Every warehouse and factory slab has joints. They are there by design, to control cracking and allow the concrete to move. Left open, though, they become a hazard. Small hard wheels on forklifts and pallet trucks hit the unsupported edges over and over until the concrete breaks away. The joint widens, the bumps get worse, and loads and drivers feel every crossing. This guide covers what is happening and how it is treated.
Types of floor joint
- Saw-cut induced joints: cut into the slab soon after pouring so cracking happens in a straight line.
- Construction joints: where one day’s pour meets the next.
- Movement or isolation joints: around columns, walls and at changes in structure, where larger movement is expected.
Each behaves differently, so the filler or sealant has to suit the joint.
Drawings from the original floor contractor, if you have them, show where each type sits. Without them, the pattern is usually easy to read on site: induced joints in a regular grid, construction joints along pour lines, and isolation joints around columns and walls.
How traffic breaks joint edges
An open joint leaves the top corners of the concrete, the arrises, with nothing supporting them. Each time a hard wheel crosses, it knocks the edge. Over time small pieces chip off. Grit and debris then fill the gap and act like a wedge. The damage grows with every pass, and the joint becomes a trip and impact risk. Vibration through the truck adds to driver discomfort and can unsettle loads.
Filling or sealing: choosing the right product
The right filler or sealant depends on the traffic and the movement:
- In heavily trafficked joints where movement is small, a semi-rigid filler is common. It supports the edges so wheels roll across.
- Where movement is larger, a flexible sealant is used, accepting that it gives less edge support.
- In pedestrian areas, showrooms and retail floors, a trafficable flexible sealant often suits.
Timing matters too. A slab can keep shrinking for some time after it is poured, and some fillers are best installed once most of that movement has happened. Follow the floor designer’s and manufacturer’s guidance.
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If the edges are already damaged
Filling a joint with broken edges rarely lasts. The filler needs solid concrete each side to bond to and to share load. We’ll tell you if the edges need repairing first, before filling or sealing. Catching joints early, before spalling sets in, keeps the job simpler.
Keeping the warehouse running
Floor joint work is usually done in sections, aisle by aisle or bay by bay, so the rest of the building stays in use. Each section needs clearing, then time for the product to cure before traffic returns. Loading bays and main routes can be done in short windows. Phased work can be planned so areas stay in use, and our floor joint sealing page explains how. For wider context, see our industrial units and warehouses page.
A simple inspection routine
Floor joints are easy to check during normal operations. Ask a supervisor to walk the main routes once a month and note:
- joints where filler is missing, sunk or loose
- chipped or broken edges
- debris packed into open joints
- areas where trucks visibly bump or loads shift
Dock levellers, turning areas and routes in front of racking ends usually wear first. Catching these early keeps repairs small and reduces downtime. See our guide to planned sealant maintenance.
Quick answers
Why are some joints sealed and others filled?
It comes down to the traffic and the movement. Semi-rigid fillers support edges under hard wheels where movement is small. Flexible sealants accept more movement but give less edge support.
Can the floor stay in use?
Yes, in most cases. Work is phased by aisle or zone. Each area is closed for the work and the cure time stated for the product, then handed back.
How do I know if my joints need attention?
Look for open gaps, missing filler, chipped edges and debris in the joint, and listen for trucks bumping across. Joints on main routes and at dock doors usually show wear first.
Related services
More advice
- Car Park Expansion Joints: Sealing and Upkeep
- Why Expansion Joints Fail and How to Fix Them
- Movement Joints in Large Tiled Floors
- Planned Sealant Maintenance for FMs
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.