What is Selleys Pro Trade Joint Sealant LM, and where should you use it?
Pro Trade Joint Sealant LM is a non-slumping polyurethane joint sealant with high movement capability, low modulus and excellent adhesive properties. It is weatherproof, suitable for indoor and outdoor applications, and paintable after it has cured. In use it is a multipurpose, one component high performance polyurethane sealant and elastic adhesive, designed for sealing expansion and construction joints in vertical and horizontal applications.
The "LM" is the point of the product: low modulus. A low-modulus sealant puts less stress back into the joint faces as it stretches, which matters on precast panels, tilt-up construction and masonry, where a stiff sealant can pull the surface off the substrate rather than moving with the joint. It is certified according to EN 15651 — sealants for non-structural use in joints in buildings and pedestrian walkways.
Technical specification
| Property | Typical result |
|---|---|
| Technology | Polyurethane |
| Colour | White, grey and black |
| Density | 1.2 ±0.03 g/ml |
| Application temperature | 5°C to 40°C |
| Tack-free time (23°C, 50% R.H.) | 20–70 minutes |
| Cure rate (23°C, 50% R.H.) | 2.5mm per 24 hours |
| Sagging (EN ISO 7390) | 0mm |
| Tensile strength (ASTM D412) | 1.5–2.0 N/mm² |
| Elongation at break (ASTM D412) | 600% |
| Shore A hardness (ASTM C661) | Approx. 35–40 |
| Modulus at 100% elongation (ISO 8339) | 0.35–0.40 N/mm² |
| Movement capability (EN 15651) | ±25% |
| Service temperature | −40°C to +90°C |
| Packaging | 600ml foil sausage and 310ml cartridge, each in white, grey and black |
These are indicative data only, not intended for the preparation of specifications.
What the key numbers mean in practice
600% elongation at break with a modulus at 100% elongation of 0.35–0.40 N/mm² is the combination that defines a low-modulus sealant. Elongation says how far it stretches before it tears; modulus says how hard it pulls back while stretching. Low modulus is what protects a weak or aged substrate — the joint moves, the sealant follows, and the bond line is not loaded past what render, brick or precast concrete can take.
Sagging of 0mm to EN ISO 7390 means it holds its shape in vertical and overhead joints. On a tilt-up panel joint several metres tall, a sealant that slumps leaves the top of the run starved and the bottom bulging before it cures.
Cure rate is 2.5mm per 24 hours. The sealant cures inward from the surface, so joint depth sets the schedule: a joint at the minimum 10mm depth takes roughly four days to cure through. Do not judge readiness by the tack-free surface.
Tack-free at 20–70 minutes is a wide range because conditions vary. Treat 20 minutes as your planning figure in warm, humid weather. All tooling must be finished before the surface goes tack-free, so work in lengths you can complete.
Service temperature of −40°C to +90°C is a wider range than the FC version of this product, which is worth knowing for joints on dark cladding or roofing that get very hot in summer. Note that it is separate from the application temperature of 5°C to 40°C — the range you should be working in.
Joint design — get this right first
- The optimum width to depth ratio for joint sealing is 2:1.
- Minimum joint width and depth is 10mm.
- For joint widths up to 12mm, use a width to depth ratio of 1:1.
- For joint widths greater than 12mm, use a width to depth ratio of 2:1.
The manufacturer adds three notes. Wider joints can accommodate more total movement than narrow joints — ±25% of 30mm is a much larger absolute movement than ±25% of 10mm, which is worth remembering at design stage. Always install a suitable diameter backing rod (polyethylene or polyurethane foam rod) to control sealant depth and ensure free movement. And the sealant must adhere to the sides of the joints only and NOT to the back, so that it is free to stretch — three-surface adhesion is the most common reason a correctly specified sealant still fails.
Coverage
| Joint width | Joint depth | Joint length per 600ml |
|---|---|---|
| 15mm | 8mm | 5 m |
| 20mm | 10mm | 3 m |
| 25mm | 12mm | 2 m |
| 30mm | 15mm | 1.3 m |
| 35mm | 15mm | 1.1 m |
Where to use it
For sealing and bonding common building materials, including:
- Precast and tilt-up panels, external wall and cladding joints
- Weatherproofing joints between brickwork, masonry, concrete, cladding, wood or metal frames
- External joints in walls and around window or door frames
- Joints in bridge and balcony parapets
- Retaining walls
- Roofing
- Acoustic rated walls
- As an adhesive for indoor and outdoor bonding of window sills, thresholds, stair steps, skirting boards, base boards, crash protection boards, covering boards and prefabricated elements
It has excellent adhesion on common building materials such as concrete, masonry, brick, ceramic tile, metals, soft wood, hardwood and some plastics. It cures bubble free, has no shrinkage during curing, and offers excellent resistance to ageing and weathering. Selleys also states that it will not degrade acoustic walls that meet the BCA requirements. For a fast-curing polyurethane in the same range, see Pro Trade Joint Sealant FC, or browse the construction sealant range.
How to apply it
Surfaces must be clean, dry and free from oil, grease, release agents, dust and loose material. Install a backing rod to the correct depth and apply masking tape as required. The product generally has good adhesion properties without priming to the common building materials indicated, but a pre-test to ensure suitable adhesion is recommended.
The directions below should only be used as a guide — the installer should apply all Australian Standards, BCA/NZBC requirements, and best practices when installing.
As a sealant
- Cut the end of the sausage and insert it into a Selleys sausage gun. For cartridges, completely pierce the metal foil seal inside the cartridge nipple, trim the nozzle and screw it onto the cartridge, then insert into a caulking gun.
- Extrude the sealant into the joint so that it is in full contact with the sides of the joint. Avoid overlapping the sealant, which traps air in the bead.
- Smooth the sealant with a spatula, forcing it into the joint for better contact with the sides.
- Paint with water-based paints after curing. If solvent-based paints are used, prime first with a water-based primer.
As an adhesive
- Ensure surfaces are clean, dry and free from oil, grease, release agents, dust and loose material.
- Apply the sealant in spots or beads on the prepared surfaces.
- Firmly press the parts together.
- If necessary, use a suitable fixing until the adhesive has cured. With a cure rate of 2.5mm per day, a bonded joint needs support for longer than most people expect.
Limitations — where it should NOT be used
- Not recommended for continuous submersion or below water-line use.
- Will not adhere to polyethylene or polypropylene. Test adhesion on other plastics before application.
- Do not apply on frozen or wet surfaces, or through standing water.
- Paint restrictions: suitable for most water-based paints. For oil-based paints, undercoat with a water-based primer. Testing is recommended if paint is applied more than 5 days after sealant application.
The five-day painting note is the one that most often derails a programme. A polyurethane surface keeps changing as it cures, so paint adhesion at day two is not evidence of paint adhesion at day twelve. If the painting trade follows well behind the sealing trade, test on a bead of the same age before committing to the whole facade.
Clean up and storage
Tools and uncured product may be cleaned using mineral turps. Cured product can only be removed mechanically.
Shelf life is 15 months if stored in its original package, away from direct sunlight and moisture, between 10°C and 25°C.
Hazard classification
Selleys Pro Trade Joint Sealant LM is not classified as hazardous under the criteria of Safe Work Australia GHS 7. No signal word is assigned, no hazard statements apply, and the poison schedule is not applicable.
It is not classified as Dangerous Goods for any transport mode — not under the Australian Code for the Transport of Dangerous Goods by Road & Rail or New Zealand NZS5433 on land, not under the IMDG Code by sea, and not under the IATA Dangerous Goods Regulations by air.
That is worth stating plainly for a polyurethane sealant, because polyurethane is the family where a sensitisation classification most often appears — free isocyanate monomer is the usual cause. This product carries none. The safety data sheet does not detail the composition in the material available here, so that is an observation about the classification rather than a claim about the formulation.
Two ordinary precautions still apply and are worth the seconds they cost. Natural ventilation is adequate under normal use conditions, but the safety data sheet's own advice is to avoid inhaling dust and to maintain adequate air circulation in the work area — which is about the enclosed expansion joint in a basement or riser, not the open balcony. And keep it out of your eyes: if it gets in, wash out immediately with water and seek medical advice as a precaution. Wash your hands before eating, drinking or smoking, and store it upright in a cool, dry, well-ventilated place away from direct sunlight, heat and ignition sources.
Common questions about Pro Trade Joint Sealant LM
What does "LM" mean, and why does it matter?
Low modulus. The sealant stretches under less stress, so it puts less load back into the joint faces — which suits precast, masonry and other substrates where a stiffer sealant could pull the surface away.
How much movement will it take?
±25% movement capability, tested to EN 15651.
What standard is it certified to?
EN 15651 — sealants for non-structural use in joints in buildings and pedestrian walkways.
How long before it is tack-free?
20 to 70 minutes at 23°C and 50% relative humidity. Finish tooling before that.
How fast does it cure through?
2.5mm per 24 hours, so a 10mm joint takes about four days to cure through.
Can I paint it?
Yes, after curing, with most water-based paints. For oil-based paints, undercoat with a water-based primer. Testing is recommended if you paint more than 5 days after application.
Do I need to prime the substrate?
It generally has good adhesion without priming to the common building materials listed, but a pre-test is recommended.
Do I need a backing rod?
Yes — always install a suitable diameter polyethylene or polyurethane foam backing rod. The sealant must bond to the sides of the joint only, not the back.
What joint dimensions should I use?
Minimum 10mm width and depth. Up to 12mm wide use a 1:1 width to depth ratio; above 12mm use 2:1.
Will it sag in a vertical joint?
No — sagging is 0mm to EN ISO 7390, and it cures bubble free with no shrinkage.
Will it stick to plastic?
Not to polyethylene or polypropylene. Test other plastics before application.
Can I apply it in wet weather?
No. Do not apply on frozen or wet surfaces, or through standing water.
Can it be submerged?
No — not recommended for continuous submersion or below water-line use.
Will it affect an acoustic rated wall?
Selleys states it will not degrade acoustic walls that meet the BCA requirements.
What sizes and colours are available?
600ml foil sausages and 310ml cartridges, in white, grey and black.
How long does it keep?
15 months in its original package, out of direct sunlight and moisture, stored between 10°C and 25°C.
What is Pro Trade Joint Sealant LM?
Pro Trade Joint Sealant LM is a non-slumping polyurethane joint sealant made by Selleys, offering high movement capability, low modulus, and excellent adhesive properties for demanding joint sealing and bonding applications.
What colours is Pro Trade Joint Sealant LM available in?
Pro Trade Joint Sealant LM is available in White, Grey, and Black.
What is the movement capability and modulus of Pro Trade Joint Sealant LM?
Pro Trade Joint Sealant LM offers high flexibility with ±25% joint movement capability and is a low modulus sealant, allowing it to accommodate thermal expansion and contraction in construction joints.
What is the sag rating of Pro Trade Joint Sealant LM?
Pro Trade Joint Sealant LM has a sag rating of 0mm, tested according to EN ISO 7390, confirming its non-slumping formulation.
What are the tack-free time and cure rate for Pro Trade Joint Sealant LM?
Pro Trade Joint Sealant LM has a tack-free time of 20–70 minutes at 23°C/50% relative humidity, and a cure rate of ≥2.5mm per 24 hours.
What is the service temperature range of Pro Trade Joint Sealant LM?
Pro Trade Joint Sealant LM has a service temperature range of –40°C to +90°C.
What are the tensile strength, elongation at break, and Shore A hardness of Pro Trade Joint Sealant LM?
Pro Trade Joint Sealant LM has a tensile strength of approximately 1.5–2.0 N/mm², an elongation at break of ≥600%, and a Shore A hardness of approximately 35–40.
What are the limitations of Pro Trade Joint Sealant LM?
Pro Trade Joint Sealant LM is not suitable for continuous submersion or below-water-line use, won't adhere to polyethylene or polypropylene without testing, should not be applied on frozen or wet surfaces, and requires priming for oil-based paints, especially if painting occurs more than 5 days after application.
What is the recommended application temperature for Pro Trade Joint Sealant LM?
Pro Trade Joint Sealant LM should be applied at temperatures between 5°C and 40°C.
How should Pro Trade Joint Sealant LM be applied?
According to the directions for use, surfaces should first be cleaned and dried, removing oil, grease, and dust; a backing rod should be inserted if required and edges masked for a neat finish; the nozzle is cut and the cartridge or sausage loaded into a gun; sealant is extruded evenly into the joint ensuring full side contact while avoiding air entrapment; the joint is then tooled off for a smooth finish; once cured, it can be painted with water-based paints (oil-based paints require priming first); uncured sealant is cleaned with mineral turps, while cured sealant must be removed mechanically.
In what packaging formats is Pro Trade Joint Sealant LM available?
Pro Trade Joint Sealant LM is available as a 600 mL foil sausage and a 310 mL cartridge, both offered in white, grey, and black.
What surfaces does Pro Trade Joint Sealant LM adhere well to?
Pro Trade Joint Sealant LM demonstrates excellent adhesion to common building materials including concrete, masonry, brick, ceramic tile, metals, soft wood, hardwood, and some plastics.