TEP ROOF OY · MATERIAL AND INSTALLATION GUIDE
Mineral wool roof insulation
Here, a mineral wool substrate means the roof insulation beneath the waterproofing. It is distinct from the load-bearing metal, concrete or timber structure. The function and position of the board determine the product required.
Which mineral wool solution?
- Glass wool and stone wool board and lamella insulation products are available for low-slope roofs. The lower and intermediate layers provide most of the thermal insulation; the top layer forms the waterproofing substrate. Products must not be interchanged on thickness alone.
- A separate suitable mineral wool board may be needed above profiled metal decking to support the vapour control layer. This sits below the main insulation layer. A building board specified in the design may be an alternative. Any levelling or support layer on a concrete substrate is specified separately.
Which properties should be compared?
- Compare the thermal performance, build-up height and load resistance of the entire insulation combination. Roof traffic, equipment and solar panel supports impose different loads. A product's CS(10) compressive strength alone is not the permissible service load for the roof.
- Check reaction to fire in the documentation for the named product; the term mineral wool alone does not establish a class. Check the waterproofing and substrate combination too. The insulation product classification does not in itself demonstrate the fire resistance of the whole roof assembly.
Vapour control and drying
- In a conventional mineral wool roof over a heated space, the vapour control layer is on the warm side of the main insulation. The water vapour permeability of mineral wool does not replace the need for a vapour control layer. Design its support, joints, edge connections and penetrations as a continuous sealed layer.
- Where the solution uses insulation with ventilation grooves, the grooves, collector channels and openings to outside air must form a continuous system. Grooves do not repair a roof leak or make it acceptable to cover wet insulation.
Check on site
- At acceptance, check product identifiers, thicknesses, layer sequence, substrate evenness and insulation dryness. Fit boards tightly and stagger joints between layers in accordance with the manufacturer's instructions. Maintain ventilation routes through junctions as well.
- Protect storage areas and access routes, and size each day's work area to suit weather protection and waterproofing progress. Before covering, check vapour control joints, insulation surface condition and the specified fixings. Record deviations and corrective work.
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.
- Saint-Gobain Finland Oy / ISOVER: Low-slope roofs: system guide 07/2026, pp. 5-7, 11 and 23 Checked 19.10.2026
- Saint-Gobain Finland Oy / ISOVER: OL-TOP: top and base insulation boards, use and installation Checked 19.10.2026
- ROCKWOOL Finland Oy: Low-slope roofs, 1 March 2024: layers and installation, pp. 4-12 Checked 19.10.2026