Levelling large floor height differences with a dry floor

Two adjoining rooms with subfloors at different heights, or one large room with a steeply sloping subfloor: you want one level floor throughout. A suitable dry floor build-up can accommodate these differences. Where needed, combine the green Staenis dry floor grid with CircoFloor, including within the same room.

Can the OSB run continuously across the floor? Yes: first lay 12 mm OSB on the dry floor grid. Set the grid 12 mm lower than CircoFloor to allow for this. An 18 mm OSB layer can then run across both zones. The fictitious example below explains the principle.

First establish the finished floor level

Use the same horizontal laser reference throughout. Mark the desired finished floor level and measure down to the existing subfloor at several points. On a sloping floor, measure from the highest to the lowest zone, including points in between. This establishes the available height across the floor.

Keep four levels separate: the existing subfloor, the top of the supporting structure, the top of the OSB boarding and the top of the final floor covering. Label each measurement accordingly. Allow for the underlay, floor covering and any additional layers before adjusting the systems.

Different floor coverings may have different thicknesses. In that case, a level OSB surface does not automatically produce the same finished floor level. Read how to measure floor heights correctly with a laser.

Use one system or combine two?

One system may be enough if its adjustment range and the complete build-up fit throughout. Combining systems becomes useful when the available height varies considerably: there is less space above the higher subfloor. The dry floor grid may fit there, while CircoFloor may suit the lower area.

On a steeply sloping subfloor, the system transition can therefore be in the middle of the same room. Adjust each support point individually and place the transition where the local height accommodates both systems with their boarding. Check the support arrangement and the adjustment screws required; one screw length may not suit every location.

Discover CircoFloor or see our guide to renovation with limited floor build-up height. Always compare the complete floor build-up, including boarding and finish.

How to connect the systems with OSB

1. Establish the shared floor level. Use the laser to mark the desired finished floor level across all zones. Check any doorways and thresholds as well.
2. Allow for the finish and boarding. Subtracting the finish gives you the top of the OSB. Allow 30 mm of OSB in the grid zone and 18 mm in the CircoFloor zone.
3. Adjust both supporting structures. The top of the dry floor grid must be 12 mm below the top of CircoFloor, measured from the same horizontal reference. Measure each system height from its own subfloor.
4. Lay the first 12 mm OSB layer. This layer goes only on the dry floor grid. Lay and fix it according to the dry floor installation guide. Provide the necessary support right up to the transition.
5. Check the connection to CircoFloor. The top of the first OSB layer should now be level with the top of CircoFloor. Check with a straightedge and laser, and make any corrections before adding more boarding.
6. Lay the upper 18 mm OSB layer. Run it across both zones, staggering its joints relative to the lower layer. Use the correct fixing method for each zone and observe the specified edge distances.

The connection is made through the boarding; the dry floor grid does not click directly into CircoFloor. For support, fixings, board joints and edge distances, consult the dry floor installation guide, CircoFloor installation guide and your OSB manufacturer’s instructions.

Fictitious calculation example: 100 and 180 mm

Suppose you have 100 mm to the desired top of the OSB in zone A and 180 mm in zone B. These zones may be in one room or in adjoining rooms. Underlay and floor covering are not included.

Example build-up to the top of the OSB, excluding underlay and floor covering

Component	Zone A	Zone B
Available height to top of OSB	100 mm	180 mm
System	Staenis dry floor grid	CircoFloor
Adjusted system height	70 mm	162 mm
First OSB layer	12 mm	—
Continuous upper OSB layer	18 mm	18 mm
Total build-up to top of OSB	100 mm	180 mm

The subfloor in zone B is 80 mm lower. In A, the calculation is 70 + 12 + 18 = 100 mm; in B, it is 162 + 18 = 180 mm. Both OSB surfaces finish level. The top of CircoFloor is therefore 12 mm higher than the top of the grid.

The 70 mm grid height is within the 45–90 mm range in the dry floor guide. For CircoFloor at 162 mm, use the long adjustment screws: according to the CircoFloor specifications these allow heights of 147–218 mm. The short screws reach 158 mm and are not sufficient here. These system heights exclude boarding, underlay and floor covering.

Practical points to check

• Subfloor and moisture. Work on a stable, load-bearing subfloor. Choose the membrane or vapour control layer to suit residual moisture and the complete build-up, following the installation guides.
• Support. Support the boarding adequately on both sides of the transition. Avoid any unplanned unsupported span.
• Insulating fill. EPS beads and cork granules can fill and insulate the space. The supporting structure and boarding carry the floor; the granules do not replace structural support.
• Boarding and finish. Match the board specification and loading to the installation guides and the CircoFloor build-ups. This OSB example is not automatically a suitable build-up for tiles.
• Doors and thresholds. Before installation, check the clearance under doors and the connection at thresholds, allowing for all finishing layers.

Frequently asked questions

Can I combine CircoFloor and the Staenis dry floor grid?

Yes, between rooms or within a single room with a steeply sloping subfloor, provided the build-up heights are suitable. The OSB boarding forms the connection: 12 + 18 mm above the dry floor grid and 18 mm above CircoFloor in this example.

Why must the dry floor grid be set 12 mm lower?

The first OSB layer is 12 mm thick. Setting the top of the grid 12 mm below the top of CircoFloor brings the first board layer and CircoFloor to the same horizontal level.

Can the OSB run continuously within a room or between rooms?

Yes, the upper 18 mm layer can cross the system transition if it is adequately supported. The transition does not have to be in a doorway. Existing structural joints and the requirements for the OSB and floor covering still determine where joints or transition profiles are needed.

How do I calculate the height when the floor covering is still to be laid?

Subtract the underlay, floor covering and any additional layers from the desired finished floor level. This gives you the top of the OSB. For this example, subtract a further 30 mm for the dry floor grid and 18 mm for CircoFloor.