Direct answer: a reliable aluminium-plastic underfloor-heating installation is a traceable sequence, not a single gauge reading at the end. Confirm the base, insulation, manifold, circuit labels, spacing, bends, fixing, first pressure test, concealed acceptance, backfill and curing in that order. Before each covering-up step, leave a record that another party can check. Test pressure and hold time must come from the design documents and applicable codes; this page does not invent a site value.
- Keep buried runs free of joints unless the project documents define a recorded exception.
- Use the minimum bend radius in the technical data for the relevant grade; inspect every bend for whitening, wrinkles or creases.
- Record circuit number, measured length, pipe identification, bend observation, gauge reading, start and end time, ambient temperature and sign-off.
- Complete a pressure test and sign-off before concealment, then record the post-backfill re-test as well.
- Installation method, test parameters and acceptance criteria remain governed by the design documents and locally applicable requirements.
Eight stages and what each leaves behind
| Stage | What happens on site | What goes in the file |
|---|---|---|
| 1. Base and insulation | Check levelness, lay insulation boards and the reflective layer | Photographs before concealment and a base acceptance record |
| 2. Manifold positioning | Confirm height, circuit allocation and service access | Circuit-number schedule matching the labels on the loops |
| 3. Setting out and laying | Lay to design spacing; add density on cold edges where specified | Measured spacing by zone, not a uniform “experience” layout |
| 4. Bending | Radius per the grade's technical data; aluminium multilayer holds a set, all-plastic springs back more | Measured radius and appearance check; whitening, wrinkles or creases mean stop and review |
| 5. Fixing and movement | Clip or mesh spacing, perimeter insulation, separation joints in large areas | Photographs of the fixing method and spacing |
| 6. First pressure test | Pressure and hold time per design documents and codes | Gauge reading, start and end time, ambient temperature, signatories |
| 7. Concealed acceptance | Inspect and sign off before backfilling | Concealed-works form with loop photographs and matching numbers |
| 8. Backfill and curing | Protective layer, strength and moisture control; coordinate the finish sequence | Backfill mix record and curing log |
Four site disciplines that prevent rework
No joints in the screed. A joint is almost impossible to inspect after backfilling, so any exception must be agreed and recorded in the project file. Protect the oxygen barrier. Where the outer layer is co-extruded with EVOH, scratches and prolonged outdoor storage weaken the barrier; do not leave an uncoiled pipe exposed to trampling for long. Confirm diameter and turning space at design stage: a pipe that “will not turn” on site usually signals a conflict between diameter, bend radius and build-up thickness, not a careless crew. One pressure test is not enough: keep both the pre-concealment record and the post-backfill re-test.
What the acceptance record must contain
| Field | Why it matters |
|---|---|
| Circuit number and measured length | Checks design alignment and underpins pressure-loss and balancing review |
| Pipe identification: structure, outside diameter × wall, coil length, batch | Aligns the installed material with samples, shipping documents and test reports |
| Measured minimum bend radius and appearance | Shows whether the aluminium and adhesive layers may have been affected by bending |
| Test pressure, hold time and pressure drop | The only reviewable acceptance object; values come from design and codes |
| Environment and backfill condition | Basis for later review of cracking and curing |
| Photographs and sign-off | Basis for responsibility allocation and cross-border claims |
Where the supplier fits without replacing site responsibility
A verifiable supply record can identify the pipe structure, outside diameter × wall thickness, coil length and batch, with permanent coil marking and accompanying information. Factory inspection does not certify the installation: workmanship, test parameters and acceptance criteria remain set by the design documents and local requirements. For loop quantities and zoning, see the quantity guide; for the material difference in bending and shape retention, see the STABIL explainer.
Scope and limits
This article is for distributors, installation contractors and project teams aligning site workflow and evidence before concealment. It is not a construction-quality promise or a code conclusion. Requirements vary by country and project, so the design documents, contract annexes and local rules govern. This page deliberately gives no numerical test pressure or hold time.
Sources
- EN 1264 — embedded heating and cooling systems: use the current official edition (CEN).
- EN ISO 21003 — multilayer piping systems: use the current official edition (ISO).
- DIN 4726:2024-12 — oxygen-barrier requirements and test framework (DIN Media, retrieved 30 September 2026).
- СП РК 4.02-101-2012, СП РК 2.04-01-2017, СН РК 2.04-21-2004 — Kazakh design framework (adilet.zan.kz, retrieved 1 October 2026).
Frequently asked questions
Can the final pressure record replace the first test?
No. The pre-concealment test and the post-backfill re-test document different stages and both should be filed.
What bend radius should the crew use?
The minimum bend radius in the technical data for that grade. Do not import a radius from another pipe system or use a generic value without a document.
What pressure and hold time go on the form?
Only the values given by the project design documents and applicable codes. This page intentionally gives no numerical recommendation.
What should happen when a bend is white or wrinkled?
Stop that part of the work, isolate the record and ask the designer or pipe manufacturer for a decision; it should not be accepted on a visual “looks fine”.
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