and thresholds?
- Who has assessed the existing structure, and what did that assessment conclude about adding this build-up?
- How is the perimeter break being detailed, and who checks it before skirtings are fixed?
- What happens where pipes, ducts and cables cross the edge of the deck?
- Does the evidence you are relying on relate to the assembly actually being built here, in every layer?
- How would a section of this floor be opened and reinstated in future without spoiling the detail?
- What are the guarantee conditions, and which trades have to observe them after your work is finished?
- Why is an isolated deck being proposed here rather than a different approach, and what does it rule out?
Blind spots
Commonly overlooked points
- A single rigid fixing through the deck into the structure can undo the intent of the whole assembly.
- Skirtings, door frames and thresholds are the usual places where a carefully built break is quietly bridged.
- The depth of the build-up is decided early or it is not decided at all, because stairs and doors follow from it.
- Test evidence belongs to a specific assembly, and a floor that differs from it in one layer is a different floor.
What this page does not do
- No sound insulation figure, class or rating is stated on this page, and none should be inferred from the word acoustic in the product family name.
- Acoustic behaviour is a property of the complete tested assembly and the room, and its design belongs with a qualified acoustic professional.
- An isolated deck is not interchangeable with a resilient underlay sheet laid beneath a covering, and neither substitutes for the other.
- Nothing here addresses whether the existing structure can carry an added build-up; that is a matter for qualified structural assessment.
- Build Design Hub is published as an educational reference only, and no assembly described here is tested, approved, certified or recommended by its publisher.
Related entries
Related materials
Materials from the same family, an adjacent role in the assembly, or a shared application.
Inspiration
Related Ideas Library pages
Design directions where this material commonly appears.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this material comes up.
Go deeper
Related Build Design Hub guides
Planning guidance and neutral comparisons behind the decisions on this page.
Flooring Materials
Reference entries for floor coverings and floor surface systems — wood and engineered wood, laminate, vinyl and LVT, linoleum, rubber, cork, bamboo, carpet, terrazzo and resin.
Browse all flooring materials entries →