Expansion joint sealant fills the gap between building elements while accommodating movement caused by temperature changes, settling and everyday use. Choosing a product suited to the joint’s location and expected movement helps you protect the surrounding materials and maintain a durable seal.
Your choice depends on the substrates, exposure and traffic the joint must handle. You’ll also need to consider joint design, backing material and installation conditions, since each affects the sealant’s performance over time. The backer rod, the tape and the facade and connection sealants named below are in the joint sealing products range; Sikaflex PRO 3 Purform 600ml has its own product page.
How Sealed Expansion Joints Work
An expansion joint needs to accommodate changes in the gap while keeping debris out. Correct joint geometry, suitable sealant and a clean, well-prepared surface help maintain that seal.
Accommodating Movement While Blocking Debris
Concrete and other building materials expand, contract or shift with temperature changes, loading and settlement. A flexible sealant stretches and compresses with the joint, while its bond to both sides keeps the opening sealed.
If the sealant adheres to the bottom as well as the two sides, movement can concentrate stress and lead to tearing. A backer rod helps control sealant depth and prevents three-sided adhesion.
Everbuild Tecnic Joint Backer Rod is sold for reducing the depth of joints and creating a backstop to allow proper sealant tooling; its product page says this improves sealant performance by obtaining the correct joint dimensions. Follow the sealant manufacturer’s instructions for joint dimensions and preparation, including cleaning away dust and loose material.
For demanding floor joints, Sikaflex PRO 3 Purform 600ml has stated movement capability of ±25% under EN ISO 9047, ±35% under EN 14188-2 and ±50% under ASTM C719. Sika lists it for horizontal and vertical interior and exterior joints, including warehouse and production floors, car park decks and tunnels.
For connection joints between porous and non-porous materials, such as windows and doors, Sikaflex AT Connection 600ml has movement capability of ±25% under ISO 9047.
Common Joint Locations and Failure Risks
You’ll find expansion joints in concrete floors, external paving, car parks, tunnels and at connections between building components. Each location brings different demands: vehicle traffic can wear a floor joint, while temperature changes put pressure on external seals.
Choose a product specified for the joint’s location and exposure. Common failures include loss of adhesion, cracking, tearing and sealant sinking too far into a deep joint.
Poor surface preparation, incorrect joint dimensions and sealant that cannot accommodate the movement can all contribute. Debris entering through a failed seal can make movement harder and increase stress on the seal.
For the floor applications in Sika’s data sheet (trafficked areas, car park decks and production floors), Sikaflex PRO 3 Purform 600ml is the sealant this guide follows.
Choosing a Suitable Material
Choose a sealant that matches the joint’s movement, the surfaces it must bond to and the conditions it will face. A suitable backer rod or expansion tape also helps set the joint’s depth and support the sealant.
Movement Capacity, Substrate Compatibility, and Exposure
Check the stated movement capacity against the movement expected in your joint, and compare figures only when the test standard matches the project specification.
Confirm the sealant is intended for your substrates and exposure. Sikaflex PRO 3 Purform 600ml has a service temperature range of -40 °C to +80 °C. Prepare surfaces as the manufacturer directs, and size the joint and backing material to suit the sealant’s specified application.
Installation and Long-Term Performance
A durable joint depends on clean, correctly sized surfaces, a backer rod that controls sealant depth and careful application. Routine checks help you spot adhesion failure, damage or gaps before they affect the joint.
Surface Preparation and Backer Rod Placement
Remove old sealant, dust, laitance, grease and loose material. The joint faces must be clean and sound; follow the sealant manufacturer’s guidance if you need a primer.
Check the joint dimensions and confirm that the selected sealant suits the substrate and expected movement. Fit Everbuild Tecnic Joint Backer Rod to set the sealant depth and prevent three-sided adhesion.
Choose a rod diameter that compresses slightly against the joint sides, then push it into place without stretching or puncturing it. Set it at a consistent depth, using a blunt tool to avoid damage.
Where a backer rod cannot fit, use a bond-breaker tape to stop sealant adhering to the joint base. Correct depth and a clean bond surface help the sealant stretch and recover as the joint moves.
Application, Curing, and Routine Inspection
Apply sealant evenly, keeping the nozzle in contact with the joint faces to reduce air pockets. Tool the bead promptly to press it against both sides and form a neat profile.
For suitable floor and traffic joints, Sikaflex PRO 3 Purform 600ml has a stated application temperature range of 0 °C to +40 °C for both air and substrate. Its skin time is 50 minutes at +23 °C and 50 % relative humidity, with a curing rate of 3.5 mm per 24 hours. Protect fresh sealant from disturbance and water exposure in line with the product instructions.
Inspect joints periodically and after works that could damage them. Look for edge separation, splits, missing sections or persistent gaps; the next section covers what to do when a joint has failed.
Re-sealing a failed expansion joint
An expansion joint sealant has failed when the bead has pulled away from one face, split down the middle, hardened and cracked, or when the joint has widened so far that the bead no longer spans it. Each of these lets water and debris into the joint, so the repair should not wait.
Cut the old sealant out with a sharp blade and scrape the joint faces back to a clean, sound substrate. Remove the old backer rod along with the sealant. Then re-measure the joint width: a joint that has widened needs a larger diameter of Everbuild Tecnic Joint Backer Rod and a sealant whose movement capability covers the movement you now expect.
Re-seal with Sikaflex PRO 3 Purform 600ml following the preparation and application steps above. Check the pack before you start: unopened packs have a shelf life of 15 months from the date of production when stored dry at +5 °C to +25 °C in original, unopened, undamaged packaging.
Not every joint is an expansion joint. Connection joints around window and door frames are the territory of Sikaflex AT Connection 600ml; the Sikaflex AT Connection guide covers that job. Movement and connection joints in concrete and masonry facades take Sikaflex Construction Purform 600ml, which Sika describes as a 1-part, non-sag, elastic polyurethane joint sealant and a low-modulus sealant for concrete and masonry facades; the Sikaflex PRO 3 Purform vs Sikaflex Construction guide compares the two. Joints between a window or door frame and the adjacent wall can also take Sika Expansion Tape 600, a self-adhering, elastic polymer, dispersion impregnated expansion tape sold for joint sealing between window and door frames and adjacent building components. See the joint sealing products at Sealants4All.
