Flatness guide for plaster and render galvanized steel 10mm x 2.5m

Welcome to flatness guide FAQ! Here you'll find answers to our most asked questions. Still can't find quite what you're looking for, or have something we should know? Send us an email, we're happy to help!

• Q1: What is a flatness guide for render?

  A1: A flatness guide for render (also called a render guide bead, screed rail, or plaster guide) is a straight profile fixed to a wall before rendering to control:
  - Render thickness
  - Surface flatness
  - Alignment / level
  - Material consumption
  It acts as a depth and leveling reference so the installer can rule off the render perfectly straight using a darby or straight edge.

• Q2: Where are flatness guides used?

  A2: Common applications:
  - External sand & cement render
  - Monocouche render
  - Silicone / acrylic thin coat systems
  - External Wall Insulation (ETICS / EWI)
  - Internal plaster basecoats

• Q3: Do I need guide rails when rendering a wall?

  A3: No — guide rails (flatness guides / screed rails) are not always mandatory, but in most professional rendering they are strongly recommended to achieve consistent thickness and a flat finish.

• Q4: How to set render beads level on a wall?

  A4: Setting render beads (flatness guides / screed rails) level and plumb is the most critical stage of rendering — it determines the final wall flatness and thickness accuracy.
  Before fixing any beads, define the finished wall line. Always start with:
  - External corners
  - Wall ends
  - Window/door reveals
  These become your alignment reference.

• Q5: What is the correct spacing for render guides?

  A5: Render guides (flatness guides / screed rails) are typically spaced 1.2 m to 1.5 m apart, depending on the length of the straight edge (darby / rule) used to level the render.

• Q6: Do you remove render guides after plastering?

  A6: The strips should be removed from the wall before the plaster dries. Note: Do not leave the strips in the wall due to the potential corrosion of galvanized steel in the aggressive chemical environment of gypsum plaster mortars.

Welcome to polystyrene insulation EPS boards FAQ! Here you'll find answers to our most asked questions. Still can't find quite what you're looking for, or have something we should know? Use Q&As section or send us an email, we're happy to help!

• Q1: What are EPS polystyrene boards used for in external wall insulation?

  A1: EPS (Expanded Polystyrene) boards are used as thermal insulation in External Wall Insulation (EWI) systems. They are mechanically fixed and adhesively bonded to external walls, then reinforced with basecoat, mesh, and decorative render to improve energy efficiency and façade appearance.

• Q2: Is EPS insulation good for external walls?

  A2: Yes — EPS is one of the most widely used façade insulation materials because it offers:
  - Excellent thermal performance
  - Lightweight handling
  - Cost efficiency
  - Easy cutting and installation
  - Compatibility with most render systems

• Q3: What thickness EPS boards are used for EWI?

  A3: Common thicknesses in the UK:
  - 50 mm – minimal upgrade
  - 70–90 mm – standard retrofit
  - 100 mm – popular energy upgrade
  - 150–200 mm – low-energy / passive targets
  Thickness depends on U-value requirements and building regulations.

• Q4: What is the thermal conductivity (Lambda) of EPS?

  A4: Typical EPS lambda values:
  - EPS 70: ~0.038 W/mK
  - EPS 80: ~0.036–0.038 W/mK
  - Graphite EPS: ~0.031–0.033 W/mK
  – IBB - Thermonium Plus has the highest Lambda 0.031 W/mK

• Q5: Is EPS insulation fire resistant?

  A5: Standard white EPS is Euroclass E (combustible).
  However:
  - It is always encapsulated within render systems.
  - Fire-retardant grades are used.
  - System fire ratings depend on the full EWI build-up.
  For high-rise buildings, mineral wool may be required.

• Q6: How long does EPS external wall insulation last?

  A6: Properly installed EPS EWI systems last 30–50 years+ with maintenance of the render finish.