Walk almost any warehouse and look at the saw-cut joints. In a young building they are neat, clean lines. In a busy one they are chipped, crumbling, full of dirt and lined with black rubber. Those battered edges are not just an eyesore. They are a maintenance cost, a safety issue for forklift operators and a source of dust and damage to wheels and loads. They are also largely preventable. Request a free estimate to discuss your project.
This article explains why joints exist, why they fail under forklift traffic, how filling protects them and what the process looks like. It supports our polyurea joint filling service page and our guide to forklift safety and floor markings.
Why Concrete Floors Have Joints
Concrete shrinks as it cures and dries, and it shrinks and expands with temperature. If a slab had no joints, it would crack in random places. Saw-cut control joints are grooves cut into the slab shortly after it is poured to create a weak line where cracking occurs in a straight, planned way. Construction joints mark the edges of separate pours, and isolation joints separate the slab from columns and walls.
Joints are therefore not defects. They are part of a well-designed slab. The problem is what happens to them later.
How Forklifts Damage Joints
Forklifts and pallet jacks often have hard, narrow wheels carrying heavy loads. When a wheel crosses an open joint, it drops slightly into the gap and strikes the far edge. Each pass chips off a bit of concrete. Over months, the joint edge crumbles and widens, a process known as spalling. The damage is worst where traffic is heaviest, such as aisles, dock approaches and turning areas.
- Wheels bounce over the joint, shaking loads and the operator
- Debris collects in the damaged joint and creates more wear
- Edge damage creates trip hazards and uneven surfaces for walkers
- Spalls grow and can spread into the slab
- Painted lines and floor coatings crossing the joint break up
- Vibration and shock increase wear on the equipment itself
What Joint Filling Does
A joint filler supports the edges of the joint so wheels roll across rather than drop into the gap. It also keeps debris out and, in some applications, helps protect the joint from moisture and contamination. For forklift traffic, semi-rigid fillers such as polyurea are widely used because they are hard enough to support the edges and flexible enough to allow small movements in the slab.
It is important to note that fillers are matched to the joint and the use. A rigid epoxy filler can crack when the slab moves, and a very soft sealant will not support the edges under heavy wheels. Selecting the right material is part of the job, and the manufacturer’s data sheet sets the limits for joint movement and use.
Filling early saves repair later. A joint that is filled when the edges are still sound is a quick, inexpensive job. A joint that has been allowed to spall badly needs edge repair first, and that takes longer and costs more.
Timing in a New Slab
Joints open as a slab dries and shrinks, much of it in the first months. Filling too early means the joint may widen later and the filler can be stressed or pulled away. Filling too late leaves the edges unprotected while the facility is in use. Guidance from industry bodies such as the American Concrete Institute discusses joint behaviour and timing, and your slab designer or engineer can recommend the right moment for your building. A common approach is to fill after most shrinkage has occurred and to revisit joints that move later.
The Joint Filling Process
1. Assessment
We inspect the slab and the joints, identify spalled edges, active cracks and areas of heavy traffic. We note the joint width and depth, and check for existing fillers or sealants.
2. Cleaning the Joint
Old filler, dirt and debris are removed, often with a specialized saw, router or grinder and vacuum, until the joint walls are clean, sound and dry. A clean joint is essential for the filler to bond and perform.
3. Repairing the Edges
Spalled or crumbling edges are cut back or repaired with suitable materials so the filler has a solid surface to support it. Our concrete repair team handles this step.
4. Installing the Filler
The joint is filled in a continuous pass, to the specified depth and level with the surface, using the filler recommended for the use. Polyurea fillers cure quickly, which minimizes downtime.
5. Finishing and Handover
Excess material is trimmed flush, the area is cleaned and cure times are confirmed. We explain when the area can return to forklift traffic.
Joint Filling and Floor Coatings
If a floor is being coated, joints need a plan. Coating over an open joint without treatment can lead to cracking along the line as the slab moves. Joints are typically filled, or detailed so they can move, and the coating is carried across or cut at the joint, depending on the design. Doing joint filling and coating together avoids rework and gives a consistent finish. Our warehouse epoxy flooring page explains how joints fit into a complete floor system.
Signs Your Joints Need Attention
- Chipped or crumbling edges along saw cuts
- A noticeable bump or rattle when forklifts cross a joint
- Debris and dirt packed into joints
- Cracks branching from joints into the slab
- Old filler that has dried, cracked or pulled away
- Worn or broken floor markings where lines cross joints
Cost and Value
Joint work is one of the better-value maintenance tasks in a warehouse. It protects the slab, reduces wear on forklifts and loads, improves operator comfort and makes the floor safer and cleaner. Spalling is progressive, which means every month of delay increases the repair needed. Our epoxy flooring cost guide explains why preparation and repairs belong in any floor plan.
Questions to Ask a Contractor
- Which filler will you use, and why is it suited to my traffic and joint movement?
- How will you prepare the joints, and how will damaged edges be repaired?
- How long will the work take, and when can forklifts return?
- Do you recommend joint filling before or together with a floor coating?
- How will joints be inspected and maintained over time?
Common Mistakes with Joints
- Using a filler that is too soft or too rigid. A soft sealant will not support wheels, and a rigid one can crack when the slab moves.
- Filling over dirt or old filler. The new material cannot bond to a contaminated joint.
- Ignoring spalled edges. Filler cannot hold on crumbling concrete, so edges need repair first.
- Filling too early and too deep. Joints that are still opening can pull away from filler placed before the slab has stabilized.
- Coating over open joints. The coating will crack along the line and the repair will fail.
- Neglecting maintenance. Filled joints still need inspecting, and small gaps repaired before they grow.
Joint Types You Will Meet in a Warehouse
Not every line in a slab is the same. Saw-cut control joints are the most common and are the main target of filling. Construction joints sit at the edge of pours and may carry dowels to transfer loads. Isolation joints separate the slab from columns and walls and are often left flexible for movement. Cracks that have opened over time are different again. Each type has its own movement and its own appropriate treatment, which is why an assessment before filling matters.
Why you can rely on this guidance. Supreme Epoxy is a commercial, industrial and residential flooring contractor established in 2019, WSIB and business insured, with a 4.9 out of 5 rating from 117 Google reviews. We install the floors we write about, including warehouses completed in as little as three days and overnight installs for operations that cannot stop. This article is general information, not engineering or legal advice. We fill joints in warehouses and industrial floors and plan the work around operations to keep downtime short. Every site is different, so confirm requirements for your own space.
Standards and Sources
We refer to these public sources when we plan joint work. Check the current version of each before relying on it.
- American Concrete Institute, ACI 302.1R (Guide to Concrete Floor and Slab Construction) and ACI 360R (Guide to Design of Slabs-on-Ground): industry guides on joints, shrinkage and slab performance
- OSHA 29 CFR 1910.176(a), Handling materials: aisles and passageways must be kept clear and in good repair, with safe clearances for mechanical handling equipment
- Occupational Health and Safety Act (Ontario) and O. Reg. 851, Industrial Establishments: employer duties for safe workplaces
- Joint filler manufacturer technical data sheets: the final word on product use, cure times and joint movement limits
Product performance and slab behaviour vary, so always follow the filler manufacturer’s instructions and the guidance of your slab designer or engineer where joints are structural.
Book a Joint Inspection
If your joints are chipped, dirty or noisy under forklifts, we can inspect them and recommend repairs. Book a free site visit and we will walk the floor, assess the joints and give you a written plan for repair and filling.
