Construction Products
FAQ
FREQUENTLY ASKED QUESTIONS
Technical questions about ventilated crawl spaces, lightweight slabs, permeable paving and below-ground wall protection systems
Project For Building systems for the construction industry integrate structural, drainage and protection functions into technical solutions made from recycled plastic.
This section brings together the most frequently asked questions about ventilated crawl spaces, lightweight bidirectional slabs, permeable paving and below-ground wall protection systems.
The answers have been prepared by our technical team to support designers, structural engineers and construction companies.
DRAIN FLOOR:
green roofs
Recycled plastic element for green roofs and roof gardens
DRAIN FLOOR is a prefabricated element made of recycled plastic for the construction of green roofs (extensive and intensive).
It combines three functions within a single layer:
- protection of the waterproofing membrane;
- drainage of rainwater;
- water storage to support vegetation during dry periods.
By integrating these functions into a single element, DRAIN FLOOR allows for more precise control of the roof's hydraulic and mechanical performance.
DRAIN FLOOR is typically installed on flat roofs with slopes between 1% and 4%, ensuring proper rainwater drainage towards the roof outlets.
For sloped roofs, additional anchoring systems must be provided to prevent the upper layers from sliding.
DRAIN FLOOR creates a separation layer between the waterproofing membrane and the overlying soil.
Its 6 cm support feet distribute loads evenly and reduce the risk of:
- punctures and abrasion during installation and maintenance;
- localized compression caused by the overlying layers.
This helps extend the long-term durability of the waterproofing system.
The module geometry creates a continuous cavity that allows excess water to flow towards the drainage points.
The height of the support feet helps ensure:
- rapid drainage of rainwater;
- reduced water stagnation;
- maintenance of a functional air layer beneath the soil.
Yes. UNI 11235:2015 identifies DRAIN FLOOR as a prefabricated water storage element that also performs protection and drainage functions.
The standard requires the water storage element to provide:
- at least 60% free air circulation from the drainage layer to the growing medium;
- an air gap between the free water level (when present) and the filter layer equal to at least 30% of the thickness of the water storage layer, with a minimum of 1 cm, to prevent deterioration of the root system.
The air layer does not necessarily have to be integrated into the module itself, but it must always be present between the water storage element and the drainage layer.
The water storage volume may be partially filled with a porous material (such as perlite) up to 1 cm above the upper level of the module.
A suitable filter geotextile must be placed between the perlite and the growing medium to prevent fine particles from entering the air layer.
No standard limit is specified. The amount of water to be stored depends on the design strategy, the type of substrate and vegetation, as well as the climatic conditions of the site.
The module is made of recycled polyolefins (PP-PE), a material that is:
- resistant to weathering;
- rot-proof and dimensionally stable over time;
- suitable for long-term roofing applications.
It is Plastica Seconda Vita (Plastic Second Life) certified, helping to meet the requirements of the Minimum Environmental Criteria (CAM).
Modules
GRANCHIO / MINIHERCULES / HERCULES / SUPERHERCULES / EVEREST
Recycled plastic elements for ventilated crawl spaces
A ventilated crawl space creates a continuous cavity between the ground and the building, interrupting capillary rising damp and enabling natural ventilation beneath the foundation slab.
This air cavity performs specific technical functions:
- it blocks rising damp;
- it promotes radon gas dispersion;
- it helps stabilize the thermo-hygrometric conditions of indoor spaces.
It is therefore a proven solution for improving building healthiness and durability, in both residential and industrial applications.
To achieve effective natural ventilation, it is necessary to create a difference in both temperature and height between the air intake and outlet points.
The air intake openings should be positioned on the cooler side of the building (north-facing), while the air outlet openings should be placed on the warmer side (south-facing) at a higher elevation. Pipes exposed to sunlight heat up, creating an upward airflow that naturally activates air circulation within the crawl space.
During the design phase, the following is recommended:
- alternate air intake and exhaust openings every 4–5 metres;
- use ventilation pipes with a diameter between 80 and 120 mm;
- connect the different foundation compartments to ensure continuous airflow throughout the entire crawl space.
A ventilated crawl space consists of a grid of recycled plastic permanent formwork units (Granchio, the Hercules line and Everest) that define the geometry of the cavity.
The formwork units do not have a structural load-bearing function, but they must ensure adequate resistance during installation. Once installed, they must be walkable and able to withstand the weight of the operator, reinforcement and tools required for casting the concrete slab, with an indicative resistance of at least 150 kg.
The final load-bearing capacity of the system depends on the overall design and on the combination of:
- soil type;
- sub-base characteristics;
- formwork height;
- thickness and reinforcement of the upper slab.
This integration determines the actual strength of the finished floor, which may reach values suitable even for industrial and logistics applications with high loads.
A ventilated crawl space is a versatile solution and can be used in most types of buildings, including:
- residential buildings;
- commercial buildings;
- public infrastructure;
- industrial and logistics facilities.
When properly designed, it is suitable for both uniformly distributed loads and high concentrated loads.
The formwork units are installed dry, making the process quick and easy. The lightweight, easy-to-handle elements are laid in horizontal rows, starting from one corner of the foundation and progressing across the entire area.
Each formwork unit features directional arrows indicating the correct orientation, ensuring consistent and continuous overlapping throughout the entire crawl space.
In most cases, no special elements are required.
Only when the crawl space slab and side edge beams are poured at the same time is it necessary to use specific L-shaped closure profiles, available for the different heights of the Granchio modules. These profiles prevent concrete from entering the cavity.
The formwork units can be cut to size directly on site. The section without legs can be supported against the side edge beam by preparing a simple ledge made from wooden battens or hollow clay tiles fixed to the side beam.
Project For Building’s technical department supports designers with:
- a preliminary calculation report for the floor slab with ventilated crawl space;
- layout of the formwork units on the structural plan;
- accurate quantity take-off of the elements;
- cost estimate for the construction work.
This allows the system to be integrated into the project in a controlled way, with clear quantitative data from the early design stages.
SAFE ROLL:
below-ground waterproofing
HDPE dimpled membrane for below-ground waterproofing protection
SAFE ROLL is a high-density polyethylene (HDPE) dimpled membrane designed to protect the waterproofing of below-ground structures during backfilling operations.
The dimples, facing the wall, distribute soil loads and create an 8 mm air cavity that physically separates the wall from the surrounding ground.
The system can be used:
- in new construction projects;
- in renovation and refurbishment works;
- as a separation layer beneath ground-bearing slabs;
- as a partial replacement for the lean concrete blinding layer.
SAFE ROLL is made of HDPE (high-density polyethylene), a material with excellent chemical and physical stability.
The membrane is:
- resistant to water and microorganisms present in the soil;
- resistant to chemicals and root penetration;
- stable within a temperature range from −40°C to +80°C;
- rot-proof and durable over time.
It does not release pollutants into drinking water.
The dimpled structure provides a compressive strength of 230 kN/m².
This enables the membrane to effectively withstand the pressures exerted by the surrounding soil during backfilling, protecting the waterproofing layer.
SAFE ROLL can be safely used in below-ground structures up to 5 metres deep, depending on the project design conditions.
The membrane is supplied in rolls with:
- variable height from 1 m to 3 m;
- length of 20 m.
It is applied by simply unrolling it in vertical or horizontal strips, depending on the wall geometry.
The dimples must face the wall to ensure proper load distribution and the formation of the air cavity.
SKUDO is a rigid panel that creates a 7.5 cm structural cavity between the soil and the wall, providing robust mechanical protection and greater drainage capacity. It is recommended when a substantial physical barrier between the soil and the waterproofing layer is required.
SAFE ROLL, on the other hand, is an HDPE dimpled membrane with an 8 mm air cavity, designed primarily to protect the waterproofing layer during backfilling by distributing soil pressure without creating significant structural thickness.
The choice between the two systems depends on:
- available installation thickness;
- drainage requirements;
- design conditions and expected loads.
Both systems protect the waterproofing layer, but they differ in their construction approach and performance characteristics.
GREEN PARKING:
driveable permeable paving
Driveable honeycomb system designed to create permeable surfaces while maintaining soil permeability and distributing traffic loads.
GREEN PARKING is a recycled plastic honeycomb grid (40 × 40 × 4 cm) designed for the construction of permeable parking areas and driveable or pedestrian surfaces.
Its honeycomb structure protects the ground from vehicle traffic and parking by distributing loads evenly and preserving the surface. During rainfall, water drains through the openings in the grid, preventing water stagnation and the formation of puddles.
The system makes it possible to create driveable surfaces while maintaining a natural grassed or permeable finish.
Yes.
The material and geometry of the module allow resistance to distributed loads of up to 20 t/m², making it suitable even for heavy vehicle traffic, provided it is correctly installed on a properly designed sub-base.
Proper sub-base preparation is essential to ensure the stability and durability of the system.
The recommended build-up includes:
- a stabilized sub-base, designed according to the expected loads;
- a bedding layer approximately 2 cm thick, levelled to provide a flat surface;
- where required, a geotextile between the sub-base and the bedding layer, particularly on highly permeable soils, to prevent washout.
Once the bedding layer has been prepared, the GREEN PARKING modules can be installed.
The honeycomb structure can be filled with:
- a soil mix (volcanic sand enriched with organic fertilizers) to create a driveable grass surface;
- gravel with a particle size of 0–5 mm to maximize drainage capacity.
The choice depends on the desired final appearance and the site's drainage requirements.
The module is made of recycled PP-PE with high mechanical strength.
The material is:
- resistant to frost, rain, UV rays and temperature variations;
- rot-proof and dimensionally stable over time;
- made of at least 95% recycled plastic.
The percentage of recycled content is certified by the Plastica Seconda Vita mark, helping to meet the requirements of the Minimum Environmental Criteria (CAM).
In addition to its mechanical strength, the interlocking system is designed to ensure long-term stability.
After on-site assembly, the adjoining edges are automatically spaced by approximately 3 mm. This small joint absorbs the thermal expansion of the material, preventing mutual stress between the modules that could cause warping or breakage.
A permeable paving system allows rainwater to infiltrate the ground, reducing the risk of surface water accumulation and easing the load on drainage systems.
Compared with an impermeable surface, it offers several advantages:
- reduces the formation of puddles;
- limits surface runoff;
- allows rainwater to infiltrate directly into the subsoil;
- helps recharge groundwater;
- preserves the natural permeability of the soil;
- maintains a more natural surface appearance.
These characteristics are particularly important in urban environments and newly developed parking areas, where stormwater management is a key design consideration.
In many cities, new developments must comply with hydraulic invariance requirements, meaning they must not increase stormwater runoff compared with the site's natural condition.
SKUDO:
mechanical protection for below-ground walls
Mechanical protection for below-ground retaining walls.
SKUDO is a recycled plastic panel designed for the mechanical protection of the waterproofing layer on below-ground walls.
During backfilling operations, waterproofing systems, such as bituminous membranes, synthetic membranes or liquid-applied products, can be damaged by:
- stones and backfill materials;
- compression caused by soil pressure;
- abrasion or detachment.
The SKUDO panel creates a physical barrier between the soil and the waterproofing layer, helping ensure the long-term durability of the system.
Unlike conventional dimpled membranes, SKUDO does more than create a small air gap: it forms a robust structural barrier between the soil and the wall.
The cavity created between the wall and the surrounding ground is 7.5 cm wide, significantly larger than the less than 1 cm air gap typically provided by dimpled membranes. This creates an air chamber with a capacity of 65 l/m².
This provides:
- greater drainage capacity;
- improved physical separation from the surrounding soil;
- reduced risk in the event of accidental water infiltration from the top edge.
A drainage collector is installed at the base of the wall to direct the collected water away from the structure.
SKUDO is supplied in 59 × 79 cm panels, making them easy to handle on site.
Installation starts at the base of the wall, with the panels placed side by side. The interlocking edge system provides a continuous and secure connection between adjacent panels.
Vertical and horizontal fixing is achieved using anchors inserted through the dedicated slots. At corners, a specific L-shaped profile is used, while the top edge is finished with a double capping profile.
Yes.
The panels, made of recycled plastic, can be easily cut on site using saws or cutters whenever they need to be adapted to specific dimensions to complete the wall covering.
Yes.
The system can be used in both new construction and renovation or waterproofing refurbishment projects for below-ground walls.
Once correctly installed and covered by backfill, SKUDO does not require maintenance. The material used is inert, rot-proof and durable over time.
However, it is essential that the drainage system at the base of the wall — drainage pipe and collector — is properly designed and kept efficient, preventing clogging or blockages.
SUB PRO / SUB ONE formwork systems:
lightweight bidirectional slabs
Systems for the construction of lightweight bidirectional slabs, reducing concrete weight and optimizing structural performance.
SUB PRO and SUB ONE formwork systems are designed for the construction of lightweight bidirectional slabs, suitable for residential and commercial buildings, public works and multi-storey car parks.
The system is particularly suitable when the project requires:
- long structural spans;
- reduced slab thickness;
- lower overall slab weight.
Reducing the weight of a slab means eliminating concrete where it is not required for structural performance while maintaining the necessary load-bearing capacity. This makes it possible, for the same design load, to reduce the slab thickness or, for the same thickness, to achieve longer spans compared with a traditional solid slab.
The reduction in self-weight benefits the entire structural system, potentially reducing the size of beams, columns and foundations, with associated economic advantages.
The smooth soffit also allows the underside of the slab to be finished with a simple skim coat, without the need for thick plaster.
The main difference lies in the formwork configuration and the available heights.
SUB PRO:
- consists of two elements: base + cover;
- each element is available in heights of up to 30 cm;
- when assembled, it reaches heights of up to 60 cm;
- features a closed bottom.
SUB ONE:
- one-piece (monolithic) formwork;
- available in heights of up to 24 cm;
- features an open bottom.
In both systems, the slab is cast in two stages:
- the first pour fills the formwork up to the height of the support legs (or slightly above);
- the concrete pour is completed after the initial setting of the concrete.
This first stage prevents concrete from filling the formwork cavity, even in the open-bottom version.
Design considerations
SUB PRO is also suitable where greater slab depths or more demanding structural configurations are required, such as foundation slabs, thanks to its modular design, which allows heights of up to 60 cm. The combination of the two modules also reduces the inclination of the formwork walls, further minimizing concrete consumption.
SUB ONE is a more compact, monolithic solution designed for slabs up to 24 cm high.
The choice between the two versions does not result in significant structural differences, as the void volumes created by the formwork are very similar.
To ensure proper filling of the lower slab, it is recommended to use concrete with the following consistency classes:
- S4 (fluid);
- S5 (superfluid).
These consistency classes ensure complete and uniform filling of the lower slab during casting.
The support legs raise the void formwork above the soffit of the slab, creating the space required for:
- placing the reinforcement;
- casting the continuous lower concrete slab.
The height of the support legs depends on the structural design requirements, particularly the reinforcement layout and concrete cover. In residential applications, heights generally start from 6–7 cm.
The support legs are integrated into the four corners of every SUB formwork unit.
The formwork height is determined exclusively by structural and design requirements.
As a preliminary guideline, the following can be considered:
- 6–7 cm for the continuous lower concrete slab;
- 6–7 cm for the continuous upper concrete slab;
- the height of the formwork itself.
Starting from the maximum slab thickness defined by the project, the most suitable SUB module height can then be selected. The final choice must always be verified through the structural calculations.
Project For Building has developed SUB DESIGN, a calculation software dedicated to the preliminary sizing of lightweight bidirectional slabs with SUB modules.
The software, available for free download from the company website, allows structural engineers to:
- choose the slab configuration;
- verify performance according to project requirements.
On request, more in-depth technical support is available, including the preparation of project drawings and dedicated calculation reports.
Technical support for designers and construction companies
The Project For Building technical team provides support for:
- structural preliminary sizing;
- build-up verification;
- quantity take-off;
- integration into technical specifications;
- CAM compliance assessment.
For analysis of a specific project, technical documentation can be submitted, such as the structural plan, build-up details and preliminary report.
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CONTACT
Production of innovative products for the construction industry, using recycled and regenerated plastics and complete control of the production cycle.
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Via Fornace, 24050 Mornico al Serio, Bergamo - Italy -
E-mail: info@projectforbuilding.com
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Tel: (0039) 035 4490 440
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Fax: (0039) 035 4490 752
For any inquiries, you can contact PROJECT FOR BUILDING by email or phone, or fill out the form and our team will get back to you.