Roadbase for a Carport

Building a Foundation for Your Carport

A carport foundation needs to handle regular vehicle traffic while providing a level, stable base for the structure above. Whether you're finishing with concrete, pavers, or leaving the roadbase exposed, the prepared sub-base is critical for long-term performance. A single-car carport measuring 6 metres by 3 metres requires approximately 2.7 cubic metres of DGB20 roadbase at 150mm depth. This comes to around 4.9 tonnes, a straightforward bulk delivery for most suppliers.

The standard 150mm depth provides adequate support for cars and light vehicles parking regularly. If you'll be parking heavier vehicles like four-wheel drives, caravans, or boats on trailers, consider increasing to 200mm. The extra material costs relatively little compared to fixing a subsiding carport floor later.

Carport Floor Options

The roadbase layer forms the foundation regardless of your final surface choice. Compacted roadbase alone creates a serviceable floor that drains well and resists dust, though it can track into adjacent areas. A concrete slab over roadbase provides a clean, permanent surface that's easy to sweep and hose down. Pavers over roadbase and sand offer an attractive middle ground with good drainage between the joints. Each option requires the same quality base preparation.

Integration with Driveway

Most carports connect to an existing or new driveway, and the base preparation should be coordinated between these areas. Ensure the carport floor sits at the correct height relative to the driveway surface, typically level or very slightly higher to prevent water pooling. The roadbase layers should meet and compact together without a distinct boundary that could cause differential settling. Planning this connection before you start excavation prevents problems with water drainage and transitions between surfaces.

Planning a driveway as well? Our driveway calculator covers typical driveway dimensions. Use our main roadbase calculator for custom sizes.