Oikodomisis

Thermal Facade Checklist: How to Check Your Contractor

One of the biggest worries of any homeowner proceeding with an energy upgrade is the reliability of the crew. In construction, there is a saying: "A good worker shows his quality before the render goes on". Once the mesh and render cover the polystyrene, everything looks perfect and defects hide.

To ensure your money is well spent, you don't need to become an engineer. Just make 5 targeted "visits" to the site and check the following 5 points.

Check 1: Before the Adhesive (The Wall)

Visit the site on the first day the scaffolding goes up.

  • Cleaning & Loose Material: Have they scraped off peeling old render? Did they wash the wall of mould and dust?
  • Primer: Did you see them coating the wall with a liquid (primer) before starting to bond? If they are gluing directly onto dusty brick or old paint, stop them.
Wall check before bonding - primer and cleaning

Check 2: The Bonding Moment (The Trowel)

Stand beside the worker as he applies adhesive to the board (EPS/XPS).

❌ No "Cookie Dough" Dabs

Is he applying adhesive with just 4-5 blobs in the centre, leaving edges bare? WRONG.

✅ The Correct Frame

Adhesive must go around the entire perimeter of the board (like a frame) plus 3 dabs in the centre. Or, if the wall is perfectly flat, spread over the entire surface with a notched trowel.

Check 3: Building on the Wall (The Puzzle)

Look at the wall from a distance, after enough boards are bonded, but before fixings go in.

  • Staggered (Running Bond): Do the vertical joints form crosses (+)? WRONG. They should be laid like bricks (each joint offset at least 20cm from the one below).
  • Building Corners: At external corners, do the boards "interlock" alternately like a zipper?
  • Windows (The "L" cut): Around window corners, has a single board been cut in an "L" (pistol) shape? Or did they join two boards exactly at the corner? If the latter, your render will crack guaranteed.
  • Gaps: Are there gaps larger than 2mm between boards? If yes, insist they are filled with polyurethane foam and NOT adhesive/filler!
EPS boards staggered, corner zipper, L-cut at window

Check 4: The "Nailing" (The Fixings)

  • The Count: Count the plastic fixings. Are there at least 6 per square metre (or more at corners and high points)?
  • Countersinking: Does the fixing head protrude from the polystyrene? WRONG. It must be flush with the board. Ideally, it has been sunk deeper and covered with a polystyrene cap to avoid a thermal bridge.
Fixings countersunk flush in EPS

Check 5: The "Sensitive Zones" (Base and Windows)

📐 The Plinth

In the first 30-50cm above ground, did they install the hard (coloured) XPS, or did they run the soft white EPS all the way down? If the latter, moisture will destroy you.

🪟 The Reveals

Did they install thin insulation (2-3cm) inside the window opening or leave the wall bare to save time? Did they apply self-expanding tape (Compriband) between the EPS and the aluminium?

The 10x10 Model Experiment

10x10 experiment - indifferent vs informed homeowner

How much does quality change?

❌ The Indifferent Homeowner (Scenario A)

Agrees on the price, hands over the keys and goes on holiday. The crew works fast. They apply adhesive in dabs ("cookies"), skip fixings to save money and leave gaps. They render. The owner returns, the house looks stunning and he pays. At the first strong north wind, the wall leaks cold, 3 square metres detach and mould appears at the windows.

✅ The Informed Homeowner (Scenario B)

Prints this checklist. On the first day he sees the worker applying adhesive wrong. He shows him the manufacturer's datasheet and insists on perimeter bonding. He checks the "L" cuts at the windows. The crew realises the client "knows" and works exactly to specification. The thermal facade lasts 30 years without the slightest crack.

The Final Conclusion: Good professionals are not annoyed when the homeowner asks questions. On the contrary, they are pleased because their quality work is recognised. Use this checklist not as a "policing" tool, but as a quality guide to protect the biggest investment you make in your home.

Related Articles

Material (CE) and System certifications: What papers to ask for Application conditions: Temperature and humidity during construction Insulating window reveals (frame casings) Integrating downpipes and cables into external insulation

Application & Construction Details: Correct Installation Guide

Return to category.

Go to category

Preview