A visually small post change can alter beam span substantially.
OUTDOOR ARCHITECTURE · SPANS
Louvre pergola span and post planning.
The number and location of posts is a structural and architectural decision. It should be resolved before glazing, doors, screens, furniture and drainage are locked.
SHORT ANSWER
Start with required clear openings and bay logic, then validate the structure.
Mark the areas that must stay post-free, the acceptable post zones, building connection, roof spans, site levels and drainage paths. Then qualify an exact ARKEN or CADARN system around those constraints.
KEY PROJECT POINTS
What should drive the decision.
These are project inputs, not substitute engineering or automatic product approvals.
Wall mounting transfers load into an existing building interface.
Multi-bay layouts may be better than forcing one oversized clear span.
3 m CADARN posts can help with slopes/raised slabs and are cut on site where used.
Post locations also control screen/door openings.
Downpipes/drainage often run through or beside posts.
Draw the no-post zones
Doors, views, vehicle routes, pool edges, dining layouts and circulation should be marked before the pergola structure is set out.
Use bays intelligently
Dividing a larger roof into logical bays can improve structure, drainage and accessory integration while keeping the architecture coherent.
Coordinate levels
Sloping ground, raised slabs, decks and steps can require longer posts, cut-to-height installation and careful gutter/downpipe falls.
Verify the building interface
Wall-mounted systems need local review of substrate, fixings, waterproofing and load transfer into the existing structure.
PROJECT INPUTS
What to have ready before asking for the exact system.
A stronger brief shortens the gap between product interest and a useful technical/commercial response.
Overall width/projection
Required clear openings
Acceptable post zones
Bay count
Wall/freestanding
Building substrate
Finished floor levels
Post height
Wind/site exposure
Screens/doors
Drainage route
Local foundation design
EVIDENCE BOUNDARY
Do not publish a maximum span without the exact profile, loading and support condition.
Span depends on selected profiles, bay geometry, support condition, wind/snow criteria, accessories and project engineering. Use exact-system data and local structural review.
FAQ
Questions project teams usually need answered.
Can a 6 × 4 m pergola always use four posts?
Not universally. Post/beam arrangement depends on the exact system and project loads.
Why use more than one bay?
Multi-bay layouts can improve span, drainage, accessory integration and overall structural efficiency.
Can posts be cut on site?
CADARN 3 m aluminium posts can be supplied full length for site cutting where that configuration is selected.