Sealants
Choosing a sealant for industrial floor joints
Forklift traffic, slab movement and cleaning chemicals: the criteria for choosing the right joint filler for a floor.
Short answer
Start by identifying the joint type. Saw-cut joints that carry hard-wheeled traffic such as forklifts need semi-rigid epoxy or polyurea fillers that support the edges. Moving expansion and perimeter joints, and areas with foot traffic, call for an elastic PU sealant. Chemical exposure, joint preparation and timing decide how long it lasts.
1Know the joint type
- Saw-cut (contraction) joints: cut into the slab to control the cracks that concrete shrinkage would cause. They open a little as the concrete shrinks and largely settle over time.
- Expansion joints: allow thermal and structural movement between parts of the building; they move all the time.
- Perimeter and column joints: separate the slab from walls and columns and take their different movements.
- Construction joints: lie between slab sections poured on different days; they often behave like saw-cut joints.
The right filler depends on how much the joint moves and what runs over it. An expansion joint and a saw-cut joint are not filled with the same product.
2Hard-wheeled traffic: support the edges
As the hard wheels of forklifts and pallet trucks hit the joint, the concrete edges break away. A soft, elastic sealant cannot carry the wheel, so the edge is left unsupported. That is why saw-cut joints under hard-wheeled traffic are filled with a semi-rigid epoxy filler or polyurea filler that has a high hardness on the Shore A scale.
These fillers go into the full depth of the saw cut, without a backer rod, and support the edges from below.
3Timing: let the slab shrink first
Semi-rigid fillers take very little movement. If they go in while the concrete is still shrinking, the filler separates from the edges. The general advice is to fill as late as possible after the slab is poured, in most projects several months later. If the area must be used earlier, a temporary solution can go in first and the permanent filler later.
4Moving joints: elastic PU sealant
Expansion, perimeter and column joints move all the time, so they need an elastic sealant that follows the movement. On floors with foot traffic, shopping trolleys or rubber-wheeled traffic, PU sealants with high abrasion and tear resistance are the usual choice. Sealants for pedestrian walkways are classified to EN 15651-4.
In a joint with an elastic sealant, a backer rod sets the depth and prevents three-sided adhesion. Leaving the sealant surface a few millimetres below the floor reduces how often wheels run directly on it.
| Joint and use | Suggested filler | Note |
|---|---|---|
| Saw-cut joint, hard-wheeled traffic | Semi-rigid epoxy or polyurea | Full depth, no backer rod, fill late |
| Saw-cut joint, foot traffic | Elastic PU sealant | With a backer rod |
| Expansion and perimeter joint | Low-modulus elastic PU sealant | Choose by movement capacity |
| Area with chemical exposure | Special chemical-resistant sealant | Check the resistance list in the TDS |
5Chemicals and cleaning
In food, pharmaceutical and chemical plants the floor is washed often and meets oil, fuel, acids or cleaning chemicals. How well a sealant resists them varies widely from product to product. Before choosing, list the chemicals the joint will meet and compare them with the resistance information in the product’s technical data sheet.
Application steps
- Clean the joint
Remove saw dust, loose material and any old filler completely, then vacuum the joint.
- Dry, sound edges
The joint edges must be dry, dust-free and sound. Repair broken edges before filling.
- Primer and backer rod
Apply primer if the product needs it. For an elastic sealant, fit a backer rod of the right diameter.
- Fill and tool
Fill the sealant without gaps and tool the surface by pressing it with a spatula.
- Sealant
- Backer rod
- Concrete
The elastic sealant bonds only to the two sides; the backer rod sets the depth and stops it bonding to the base.
See our Vickers PU Sealant page for moving floor and expansion joints, and this guide for the PU and silicone comparison.
Frequently asked questions
Can PU sealant go into a joint that forklifts cross?
Not in saw-cut joints under hard-wheeled traffic: an elastic sealant cannot support the edge. Those joints take semi-rigid epoxy or polyurea fillers.
When should floor joints be filled?
For semi-rigid fillers, as late as possible, after most of the slab shrinkage has taken place. Elastic sealants follow movement and are less sensitive to timing.
Is a backer rod needed in a floor joint too?
With an elastic sealant, yes: it sets the depth and prevents three-sided adhesion. Semi-rigid fillers go in at full depth without one.
Should the sealant be flush with the floor?
With an elastic sealant, leaving the surface slightly below the floor reduces direct wheel contact. Semi-rigid fillers are finished flush with the floor.