Repair Systems — 01
TPO/FPO sheet membrane systems — exposed roofs and decks
Technical product reference for TPO and FPO heat-weldable sheet membrane systems used on exposed roof decks, balconies, and utility platforms in Australian Class 2 strata apartment buildings. Covers product type classification, installation method selection (fully bonded, loose-laid), substrate compatibility, heat-welding requirements, trafficability, and AS 4654.1 compliance.
What are TPO/FPO sheet membrane systems?
TPO (thermoplastic polyolefin) and FPO (flexible polyolefin) sheet membranes are heat-weldable, plasticiser-free thermoplastic single-ply systems designed for direct UV exposure on roof decks, balconies, and utility platforms. Unlike PVC single-ply membranes that require ballast — pebble, pavers, or growing medium — to protect against UV degradation and plasticiser loss, TPO and FPO membranes are formulated for long-term direct exposure to Australian sunlight, heat, and weathering without any covering above. The plasticiser-free chemistry eliminates the plasticiser migration that limits the service life of PVC-based systems, and produces a membrane that maintains flexibility, weld strength, and UV resistance over time in exposed conditions.
Product Reference
2 products — 1 brand — ARDEX WeldTec TPO range — scroll to view all
System Description
ARDEX WPM 715 is the primary smooth-face TPO sheet membrane in the ARDEX WeldTec range for exposed horizontal and vertical waterproofing applications on Australian roof decks, balconies, and utility platforms. It is installed as a single-layer system — either fully bonded to the substrate using ARDEX WA 98 contact adhesive or loose-laid with heat-welded perimeter upstands and edge restraint. Seams and laps between adjacent sheets are heat-welded using an approved hot-air welding unit with a minimum 40mm overlap. The membrane is UV-resistant and designed to remain exposed without ballast, tile, or growing medium above. On Class 2 strata apartment buildings, WPM 715 is used for roof deck and upper balcony waterproofing remediation where the brief calls for a durable exposed single-ply membrane finish. The smooth face allows either bonded or loose-laid installation depending on substrate condition and moisture content. Critical installation rule: ARDEX WA 98 contact adhesive must not be applied to any area of membrane that will be seam-welded — adhesive-contaminated membrane cannot be heat-welded and the seam will fail. The membrane is available in dove grey or black and complies with AS 4654.1. Roll dimensions are 1.4m wide × 20m long (53 kg per roll). ARDEX WPM 715 is confirmed stocked through ARDEX Australia direct, Bldcare, Waterproofing Direct, and The Waterproofing Shop.
Technical Properties
- TPO (thermoplastic polyolefin) — plasticiser-free — UV-resistant — suitable for long-term direct UV exposure without ballast
- 1.5mm nominal thickness — consistent membrane gauge across the roll
- AS 4654.1 compliant — confirmed on ardexaustralia.com product page
Limitations
- ARDEX WA 98 contact adhesive must NOT be applied over areas that will be heat-welded — adhesive-contaminated seam zones cannot be welded and seam will fail
- Heat welding requires an approved hot-air welding unit — no open-flame or cold bonding at seams — seam integrity is the primary waterproofing security
- Minimum 40mm overlap required at all side and end laps before heat welding — under-welded laps are the most common failure mode
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Description
ARDEX WPM 717 is the fleece-backed variant in the ARDEX WeldTec TPO range. The polyester fleece backing distinguishes it from WPM 715 in two ways: the fleece provides a ventilation layer that allows substrate moisture vapour to escape after installation, and it enables the membrane to be directly bonded to a wider range of substrates through the fleece rather than relying solely on contact adhesive to the smooth membrane face. The fleece-backed format is the preferred choice when substrate moisture content cannot be fully confirmed before installation, as the fleece backing allows any trapped moisture to migrate and disperse rather than blister the membrane face. In Australian Class 2 strata roof deck remediation, WPM 717 is used where the substrate — concrete, plywood, or composite board — may retain elevated moisture or where the fully bonded installation must achieve strong adhesion to an irregular or variable surface. Like WPM 715, seams between adjacent rolls are heat-welded with an approved hot-air welding unit at minimum 40mm overlap. Solvent-wiping of the membrane surface is required before welding all laps. WPM 717 is a fully bonded system only — loose-laid installation is not appropriate with a fleece-backed membrane. The membrane is available in dove grey and is confirmed stocked at 1.4m × 20m roll size through ARDEX Australia direct supply and Bldcare. Confirm current product pricing and availability directly with ARDEX Australia before ordering.
Technical Properties
- TPO (thermoplastic polyolefin) — plasticiser-free — UV-resistant — designed for long-term direct UV exposure
- 1.4mm nominal thickness — fleece-backed — consistent membrane construction
- Fleece backing provides substrate ventilation — allows moisture vapour to escape after installation — reduces blister risk on substrates with elevated moisture
Limitations
- Fully bonded installation only — the fleece backing is not suitable for loose-laid installation — edge restraint and perimeter detailing differ from smooth-face loose-laid system
- Heat welding of all seams and laps is mandatory — approved hot-air welding unit required — no cold bonding at seams
- Minimum 40mm overlap at all side and end laps before welding
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
TPO/FPO sheet membrane system comparison
ARDEX WeldTec range — confirmed Australian products only. Sika Sarnafil AT: confirm Australian availability with Sika Australia before specifying.
| Product | Brand | Material | Thickness | Face | Installation | Loose-laid | Trafficable | AS 4654.1 | Key restriction |
|---|---|---|---|---|---|---|---|---|---|
| WPM 715 | ARDEX | TPO | 1.5mm | Smooth | Fully bonded or loose-laid | Yes | Yes (foot traffic) | Yes — AS 4654.1 | WA 98 must not overlap heat-weld seam zones |
| WPM 717 | ARDEX | TPO | 1.4mm | Fleece-backed | Fully bonded only | No | Yes (foot traffic) | Yes — AS 4654.1 | Bonded only — no loose-laid — dove grey only |
Do not confuse TPO/FPO exposed membranes with:
- Single-ply PVC ballasted membranes (Wolfin IB, Cosmofin, Fatrafol 810v, Sarnafil G 410-L) — PVC with plasticiser, covered by ballast (pebble or pavers), not UV-exposed — separate product category on this site
- Liquid-applied polyurethane and hybrid membranes (ARDEX WPM 157, Sika Sikalastic-487) — applied by roller or brush as a liquid, not a factory-manufactured sheet product
- Torch-on modified bitumen sheet membranes (SBS and APP bitumen) — bituminous chemistry, heat-applied by gas torch, not TPO — different material, different installation, different performance profile
- HDPE sheet membrane systems — high-density polyethylene, different chemistry, typically used below-slab, in planter boxes, or on podium structures with overburden — not UV-exposed
- Cementitious flexible membranes (ARDEX 8+9, Mapei Mapelastic) — two-part cement-based systems applied by brush, not sheet systems
ARDEX WA 98 contact adhesive must not be applied to heat-weld seam zones
ARDEX WA 98 is the solvent-based contact adhesive used to bond WPM 715 to the substrate in fully bonded installations. A critical installation rule applies: WA 98 must not be applied to any area of the membrane or substrate where adjacent sheets will be seam-welded. Contact adhesive contamination prevents the hot-air welding equipment from forming a correct seam — the adhesive residue degrades the weld, and the seam will fail. Plan adhesive application zones carefully before installation to ensure all seam overlap areas (minimum 40mm from the sheet edge on both sheets) remain adhesive-free. Mark seam lines on the substrate before applying WA 98.
All seams and laps must be heat-welded using an approved hot-air welding unit — no cold bonding at seams
ARDEX WeldTec TPO membranes are thermoplastic systems — seams and laps are formed by heat-welding with an approved hot-air welding machine, not by cold bonding with adhesive. Cold-bonded seams are not acceptable and will fail over time. Minimum 40mm overlap is required at all side and end laps before welding. The membrane surface must be solvent-wiped before welding to remove contamination — unwashed membrane surface will not weld correctly and the seam will delaminate. ARDEX requires installation to be carried out by trained and approved applicators using an approved welding unit — confirm accreditation requirements with ARDEX Australia before commencing work.
Sika Sarnafil AT — FPO mechanically fixed membrane — confirm Australian availability
Sika Sarnafil AT is a confirmed FPO (flexible polyolefin) single-ply membrane available internationally in AT-15, AT-18, and AT-25 variants, designed for mechanically fixed exposed roof applications with UV resistance. It is confirmed in Sika UK and Sika global documentation but was not confirmed on the Australian Sika website (aus.sika.com) at the time of publication. If Sarnafil AT is being considered for an Australian Class 2 strata roof project, confirm current Australian product availability, accredited applicator access, and current technical specifications directly with Sika Australia at aus.sika.com or by contacting Sika Australia technical on 1300 22 33 48. Do not specify based on international documentation alone.
Disclaimer
This page provides general technical information only. Final product selection must be confirmed against the current manufacturer technical data sheet, project specification, substrate moisture content, installation method suitability (fully bonded vs loose-laid), AS 4654.1 compliance status, wind uplift requirements, and NCC requirements. Substrate moisture content must be within ARDEX limits before WPM 715 or WPM 717 installation — confirm with ARDEX Australia. WA 98 contact adhesive must not be applied to areas where heat-welded seams will be located. All seams require heat welding with an approved hot-air welding unit — minimum 40mm overlap — solvent-wiped before welding. Maintenance inspection obligations apply to exposed membranes per ARDEX TB272. Do not rely on this reference as a substitute for professional waterproofing consultant advice.