Reactive & Expansive Soil Solutions


CUPOLEX® is a patented concrete forming system made from 100% recycled plastic. Concrete is placed over the modular dome forms to create floating or structural slabs with an under slab void that results in minimal concrete contact with the soil , provides a capillary barrier against moisture – yet uses less concrete and rebar than a standard slab with equivalent load bearing capacity. The unique patented concrete geometry which Cupolex forms minimizes the contact area on the soil which does not restrain the potential swelling of soils beneath the slab. The minimal concrete in contact greatly reduces the lateral and uplift forces that are produced compared to a conventional slab bearing on the soil throughout the total slab area. The Cupolex slab in contact with the soil ranges from 4% to 10% of the total slab area creating a space into which soil can expand without causing damage.

Cupolex slabs do not restrain uplift forces and furthermore the dead loads of the concrete slab usually are greater than the uplift forces from the soil resulting in protection of the structure. In extreme swelling soil conditions, suspended self-bearing Cupolex slabs would be constructed.


  • Quick and simple to install
  • Minimizes the need for skilled labor
  • Supplied on short lead times
  • Tailored to any type of site requirements
  • Saves aggregate, concrete and steel
  • Speeds construction
  • Lowering building costs
  • Reducing the cycle time of building
  • Maximum control of concrete curing
  • Providing a higher quality floor surface;
  • Solution for Structural Weight Limits
  • Contributing to GREEN or LEED certified building


Traditional old fashioned void forming systems for in-situ ground slabs and beams used on expansive soil sites are increasingly being replaced by Cupolex, a quicker and less labor intensive alternative – A trend that is encouraged by the emphasis on fast track building programs. Reacting to this trend, Cupolex has developed a complete design and supply service for an extensive range of slab formwork systems that can be designed for sites with:

  • Low levels of expansive soils
  • Moderate to high levels of expansive soils
  • Critical and hydrocolapsible soils
  • Low bearing and expansive soils
  • Post tensioned slabs
  • Monolithic slabs

Design & Engineering

We provide PE stamped shop drawings through our engineering partners globally, construction training, and installation observation and we work closely with the design team, the contractor, and the owner to ensure the success of the project.  Each site is different, and working with project partners to find installation solutions that address specific site needs is a part of the service we provide.

To begin using CUPOLEX® for your structural concrete slab design, visit our Getting Started page for a step-by-step road map on using this product.


Please refer to the Cupolex Technical Data Sheet for details of the physical properties of the product range. The appropriate height of Cupolex should be selected based upon the required equivalent void and the maximum load capacity that the slab is required to support. This information is provided in the table below:


Form TypeOverall Form DepthPlan Dimension InstalledConcrete Consumption To Top of DomesClear Void EquivalentDead Load of Concrete Structure to Top of DomesData SheetCAD Block
cm (inch)cm (inch)m3/m2 (cy./sq.ft.)cm (inch)kPa (psf)
WINDI 5-565 (2")56x56 (22"x22")0.008(0.0010)4 (1.57")0.19 (3.96)PDFDWG
WINDI 10-5610 (4")56x56 (22"x22")0.030(0.0036)7 (2.76")0.71 (14.82)PDFDWG
CUPOLEX 9.5-569,5 (4")56x56 (22"x22")0.014 (0.0017)8 (3.15")0.33 (6.89)PDFDWG
CUPOLEX 13.5-5613,5 (5")56x56 (22"x22")0.030 (0.0036)11 (4.33")0.71 (14.82)PDFDWG
CUPOLEX 16-5616 (6")56x56 (22"x22")0.035 (0.0043)14 (5.50")0.83 (17.33)PDFDWG
CUPOLEX 20-5620 (8")56x56 (22"x22")0.035 (0.0043)17 (6.69")0.83 (17.33)PDFDWG
CUPOLEX 26-5626 (10")56x56 (22"x22")0.045 (0.0055)22 (58.66")0.83 (17.33)PDFDWG
CUPOLEX 30-5630 (12")56x56 (22"x22")0.042 (0.0051)26 (10.24")0.99 (20.67)PDFDWG
CUPOLEX 35- 5635 (14")56x56 (22"x22")0.045 (0.0055)31 (12.20")1.06 (22.13)PDFDWG
CUPOLEX 40-5640 (16")56x56 (22"x22")0.060 (0.0073)34 (13.39")1.42 (29.65)PDFDWG
CUPOLEX 45-5645 (18")56x56 (22"x22")0.064 (0.0078)39 (15.35")1.51 (31.53)PDFDWG
CUPOLEX 50-5650 (20")56x56 (22"x22")0.065 (0.0079)44 (17.32")1.53 (31.95)PDFDWG
CUPOLEX 55-7155 (22")71x71 (28"x28")0.069 (0.0080)48 (19.29")1.63 (34.04)PDFDWG
CUPOLEX 60-7160 (24")71x71 (28"x28")0.070 (0.0085)53 (20.87")1.65 (34.46)PDFDWG
CUPOLEX 65-7165 (26")71x71 (28"x28")0.071 (0.0090)58 (22.83")1.68 (35.08)PDFDWG
CUPOLEX 70-7170 (28")71x71 (28"x28")0.073 (0.0095)63 (24.80")1.72 (35.92)PDFDWG
Overall Form Depth cm (inch)Data SheetCAD Block



  • Cupolex-Pontex  Details


Leed Contribution


  • Cupolex Installation Procedure

Technical Reports

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