Building a Raised Ceiling with ECMIL Steel Purlins,
Plyfoil, Colorbond Sheeting & T1-11 Boarding

Key Components and Their Roles

ECMIL Z and C Purlins
These cold-formed galvanised steel purlins are engineered for lightness, strength, and precision.

• C Purlins are ideal for vertical wall studs and end rafters.
• Z Purlins, with their interlocking flanges, allow for continuous runs across spans with easy overlaps, ideal for rafters in roof construction.
  
  Both are available in a variety of gauges and lengths, ensuring custom fitment across different spans, typically resting on a perimeter steel or concrete frame.

Colorbond Roof Sheeting
A high-performance pre-painted steel, Colorbond is durable, fade-resistant, and comes in a wide range of colours. Manufactured with a Zincalume base, it provides superior corrosion resistance in coastal or tropical climates.
The sheets are lightweight, easy to install, and strong enough
to withstand high wind loads common in the Caribbean.

Plyfoil Radiant Barrier Insulation
Plyfoil is a double-sided reflective insulation material made from polyethylene bubble core sandwiched between two layers of aluminum foil.
Benefits include:

• Reflects up to 97% of radiant heat.
• Reduces ceiling temperatures significantly.
• Serves as a moisture and vapor barrier.

T1-11 Boarding (Grooved Plywood Siding)
T1-11 provides the exposed interior finish. It’s structural, allowing it to act as the ceiling, and decorative, with its grooved wood-grain look. It can be stained or painted and fastened directly to purlins with appropriate spacers and insulation gaps.

Benefits of This Construction System

• Structural Strength with Lightweight Design
  ECMIL purlins provide load-bearing support with less weight compared to timber rafters. This reduces dead load on the building’s foundation and allows for longer spans without internal supports.
• Hurricane Resistance
  Steel framing combined with secure fasteners and Colorbond’s interlocking sheets resists uplift, impact, and shear forces, outperforming traditional roofing in storm-prone zones.
• Heat Reflection & Thermal Comfort
  Plyfoil insulation dramatically cuts down solar radiation passing through the metal roof, lowering interior temperatures and reducing reliance on air conditioning.
• Cost Efficiency
  Steel and Plyfoil reduce construction time, maintenance, and cooling costs. T1-11 eliminates the need for additional interior cladding.
• Sustainability
  Steel and aluminium components are recyclable,
  and the reduced energy needs for cooling add long-term eco-efficiency.

Layered Cross-Section Description

Below is a simple layer-by-layer explanation from top (outside) to bottom (interior ceiling view):

Colorbond Roof Sheeting

• Fixed directly to top flanges of ECMIL Z or C purlins using hex-head fasteners with neoprene washers.
• Overlapped horizontally and vertically to ensure water-tightness.

Plyfoil Insulation

• Rolled over the top surface or underside of the purlins depending on preference and space.
• Fixed using reflective tape or metal strapping, maintaining an air gap below the roof sheeting to maximize radiant barrier effect.

Steel Purlins (Z or C Type)

• Spaced as per engineering spec (usually 900–1200 mm apart).
• Mounted perpendicular to the slope or span direction.
• Provide structural integrity and anchoring for both roofing above and ceiling panels below.

T1-11 Boarding (Ceiling Finish)

• Attached directly to underside of purlins using screws or nails.
• May be pre-finished or painted/stained in place.
• Provides a clean, rustic, and durable ceiling with minimal maintenance.

Construction Process

Framing and Purlin Layout

• Establish the perimeter frame using concrete
  or structural steel.
• Determine purlin spacing based on span load
  and ceiling weight.
• Install ECMIL Z purlins for rafters, optionally
  using C purlins for vertical studs or perimeter connection.
• Ensure overlaps in Z purlins are properly nested and secured with bolts or self-drilling screws.

Install Plyfoil Insulation

• Measure and cut Plyfoil to span across
  the underside of the roof.
• Secure with reflective tape or strapping.
• Maintain 1 to 2 inches air gap between Plyfoil 
  and the roof sheeting for optimal performance.

Fix Colorbond Roofing

• Lay Colorbond sheets from the eaves to the ridge.
• Fasten using roofing screws with seal washers into top purlin flanges.
• Seal all overlaps with butyl tape or silicone sealant if extra waterproofing is required.

Install T1-11 Boarding

• Cut T1-11 sheets to fit between purlin spans.
• Lift and fasten from the center outwards to prevent sagging.
• Paint or stain before installation, or do a finishing coat afterward.

Final Touches

• Add ridge cap and eave flashing.
• Optional: integrate lighting or wiring channels
  behind T1-11.
• Conduct final inspection for fastener tightness and insulation fit.