How to choose an expansion joint cover: six questions to answer first

An expansion joint cover closes the gap between two parts of a building that are built to move independently, and it has to keep closing that gap while they move. Most selection mistakes happen because a cover is chosen from a picture before the joint itself has been described. Answer the six questions below first and the choice usually comes down to two or three systems.

1. Where is the joint?

A floor joint is walked or driven over; a wall or ceiling joint is not, but it is seen, and it often has to follow a corner or meet a floor joint. Roof and podium joints sit above occupied space, so water is the main risk. Start in the matching range:

• Floors: interior floor joints, car park and parking deck joints, landscaping joints
• Walls and ceilings: interior wall joints, external wall joints, ceiling joints
• Roofs: roof expansion joint covers

2. How wide is the gap?

Use the nominal joint width: the width of the gap as designed, at the time of installation. On every Genotek product page this is the joint width column of the profile specifications table, and each model is made in a set of sizes, one system drawing per size. The Z1000, for example, is listed in 50 mm and 75 mm joint widths. If the gap on site differs from the drawings, measure it and use the measured width.

3. How much does it move, and in which directions?

Genotek lists movement as a percentage of the nominal joint width. The Z-1000-50 is listed at ±25 %: on a 50 mm joint that means the gap may close to 37.5 mm and open to 62.5 mm while the cover keeps working. Compare that range with the movement your structural engineer expects, not with the gap alone.

The direction matters as much as the amount. Thermal movement is mostly opening and closing across the joint, repeated daily and seasonally. Seismic joints also see shear along the joint and vertical displacement, and the cover must return to position afterwards. For those, start in the seismic and large span range and send us the movement figures for each direction.

4. What crosses it?

Each product page states the traffic the system is meant for, using the same labels as the Product Finder: people, cars, forklifts; on the product cards, pedestrian, light vehicle or heavy vehicle. Choose from systems listed for your traffic, and ask us when the load is unusual (forklifts, service vehicles, point loads from equipment) rather than reading more into a label than it says. The pedestrian, vehicular and heavy duty ranges group the systems this way.

5. What finish surrounds it, and how should it look?

• Recessed or surface mounted. A recessed cover sits in a recess (blockout) in the slab and finishes flush with the floor; it has to be planned before the screed or finish goes down. A surface-mounted cover is fixed on top and suits retrofit work.
• Visible or hidden fixings. Product pages state which one a system uses.
• Sightline. The visible width of the cover, listed in the profile table. Pan-type covers accept the adjacent floor finish, such as tile or stone, so that less aluminium shows.

6. Must it seal against water or fire?

A joint in a roof, podium, car park or wet area needs a watertight system, not only a cover: see watertight floor joints and our guide to how watertight joint covers keep water out. A joint that passes through a fire-rated floor or wall needs a fire barrier in the joint as well as the cover: see expansion joint covers with a fire barrier and tell us the rating the wall or floor carries.

Putting it together

With these six answers, the Product Finder filters the range by gap size, load type, movement, surface, fixing, watertightness and budget. For a full project, send us the joint schedule or drawings through the contact page or at support@genotek.global, and our engineers will propose a system for each joint.