BULDX / Structural Movement

Expansion joint selection: gap, movement and traffic

BULDX product guides5 October 20262 min read

Select an expansion joint system from the structural gap, the required movement and the traffic crossing it. The visible cover width is not the same measurement as the joint opening.

AI-generated application context: Expansion joint selection: gap, movement and traffic — APPLICATION ILLUSTRATIONAI-generated application illustration for this guide. Not a completed BULDX project or an installation drawing.

Selection considerations

Obtain the engineer's movement requirements and identify the expected installation condition. Compare opening and closing capacity separately; a catalogue may list positive and negative movement as different values. Check whether vertical or lateral displacement also needs to be accommodated.

Coordinate the system with the finished floor build-up, support edges and anchorage. Trolleys, pallet trucks and vehicles introduce different crossing conditions. Keep the design movement separate from appearance preferences during shortlisting. A wider-looking cover is not evidence of greater movement capacity, and a matching gap dimension alone does not establish suitability.

Before you specify or order

Record nominal gap and movement separately
Identify crossing traffic
Check depth and support detail

Relevant BULDX catalogue examples

These records illustrate the product types discussed. Compare the full specifications before selecting; listing here does not establish project suitability or make the items interchangeable.

BULDX catalogue illustration of 100 mm Under-Floor Expansion Joint - Type 1, code BDX-EJ-UF-1-100 — CATALOGUE REFERENCE`BDX-EJ-UF-1-100` · Product geometry from the catalogue; a family illustration may be shared by variants. Consult the selected technical documents for dimensions and the approved fixing detail.

Product and code	Selected catalogue fields
`BDX-EJ-UF-1-100`100 mm Under-Floor Expansion Joint - Type 1Under-Floor Joints	Nominal joint width 100 mm Movement capability ±14 mm Profile height 17 / 30 / 50 / 65 mm Standard length 3 m Material Aluminium / EPDM
`BDX-EJ-TF-1-100`100 mm Top-Floor Expansion Joint - Type 1Top-Floor Joints	Nominal joint width 100 mm Movement capability ±14 mm Profile height 17 mm Standard length 3 m Material Aluminium / EPDM
`BDX-EJ-UF-2-100`100 mm Under-Floor Expansion Joint - Type 2Under-Floor Joints	Nominal joint width 100 mm Movement capability ±18 mm Profile height 15 / 41 mm Standard length 3 m Material Aluminium / EPDM

Browse the complete Structural Movement catalogue

Common question

Can cover width be used as the joint gap?

No. Use the labelled gap dimension and the section drawing for the selected system.

References and scope

BULDX catalogue: Structural Movement

Product fields are from the BULDX catalogue. Confirm the current selected drawing, supporting performance documents and approved project detail before ordering. External references, where listed, provide background guidance and do not certify these products.