COBRA SPIRAL® Foundation Screw
An Easy, Economical, and Environmentally Friendly Alternative to Concrete Foundations
A Solution: Practical & Ecological
The SPIRAL foundation screw is a galvanized steel pile with a thread designed to be driven into the ground and firmly anchored. It allows for the installation of a perfectly stable and level wooden or aluminum structure capable of supporting heavy loads. Installation is simplified due to the possibility of adjusting and correcting imperfections.
The foundation screw is suitable for all kinds of installations, including terraces, swimming pools, jacuzzis, carports, and shelters. Available in several sizes and for different uses, it addresses the need to correct steep slopes, raise structures, or create different structural levels without complicating construction. This solution is an ideal alternative to creating a concrete slab.
It offers less expensive, less time-consuming foundation work, which preserves the garden and encourages soil drainage. The nature of the soil will determine the type of screw and its correct installation.
Visual Description: A cross-section view of soil demonstrating the installation of SPIRAL® Foundation Screws to support a wooden decking structure. The screws are shown anchored deep in the ground, with joists and beams attached to their heads, creating a stable platform above the soil.
All You Need to Know
- Durable - Galvanised steel
- Robust - Body diameter 60 mm
- 120 mm diameter head for a variety of brackets
- Firm anchoring - 75 mm thread
- Resistance to tearing
- Pressure resistance
- Penetrating tip
Visual Description: Detailed technical drawings of the SPIRAL® Foundation Screw, showing its overall length (1200 mm), body diameter (60 mm), head diameter (120 mm), thread details, and specific dimensions. A top-down view shows the bolt pattern on the head.
The Range: SPIRAL SCREW
G800, G1200 and G1500 Screws for Firm Ground and Backfills
Model Numbers: (FD1577-1578-1806 / NL2804-2805-2806)
- Galvanised steel
- 3 sizes available: 800, 1200 and 1500 mm
- 60 mm diameter
- Minimum burial depth of 70 cm (80 cm for the G1500)
Load Capacity and Floor Area Data
| Consistency | Maximum load per screw (N) | Maximum floor area per Screw (m²) | Solicitation 1 of DTU 51.4 | Solicitation 2 of DTU 51.4 |
|---|---|---|---|---|
| Very soft | 1395,15 | 0,40 | 0,56 | |
| Soft | 2172,98 | 0,62 | 0,87 | |
| Farm | 4432,38 | 1,27 | 1,77 | |
| Rigid | 8870,93 | 2,53 | 3,55 | |
| Very rigid | 17735,69 | 5,07 | 7,09 |
| Consistency | Maximum load per screw (N) | Maximum floor area per screw (m²) | Solicitation 1 of DTU 51.4 | Solicitation 2 of DTU 51.4 |
|---|---|---|---|---|
| Very soft | 2417,55 | 0,69 | 0,97 | |
| Soft | 3765,39 | 1,08 | 1,51 | |
| Farm | 7680,53 | 2,19 | 3,07 | |
| Rigide | 15371,77 | 4,39 | 6,15 | |
| Très rigide | 30732,83 | 8,78 | 12,29 |
Visual Description: Images of COBRA G800, G1200, and G1500 SPIRAL® Foundation Screws, illustrating their different lengths and thread designs.
S1200 Screw for Sandy & Soft Floors
Model Numbers: (FD1807 - NL2808)
- Design suitable for soft surfaces, especially sand
- Enhanced resistance to tearing
- Length 1200 mm
- Minimum burial depth of 80 cm
Load Capacity and Floor Area Data
| Consistency | Maximum load per screw (N) | Maximum floor area per screw (m²) | Solicitation 1 of DTU 51.4 | Solicitation 2 DTU 51.4 |
|---|---|---|---|---|
| Very loose | 281,69 | 0,08 | 0,11 | |
| Soft | 2213,29 | 0,63 | 0,89 | |
| Moderately dense | 3712,93 | 1,06 | 1,49 | |
| Dense | 8201,78 | 2,34 | 3,28 | |
| Very dense | 13123,86 | 3,75 | 5,25 |
Visual Description: Image of the COBRA S1200 SPIRAL® Foundation Screw, highlighting its design for soft ground conditions.
Screw P800 for Posts
Model Numbers: (FD1808 - NL2807)
- Designed for post installation
- Crosspiece designed for increased resistance to lateral forces
- Length: 800 mm
Load Capacity and Floor Area Data
| Consistency | Maximum load per screw (N) | Maximum floor area per screw (m²) | Sollicitation 1 du DTU 51.4 | Sollicitation 2 du DTU 51.4 |
|---|---|---|---|---|
| Very soft | 1395,15 | 0,40 | 0,56 | |
| Soft | 2172,98 | 0,62 | 0,87 | |
| Farm | 4432,38 | 1,27 | 1,77 | |
| Rigid | 8870,93 | 2,53 | 3,55 | |
| Very rigid | 17735,69 | 5,07 | 7,09 |
Visual Description: Image of the COBRA P800 SPIRAL® Foundation Screw, designed for post installation.
The Accessories: SPIRAL
Support for Joists
Model Numbers: (FD1809 – NL2810)
- L-shaped support for the support and fastening of joists or beams
- Lateral and axial adjustment
- Adjustment threaded rod, 200 mm in length
- M16 nut
Visual Description: Two L-shaped metal brackets designed to attach joists or beams to foundation screws.
Multi-Purpose Support
Model Numbers: (FD1221 – NL2618)
- 90 x 90 mm square support
- Multiple fixing options
- Adjustment threaded rod, 200 mm in length
- M16 nut
Visual Description: A flat metal plate with a central threaded rod, designed for versatile mounting.
Post Supports
Model Numbers: (FD1901 – NL2864 / FD1902 – NL2865)
- U-shaped post support
- 2 sizes 90 x 90 and 120 x 120 mm
- Height 150 mm
- Thickness 3 mm
Visual Description: Two U-shaped metal brackets designed to hold posts.
Leveling Correction Disk
Model Numbers: (FD1904 – NL2866)
- 3 threaded rods suitable for the foundation screw head
- 3 M12 nuts for easy and precise adjustment
- Thickness of the disk: 4 mm
- Central opening for the installation of SPIRAL accessories
Visual Description: A circular metal disk with holes for threaded rods and nuts, used for leveling. Also shows nuts and threaded rods. The diagram illustrates how these components connect to a foundation screw and a post support.
Adapter for Impact Wrench
Model Numbers: (FD0616 – NL2385)
- Ensures the connection between the installation tool and the foundation screw.
- Central fastening with a single screw for easy, and secure assembly.
- 6 peripheral tabs.
- Integrated bubble level to check the verticality of the installation.
- Hexagonal central head M41
Visual Description: Several views of a metal adapter designed to connect an impact wrench to a foundation screw, featuring a bubble level for vertical alignment.
Manual Screwing Bar
Model Numbers: (FD0615 – NL2384)
- Manual screwing kit for anchoring the foundation screw manually.
- Consists of a pre-drilled rod for adjusting the height of the bar as screwing progresses
- Span of 160 cm and thickness of 3 mm, providing a lever arm for easy tightening
- 3 bolts + nuts to secure the tool on the screw.
- The bar can be lifted during screwing to facilitate the pushing motion
Visual Description: A long metal bar with handles and a mechanism to attach to a foundation screw, used for manual installation. Also shows the components of the bar.
Installation of the Screw
The ease of driving in the screw depends on following the installation steps, the equipment used, and the nature of the soil.
Assembly of the Screw and the Drilling Tool
- Securely couple the drilling tool with the head of the foundation screw. Use the M41 adapter for the use of an impact wrench (1).
- Perform the necessary rotations to reach the desired anchoring depth (minimum burying of 70 cm, 80 cm for G 1500 and S 1200 screws).
- Remove the tooling from the head of the foundation screw and install the required screw head (2).
Installation with an Impact Wrench
Visual Description: Three steps illustrating the connection of an impact wrench with an M41 adapter to the foundation screw.
Note (1): When using an impact wrench, the M41 adapter is required. Subjected to vibrations and significant stress during drilling, it must be assembled with sufficient torque. It is highly recommended to use an impact wrench to securely tighten the central clamping nut.
Installation with the Manual Tool
Visual Description: Three steps illustrating the use of the manual screwing bar.
Note (2): Screw the required head according to its use, whether for joist support or flat support, and precisely adjust the threaded rod to the desired height. Adjustable from 0 cm to a maximum of 15 cm.
Installing the Screw
Marking
Marking is crucial as it allows determining the precise locations of the necessary screws and ensures the alignment of the structure to be fixed.
- Establish a reference line to align one side of the construction to be carried out.
- Lay the geotextile fabric.
- Establish points of perpendicularity to this reference line for creating right angles.
- Stretch a string between the markings.
- Place drilling markers for the screws based on the layout plan of the structure to be built, following the recommended spacing between support points.
Visual Description: Illustrations showing how to mark out a construction area using reference lines and measurements for joist spacing.
Ground Preparation
The creation of pilot holes and lubrication is essential to aid in the implementation of the foundation screw.
- The pilot hole, whether manual or mechanical, will check the nature of the soil in depth and then facilitate the penetration of the screw into the ground. Use a crowbar and a mallet or a drill with a bit of at least 35 mm in diameter. Create a hole with a depth less than the length of the screw that will be buried. Ensure beforehand that there are no cables, pipes, etc., in the location where the screws will be positioned.
- Lubrication with water, especially in hard or very dry soil, will allow for easier drilling and put less strain on the equipment used.
- Initially engage the foundation screw by hand in the pilot hole to start the burying phase.
Visual Description: Illustrations showing manual/mechanical pilot hole creation, lubrication with water, and initial screw engagement.
Necessary Equipment: Tape measure - Chalk line - Ruler - Level - Mallet - Stakes - Crowbar and mallet or Drill and minimum 35 mm drill bit - Watering can - Screwdriver bar or Impact wrench - Impact drive
Implementation of the Screw
Caution: The use of foundation screws requires checking for the absence of obstacles at the drilling points.
Steps
- Step 1: Installation of foundation screws
- Step 2: Placing the joists
- Step 3: Double joisting
- Step 4: Placing the planks
Visual Description: Four steps illustrating the implementation process: 1. Installation of foundation screws. 2. Placing the joists. 3. Double joisting. 4. Placing the planks.
