Will it stick over silicone?

No — polyurethane will not adhere to silicone or silicone residue, and nearby uncured neutral silicones can stop it curing. Keep the two chemistries apart.

Do deep joints need a backer rod?

Yes — closed-cell polyethylene backer rod about 25% wider than the joint, so the sealant bonds on two sides only and can flex.

GacoPoly Permathane Polyurethane Sealant

Name: GacoPoly Permathane Polyurethane Sealant
Brand: Gaco
Price: 6.72 GBP
Availability: InStock

Key Features

Compatibility warning — silicone and this sealant do not mix. Permathane SM7120 PU is a polyurethane. The manufacturer states: “When applied in close proximity, neutral cure silicones will prevent SM7120 PU from curing… SM7120 PU will not adhere to silicone or its residue.” Do not use it for detail work on a Gaco silicone roof system (GacoFlex S42 / SF4200) — the silicone-compatible detail product there is SF4200 SeamSeal. Where compatibility with asphalt flashings is required, use SM7713 MS instead. Advice: 01208 832 602.

Coverage — no figure is published, and that is deliberate

The current technical data sheet for SM7120 PU carries no coverage, yield or linear-rate section at all. On a gun-grade joint sealant the yield is a function of the joint the specifier designs, not a property of the material, so the manufacturer publishes the joint rules instead of a number. We will not invent one.

Sealant depth must not exceed the joint width.
Depth must be no greater than 12.7 mm (½ in) and no less than 6.4 mm (¼ in).
In deep joints, use closed-cell polyethylene backer rod approximately 25% larger than the joint width to set the depth; in shallow joints use a bond-breaker film to prevent three-sided adhesion.
Do not puncture or prime the backer rod.

Work the requirement out from the joint geometry and the run length. If you would like us to do that with you, call 01208 832 602.

Pack sizes: 10.1 fl oz cartridge (299 ml) and 20 fl oz sausage (591 ml). There is no pail size for this product.

GacoPoly Permathane Polyurethane Sealant

GacoPoly Permathane is a professional, one-component polyurethane sealant that guns smoothly, tools cleanly, and cures to a durable, permanently flexible joint.

Moisture-curing, non-sag — gun-grade polyurethane sealant for vertical and overhead joints; holds profile without slumping.
Permanently flexible — accommodates typical building movement (expansion/contraction, vibration) without cracking or splitting.
Primerless adhesion — bonds to concrete, masonry, galvanized/painted metal, aluminium, timber, PVC/FRP, glass and many coated surfaces.
Weather & UV durable — exterior-rated polyurethane sealant that resists rain, sunlight, freeze–thaw and thermal cycling.
High tear & peel strength — robust bead stands up to traffic, cleaning and seasonal movement at façades and floor perimeters.
Paintable after cure — compatible with most water-borne and many solvent-borne paints (test first on critical finishes).
Low-VOC compliance — professional results with job-site friendly odour; suitable for occupied facilities with normal ventilation.
Versatile use cases — expansion/control joints, window/door perimeters, metal building seams, flashings, gutters, penetrations, and floor-to-wall joints before coating.
Colour & pack — contractor-standard 10.1-oz cartridge in popular colours for neat, repeatable detailing.
System friendly — ideal companion to Duratite/Gaco floor systems: seal cracks and edges with this polyurethane sealant before priming and coating.

Typical Applications

GacoPoly Permathane Polyurethane Sealant

GacoPoly Permathane is a one-component polyurethane sealant for flexible, weatherproof joints on concrete, masonry, metals, timber and many plastics—ideal wherever movement, watertightness and clean detailing matter.

Concrete slab joints — expansion/control joints in warehouses, factories and loading docks; size with backer rod for correct geometry.
Perimeter caulking — window/door frames, storefronts and curtain wall mullions for airtight, watertight seals.
Precast & tilt-up panels — vertical panel joints and masonry control joints exposed to weather and thermal cycling.
Metal building seams — panel laps, standing-seam terminations, trims and ridge/corner details; adheres to coated/galvanized metals.
Floor-to-wall transitions — base angles and perimeters before coating; helps prevent moisture tracking under floor systems.
Service penetrations — HVAC, plumbing, electrical sleeves and conduits through walls/slabs.
Cold joints & saw cuts — non-structural crack routing and sealing prior to priming/coating.
Balconies, stairs & landings — perimeter beads, nosings and flashing interfaces subject to rain and wash-downs.
Parapets & flashings — coping joints, counter-flashings, gutters and downpipe terminations.
Metal-to-concrete interfaces — thresholds, bollard bases, plates and fixings where dissimilar materials move differently.

Use correct joint design (width/depth, backer rod), prime only where required by substrate, and avoid permanent immersion or movement beyond the product’s stated capability.

GacoPoly Permathane Polyurethane Sealant

GacoPoly Permathane is a one-component, moisture-curing polyurethane sealant for professional joints and perimeter seals. Correct joint design, clean substrates and the right tools are what make the bead last.

Equipment checklist

Dispensing: professional caulk gun (smooth-rod or pneumatic), spare nozzles, puncture tool
Joint design: closed-cell backer rod (various diameters) or bond-breaker tape for shallow joints
Masking & tooling: painter’s tape, steel/plastic tooling spatula, approved tooling agent (non-soapy), rags
Surface prep: knife/scraper, wire brush or light abrasive, solvent wipes as appropriate, HEPA vac
Priming (if required): substrate-specific primer per manufacturer guidance
PPE: nitrile gloves, eye protection, suitable respirator where ventilation is limited

Application

Design the joint
- Target a 2:1 width:depth rule of thumb (narrow joints: 1:1).
- Install backer rod to control depth and prevent 3-sided adhesion; use bond-breaker tape where rod won’t fit.
- Allow for expected movement (Permathane accommodates typical building movement; see project spec).
Prepare the substrate
- Remove dust, laitance, old caulk, oils and loose coatings. Edges must be clean, dry and sound.
- Lightly abrade non-porous surfaces if needed; solvent-wipe and let flash dry.
- Prime only if required for difficult substrates—test adhesion first.
Mask
- Tape both sides of the joint for crisp lines and to control squeeze-out.
Gun the bead
- Cut nozzle to joint width (slight “V” helps wet edges). Puncture inner seal and load the cartridge.
- Apply continuous pressure, pushing the bead forward to wet the flanks. Avoid gaps and entrained air.
Tool immediately
- Tool once, firmly, to a slightly concave profile that presses sealant into both sides.
- Use a clean spatula; if using a tooling agent, choose one approved for polyurethane sealant (avoid soapy water that can cause surface issues).
- Pull masking tape right away for sharp edges.
Cure & protection
- Protect from rain, dust and contact until skinned; allow full cure before painting or exposing to heavy movement/cleaning (time is ambient-dependent: thicker beads and low humidity cure slower).
Painting (optional)
- Paint after full cure with compatible coatings; test adhesion/compatibility first, especially on high-build or rigid paints.
Cleanup & maintenance
- Uncured: wipe with suitable solvent compatible with polyurethane sealant; dispose of rags safely.
- Cured: trim or remove mechanically; over-seal after proper prep if repairs are needed.
- Inspect joints periodically; repair local damage by cut-out, clean, prime (if required) and re-seal.

Quick spec notes

Use correct joint geometry (backer rod sized approximately 25% larger than joint gap).
Do not bridge movement joints with rigid fillers behind the bead.
Install only within ambient limits (dry substrates, above dew point, good ventilation).
For floor-to-wall or traffic-adjacent joints, select joint dimensions and backer rod density appropriate to expected movement and cleaning regime.

Following this workflow delivers neat, durable, watertight joints and the long-term flexibility you expect from a pro-grade polyurethane sealant.

Technical Performance

GacoPoly Permathane Polyurethane Sealant

GacoPoly Permathane is a one-component, moisture-curing polyurethane sealant that forms a durable, elastomeric joint for demanding façade and flooring interfaces. It’s engineered for long-term flexibility, weatherability and adhesion on common construction substrates.

Movement capability — Accommodates ±35% joint movement when correctly designed (backer rod/bond-breaker, width–depth control).
Elastomeric durability — Medium-modulus, high-elongation film resists cracking, splitting and compression set under cyclical thermal/vibration loads.
Non-sag profile — Guns cleanly and holds shape in vertical/overhead joints; tools to a smooth, slightly concave weather bead.
Adhesion envelope — Primerless bond to most concrete, masonry, galvanized/painted metals, aluminium, timber, PVC/FRP, and glass; primer may be required on dense, glazed or contaminated surfaces—test first.
Weather & UV resistance — Exterior-rated bead resists rain, sunlight, freeze–thaw and de-icer exposure; maintains flexibility across seasonal temperature swings.
Chemical & cleaning resistance — Withstands water, dilute acids/alkalis, salt spray and routine detergents. Not intended for strong solvents, harsh chemicals or permanent immersion.
Cure profile — Skins in hours; cures through from the surface inward. Final cure time varies with bead size, temperature and humidity (thicker beads and dry/cool air cure slower).
Paintability — Paintable after full cure; verify compatibility (use flexible coatings; adhesion test recommended on critical finishes).
Floor-edge performance — Tough tear/peel resistance for floor-to-wall joints and perimeter beads ahead of coating; supports cleaning regimes without shedding.
Service environment — Remains flexible in typical building-envelope temperatures; install only on dry substrates above dew point with adequate ventilation.
Compatibility in systems — Integrates with Duratite/Gaco flooring assemblies: seal cracks, saw cuts and perimeters before priming/coating to prevent moisture tracking.
Packaging — Contractor-standard 10.1-oz cartridge with colour options suited to façade and floor detailing.

Use correct joint design (backer rod, bond-breaker, width/depth ratio), clean substrates thoroughly, and follow site QA (mock-ups, adhesion tests) to achieve the stated performance from this polyurethane sealant.

Surface Preparation

GacoPoly Permathane Polyurethane Sealant

Goal: clean, dry, sound joint faces with correct geometry so the polyurethane sealant bonds and moves as designed.

1) Joint design (before any prep)

Width : depth ≈ 2:1 (narrow joints may use 1:1).
Depth limits (typ.): 6–13 mm (¼–½”)—avoid over-deep beads.
Backer rod: closed-cell, approximately 25% larger than joint gap. Use bond-breaker tape where rod won’t fit.
Movement joints: design for expected ± movement; don’t allow 3-sided adhesion.

2) Remove existing materials

Cut out old sealant and soft/loose fillers completely.
Scrape, wire-brush, vacuum. For stubborn residues, abrade lightly and solvent-wipe (approved solvent), then allow to flash dry.

3) Substrate preparation (by type)

Concrete / Masonry: Grind or abrade to sound, laitance-free edges; remove curing agents, dust, oil, paint. Vacuum (HEPA) clean and dry. Route non-structural cracks to a neat, uniform slot before rod & seal.
Metals (galv., aluminium, coated steel): Remove oxidation and contaminants; light abrade glossy finishes; solvent-wipe with lint-free cloth; dry fully.
Timber: Sound, dry wood only. Sand to fresh surface, remove dust.
Plastics & FRP/PVC: Clean with compatible cleaner; lightly abrade glossy faces; test a small area for solvent sensitivity and adhesion.
Glass / Glazed surfaces: Degrease, wipe with IPA; ensure smear-free, dry edges.

4) Priming (only if required)

Many substrates bond primerless; difficult, dense or contaminated ones may need a compatible primer. Always adhesion-test first and follow primer recoat windows.

5) Masking & final readiness

Mask joint margins for crisp edges.
Install backer rod at uniform depth; ensure faces are clean, dry, dust-free, and substrate is ≥ 3 °C above dew point.
Avoid rain, wash-down and condensation during installation and early cure; provide ventilation.

6) Quick checklist (go/no-go)

Correct joint width/depth and backer rod in place
All old sealant removed, edges sound
Surfaces clean, dry, solvent fully flashed
Primer used only where specified and within window
Ambient conditions within project limits and stable

Proper preparation is the single biggest factor in long-term performance—get the joint geometry right, clean the faces thoroughly, and your polyurethane sealant will do the rest.

Primers & Topcoats

GacoPoly Permathane Polyurethane Sealant

Role in the system: GacoPoly Permathane is a one-component polyurethane sealant that normally bonds primerless to many construction substrates. Use a primer only where the surface is difficult or where an adhesion test indicates it’s needed. It is not a “topcoat” itself, but it can be painted after full cure with compatible coatings.

When a primer may be required

Dense / low-energy surfaces: anodized aluminium, fluoropolymer finishes (e.g., Kynar®), powder-coated metals, glazed masonry/ceramics.
Metals prone to oxidation: galvanised steel, bare aluminium—after proper cleaning/abrading.
Chalky or porous substrates: weathered concrete/masonry that remains dusty after prep.
Cold, damp or marginal conditions: when site constraints limit ideal surface prep.
Critical or high-movement joints: curtain wall perimeters, submerged splash zones, or where failure is high-risk.
If the field adhesion test fails: always revert to a compatible primer and retest.

Primer best practice: Clean and dry the joint faces, abrade glossy areas, solvent-wipe and allow to flash. Apply the substrate-specific sealant primer in a thin, even film; respect its recoat window. Always perform a site adhesion test before proceeding at scale.

Painting / “topcoating”

Paint only after full cure. Cure time depends on bead size, temperature and humidity.
Use flexible coatings (high-quality acrylics/urethanes). Rigid films can crack over a moving joint.
Adhesion-test the chosen paint on a cured bead first, especially over metals and factory finishes.
Do not flood the bead with heavy build paint—maintain the sealant’s movement capability and profile.
Avoid strong-solvent coatings that may soften fresh polyurethane sealant; if used, extend cure time and test first.

In flooring systems (edges & transitions)

For floor-to-wall/perimeter detailing before coatings: install backer rod, gun and tool a slightly concave bead; let it cure fully.
Do not bridge live movement joints with rigid floor coatings. If traffic marking or sealers are applied nearby, keep them thin at the bead edge and avoid glazing the sealant surface.

Line marking & logos

Apply only after sealant has fully cured. Use compatible paints/inks and perform a small adhesion test; avoid pooling material on the bead.

What not to do

Don’t rely on primer to fix poor prep—clean, dry, sound surfaces are mandatory.
Don’t paint or coat uncured sealant.
Don’t apply over wet, frosted or contaminated joints, or where three-sided adhesion exists (use backer rod/bond-breaker).
Don’t use in permanent immersion unless specifically qualified for it.

QA & sign-off

Produce a small mock-up: install bead with the intended prep/primer/paint sequence, let cure, then perform a simple peel test (scribe and pull).
Record substrates, primers (if any), cure times and paint types used. This locks in a repeatable method for the rest of the project.

Handled this way, your polyurethane sealant joints achieve reliable adhesion, clean edges, and long-term flexibility—whether left exposed or painted to match surrounding finishes.

Compliance & Certification

GacoPoly Permathane Polyurethane Sealant

GacoPoly Permathane is a professional polyurethane sealant supplied with the documentation specifiers need for regulated jobs. The notes below summarise its standard conformance, usage limits and QA expectations—clean and link-free for your product page.

Primary standard — Conforms to ASTM C920 for elastomeric joint sealants: Type S (one-component), Grade NS (non-sag), Class 35 (±35% movement), Use NT, M, A, G, O (non-traffic; masonry; aluminum; glass; other substrates as tested).
Intended service — Exterior/interior weather-sealing and perimeter joints; vertical/overhead beads. Not intended for continuous immersion or for horizontal traffic joints (specify a self-levelling grade for traffic).
VOC & emissions — Low-VOC, jobsite-friendly odour; formulated to meet typical U.S. and regional VOC limits for architectural sealants (including strict jurisdictions) when installed with normal ventilation controls.
Paintability & finishes — Paintable after full cure with many water-borne and select solvent-borne coatings; verify by on-site adhesion/compatibility test, especially over factory finishes (e.g., fluoropolymers).
Substrate compatibility — Bonds (often primerless) to common construction materials (concrete/masonry, coated or galvanised metals, aluminium, timber, PVC/FRP, glass). Use substrate-specific primer only if field adhesion tests indicate.
Temperature & weathering — Designed for façade temperature swings, UV exposure and freeze–thaw; maintains elasticity within the published service temperature range when properly joint-designed.
Health & safety documentation — Supplied with GHS/CLP-compliant labels plus current SDS and PDS for contractor RAMS/COSHH files (mixing/handling, PPE, storage, disposal).
Quality assurance — Batch numbers on cartridges for traceability. Recommended on-site QA: joint design checks (width/depth, backer rod), surface-prep sign-off, and field adhesion tests (scribe-and-peel) before full production.
Regulatory & warranty notes — Compliance and warranty require correct joint design (backer rod/bond-breaker), clean/dry substrates, installation within ambient limits, and adherence to recoat/paint guidance. Do not bridge structural movement joints with rigid coatings.

This section positions Permathane clearly: a Class 35, non-sag polyurethane sealant for professional weather-sealing, with low-VOC compliance and the documentation needed for specification, submittals and site QA.

Health & Safety

GacoPoly Permathane Polyurethane Sealant

GacoPoly Permathane is a one-component, moisture-curing polyurethane sealant. Like all PU sealants, it can irritate skin/eyes and may cause respiratory sensitisation. Read and brief crews to the current SDS/PDS before use, and set up the job with ventilation, PPE and clean handling.

Key hazards

Sensitiser (isocyanate-bearing PU): Repeated exposure can cause skin/respiratory sensitisation. Avoid skin contact and inhalation of vapours/aerosols.
Vapours/aerosols: Low-VOC does not mean risk-free. Gunning, tooling and any spray can create aerosols—control with ventilation and RPE as needed.
Eye/skin irritation: Fresh sealant and cleaners can irritate; remove promptly from skin (no solvents on skin).
Slip/contamination risk: Fresh beads are tacky and can transfer—protect adjacent finishes.
Prep hazards: Grinding/saw-cutting joints generates dust and noise—use extraction and hearing protection.
Environmental harm: Prevent uncured product or solvent wipes entering drains/watercourses.

PPE (minimum)

Respiratory: Half-mask with organic vapour + P2/P3 particulate filters when ventilation is inadequate or aerosols may form.
Hands: Nitrile or equivalent chemical-resistant gloves; change regularly.
Eyes/face: Chemical splash goggles; face shield when decanting/cleaning.
Clothing/feet: Protective garments and impervious safety footwear.
Hearing: Protection during mechanical prep.

Ventilation & site controls

Provide cross-flow or mechanical extraction in enclosed areas.
Keep substrates clean, dry and above dew point; avoid application in rain/condensation.
Set up exclusion/cleanup zones to keep fresh beads off finished surfaces.

Safe handling & application

Stage cartridges, backer rod and masking so joints are sealed in one pass; maintain a steady bead to avoid voids.
Use backer rod or bond-breaker tape to prevent three-sided adhesion and overstress.
Tool immediately to a smooth, slightly concave profile; pull tape at once for clean edges.
Do not thin. Do not apply over wet, frozen or contaminated joint faces.
Allow full cure before painting or exposing to heavy movement/cleaning.

Storage & transport

Store upright, sealed, cool and dry, away from heat/oxidisers.
Protect from freezing and direct sun. Observe shelf life; rotate stock FIFO.

First aid (summary)

Inhalation: Move to fresh air; rest; seek medical advice if symptoms persist.
Skin: Remove contaminated clothing; wash with soap and water (no solvents).
Eyes: Rinse with water for ≥15 min; remove lenses if easy; get medical attention.
Ingestion: Rinse mouth; do not induce vomiting; seek urgent medical care.

Spills & waste

Scrape up bulk; absorb residues with inert material. Collect in labelled containers.
Prevent entry to drains/watercourses.
Dispose of uncured waste, absorbents, used PPE and empty cartridges as hazardous waste per local regulations.

Fire

Cured residues and contaminated rags can burn. Suitable extinguishers: foam, dry chemical, CO₂. Fire-fighters should use SCBA.

After installation

Protect beads until skinned and cured.
Clean with neutral detergents; avoid strong solvents on or near the bead.
Inspect joints periodically; for repairs, cut out defective sections, clean, prime if required, and re-seal.

This summary supports, but does not replace, the project RAMS/COSHH and the latest SDS/PDS. Follow those documents for definitive requirements when working with this polyurethane sealant.

Important Notes

GacoPoly Permathane Polyurethane Sealant

The points below are the critical do’s-and-don’ts for installing GacoPoly Permathane. Follow them to achieve clean edges, reliable adhesion and long-term flexibility from this professional polyurethane sealant.

System intent — Weather-sealing and perimeter joints on façades and floors; not a structural adhesive, not for permanent immersion, and not for horizontal traffic joints (use a self-levelling grade for traffic).
Movement capability — Design joints for ±35% movement. Use correct geometry (typically 2:1 width:depth, narrow joints up to 1:1), and prevent three-sided adhesion with backer rod or bond-breaker tape.
Backer rod sizing — Closed-cell rod approximately 25% larger than joint gap; rod sets depth, saves material and preserves movement.
Substrate condition — Joint faces must be clean, dry, sound: remove old sealant, dust, laitance, oils, curing agents and loose coatings; lightly abrade glossy, coated or oxidised metals and solvent-wipe before sealing.
Primer use — Often primerless; prime only where adhesion testing indicates. Always perform a simple field adhesion (scribe-and-peel) test on each substrate/finish.
Ambient limits — Apply on dry substrates above dew point; avoid rain, condensation and washing during skin/cure. Provide ventilation in enclosed areas.
Painting — Paint only after full cure with flexible coatings. Always adhesion-test paint on a cured bead; rigid films can crack over moving joints.
Compatibility cautions — Check for plasticiser migration from adjacent materials (PVCs, some rubbers). Separate bituminous or tar materials that can bleed into the bead.
Floor edges & coatings — For floor-to-wall transitions, set backer rod and seal before priming/coating adjacent floors; allow full cure, then keep coatings thin at the bead edge (don’t glaze the sealant).
Bead finishing — Tool immediately to a slight concave profile; pull masking right away for crisp lines. Avoid soapy water as a tooling agent unless confirmed compatible with polyurethane.
Repairs & maintenance — For local failures, cut out to sound edges, clean, prime if required, and re-seal. Inspect joints periodically in high-movement or high-UV areas.
Storage & shelf life — Store cartridges upright, cool, dry, away from heat/oxidisers and direct sun; rotate stock FIFO and observe expiry.
Safety — PU sealants may contain isocyanate chemistry; ventilate, wear suitable PPE (gloves, eye protection, RPE if needed) and prevent uncured product or solvent wipes entering drains.

Type	One-component, non-sag, moisture-cure polyurethane sealant
Movement	±35% joint movement (ASTM C920 Type S, Grade NS, Class 35)
Elongation	685% at break; hardness Shore A 40 (ASTM D412 / D2240)
Cure	Skins in 2–4 h; full cure 2–7 days (6 mm bead at 24 °C / 50% RH)
Service range	−40 °C to +85 °C
Adhesion	Primer-less on galvanised steel, aluminium, concrete, glass, Kynar, timber, vinyl and fibreglass
Approvals	US Fed Spec TT-S-00230C Class A; AAMA 808.3; USDA acceptable

GacoPoly Permathane Polyurethane Sealant

Where Permathane goes

Construction & expansion joints

Window & door perimeters

Metal buildings & cladding

Why contractors choose Permathane

±35% movement

Primer-less on most substrates

−40 °C to +85 °C

Federal & AAMA approved

Specification

Product detail

GacoPoly Permathane Polyurethane Sealant

GacoPoly Permathane Polyurethane Sealant

Equipment checklist

Application

Quick spec notes

GacoPoly Permathane Polyurethane Sealant

GacoPoly Permathane Polyurethane Sealant

1) Joint design (before any prep)

2) Remove existing materials

3) Substrate preparation (by type)

4) Priming (only if required)

5) Masking & final readiness

6) Quick checklist (go/no-go)

GacoPoly Permathane Polyurethane Sealant

When a primer may be required

Painting / “topcoating”

In flooring systems (edges & transitions)

Line marking & logos

What not to do

QA & sign-off

GacoPoly Permathane Polyurethane Sealant

GacoPoly Permathane Polyurethane Sealant

Key hazards

PPE (minimum)

Ventilation & site controls

Safe handling & application

Storage & transport

First aid (summary)

Spills & waste

Fire

After installation

GacoPoly Permathane Polyurethane Sealant

Permathane is part of a system

Downloads

Common questions

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