TEP ROOF OY · MATERIAL AND INSTALLATION GUIDE
Vapour control on a concrete deck
On a concrete roof deck, the slab type, surface and moisture condition, and ventilation of the build-up above affect vapour control selection. A concrete surface alone does not establish airtightness at junctions.
Start the comparison with a bituminous membrane
- A bituminous vapour control membrane suitable for a solid concrete substrate is a natural starting point for quotation comparison. Available options include BH1-class products with welded laps. Fixing the membrane and closing its joints are separate operations; fully bonding every membrane must not be assumed.
- A self-adhesive bitumen-aluminium vapour control layer is an option where the concrete substrate and roof build-up suit that system. It requires product-specific priming and careful pressure application at joints. A self-adhesive surface does not remove requirements for substrate cleanliness, dryness or working conditions.
When can a film be considered?
- A reinforced or aluminium-laminated plastic vapour control layer may be suitable if its technical properties and sealing system meet the project requirements. Films with high water vapour resistance use system-compatible sealing tapes; include joints and penetrations in the product comparison.
- Kattoliitto recommendations distinguish solid, hollow-core and double-tee slabs, as well as moisture exposure. For example, BH1- or BHA2-class bituminous vapour control layers are the starting point for a poorly ventilated concrete roof with a high moisture load; a plastic system must meet the project-specific technical requirements. Ordinary PE film is not a universal substitute.
Substrate acceptance is critical
- Inspect the surface before covering: remove dust that impairs adhesion, loose material and sharp projections, and prepare the surface for the selected system. Agree the primer, drying and adhesion checks according to the manufacturer's instructions.
- Construction moisture remaining in concrete needs a controlled drying route. Agree moisture measurements and conditions for covering as part of the project design; surface dryness alone does not describe the condition of the whole slab. Also assign responsibility for sealing precast joints and wall connections.
Include in your request for a quotation
- State the slab type, roof build-up, area, indoor use and known moisture conditions. Attach substrate acceptance information, a roof section and junction drawings. Clearly identify measurements or designs that are still outstanding.
- Request options for the same scope: substrate preparation, priming, vapour control layer, edges, penetrations and protection. Agree stage inspection points and records of the vapour control layer before insulation is installed. For refurbishment, distinguish retained layers from those to be replaced.
Use and design responsibility
TEP Roof Oy guide cards support project preparation and the definition of contract scope. They are not project-specific construction designs. The project structural designer is always responsible for checking the suitability of the solutions presented and adapting them to the project's structures, loads and requirements. Construction requires project-specific design and approval, together with the current manufacturer's instructions for the selected products.
Sources
An editorial compilation by TEP Roof Oy. The product- and system-specific source instructions must be checked for the selected solution.
- Kerabit Oy: Bituminous vapour control membranes: solid substrates and bituminous options Checked 19.10.2026
- BMI Suomi Oy: Products for low-slope roofs: bituminous and reinforced aluminium-laminated vapour control layers, p. 8 Checked 19.10.2026
- Oy Sika Finland Ab: Sarnavap-5000 E SA: self-adhesive vapour control layer, Finnish product data sheet, 05/2020 Checked 19.10.2026
- Kattoliitto ry: Toimivat katot 2025 (Functional Roofs): vapour control layer substrate, installation and application classes, pp. 20-26 Checked 19.10.2026