C578 Type X SHIPLAP
Grade
SHIPLAP = shiplap / tongue-and-groove edge board
Use where board-to-board joints must block air and thermal bridging without taping.
Values for the SHIPLAP condition
Other C578 Type X grades and fills
C578 Type X is listed in 4 conditions; see the grade overview at C578 Type X.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Grooved / channelled drainage board | Foundation-wall board with drainage grooves; choose for backfilled walls needing hydrostatic relief. | 0.18 | 0.22 | 3 | — |
SHIPLAPThis page Shiplap / tongue-and-groove edge board | Use where board-to-board joints must block air and thermal bridging without taping. | 0.25 | 0.3 | 3 | — |
Low-GWP HFO / CO₂-blown formulation | Specify for green-building credits and codes phasing out HFC blowing agents; same Type X mechanicals, slightly different aged R. | 0.25 | 0.3 | 3 | — |
GB 8624 B1 fire-rated board | Chinese building code grade with elevated FR loading for façade and roof insulation. | 0.32 | 0.4 | 2.5 | — |
What is C578 Type X SHIPLAP?
C578 Type X SHIPLAP is C578 Type X in the SHIPLAP grade — use where board-to-board joints must block air and thermal bridging without taping. C578 Type X SHIPLAP has a tensile strength of 0.3 MPa (0.0435 ksi), weaker than 94% of polymer grades. The elastic modulus is 0.01 GPa (0.001 Msi). C578 Type X SHIPLAP has a density of 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), lighter than 97% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Advantages
- Lightweight — 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), better than 97% of polymer grades
- Easy to machine — 90/100, better than 95% of polymer grades
- Low moisture uptake — 0.1%, better than 77% of polymer grades
Limitations
- Degrades in UV without stabilisers — 12/100, worse than 99% of polymer grades
- Poor heat conductor — 0.03 W/m·K (0.0168 BTU/hr·ft·°F), worse than 98% of polymer grades
- Low stiffness — 0.01 GPa (0.001 Msi), worse than 84% of polymer grades
C578 Type X SHIPLAP properties
Typical room-temperature values for C578 Type X SHIPLAP; 17 are specific to this condition. Other listed values are C578 Type X reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
C578 Type X SHIPLAP has a density of 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), lighter than 97% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical9
C578 Type X SHIPLAP has a tensile strength of 0.3 MPa (0.0435 ksi), weaker than 94% of polymer grades. The elastic modulus is 0.01 GPa (0.001 Msi).
Thermal8
C578 Type X SHIPLAP is rated for continuous service to 74°C (165 °F). It conducts heat at 0.03 W/m·K (0.0168 BTU/hr·ft·°F), worse than 98% of polymer grades. Thermal expansion is 70 µm/m·K (38.9 µin/in·°F).
Electrical4
C578 Type X SHIPLAP has an electrical resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental2
UV resistance is not recommended.
Sustainability3
Producing a kilogram of C578 Type X SHIPLAP takes about 105 MJ of energy and emits 5 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 10%.
Manufacturability3
C578 Type X SHIPLAP's machinability is excellent (90/100, better than 95% of polymer grades); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C578 Type X SHIPLAP
Is C578 Type X easy to machine?
Cut with hot wire, sharp knife or fine-tooth saw; routing and CNC hot-wire shaping are easy but generate static-clinging dust — vacuum extraction helps.
Can C578 Type X be welded?
Not weldable in the metal sense; boards are joined by shiplap laps, tape, foam-safe adhesive or mechanical washer fasteners, and can be hot-plate/heat fused only in specialist panel lines.
Can C578 Type X be formed, bent or molded?
Produced by tandem extrusion of PS melt with dissolved blowing agent through a slot die into a calibrator; downstream shaping is limited to cutting, grooving and skiving — no post-forming.
What surface finishes work on C578 Type X?
Never leave exposed to sunlight; overcoat with cementitious base coat/EIFS on planed board, or cover with cladding, and use only water-based or XPS-compatible (solvent-free) adhesives, membranes and mastics.
C578 Type X chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| blowing agent (CO₂, HFO-1234ze, HFC-134aresidual cell gas + dissolved agent | 1.5 – 6 | 3.5 |
| flame retardant (polymeric brominated st | 0.7 – 3 | 1.5 |
| nucleating agent (talc) | 0.1 – 1 | 0.4 |
| pigment / IR attenuator (carbon, graphit | 0 – 1.5 | 0.3 |
| polystyrene (general-purpose PS, virgin matrix resin | ≥ 90 (balance) | — |
C578 Type X SHIPLAP — frequently asked
What is C578 Type X SHIPLAP used for?
C578 Type X SHIPLAP is typically used for heavy structural fill under slabs, high-load roof and deck insulation, protected membrane roofs with paver ballast, parking and plaza deck insulation, airport and highway pavement insulation and freezer and cold-storage floor insulation. In short: highest-load XPS grade; shiplap and HFO options; cut-only, no post-forming.
What is the tensile strength of C578 Type X SHIPLAP?
C578 Type X SHIPLAP has a typical tensile strength of 0.3 MPa (0.0435 ksi) — weaker than 94% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is C578 Type X SHIPLAP easy to machine?
Yes — machinability is rated excellent (90/100, better than 95% of polymer grades). Cut with hot wire, sharp knife or fine-tooth saw; routing and CNC hot-wire shaping are easy but generate static-clinging dust — vacuum extraction helps.
Can C578 Type X SHIPLAP be welded?
Not weldable in the metal sense; boards are joined by shiplap laps, tape, foam-safe adhesive or mechanical washer fasteners, and can be hot-plate/heat fused only in specialist panel lines.
What surface finishes work on C578 Type X SHIPLAP?
Never leave exposed to sunlight; overcoat with cementitious base coat/EIFS on planed board, or cover with cladding, and use only water-based or XPS-compatible (solvent-free) adhesives, membranes and mastics.
Can C578 Type X SHIPLAP be formed, bent or molded?
Produced by tandem extrusion of PS melt with dissolved blowing agent through a slot die into a calibrator; downstream shaping is limited to cutting, grooving and skiving — no post-forming.
What is the maximum service temperature of C578 Type X SHIPLAP?
C578 Type X SHIPLAP is rated for continuous use to about 74°C (165 °F), and briefly to 85°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM C578 — Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation — ASTM International (2022)
- GB/T 10801.2 — Extruded polystyrene board (XPS) for thermal insulation — SAC (2018)
- Extruded polystyrene insulation board technical data (FOAMULAR / STYROFOAM class products) — Owens Corning / DuPont Performance Building Solutions (2023)
- Handbook of Polymeric Foams and Foam Technology — Hanser (2004)
- Rigid polystyrene foam property and LCA records — Granta / ICE inventory (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.