Walls, roofs and floors: what goes where and why

On this page: Timber frame wall · Wall from the inside — renovation · Pitched roof — new · Roof from above — renovation · Floor · Why the tapes matter so much · ESB

Four jobs, four layers

Every wall, roof and floor has four jobs to do. Each is done by a separate layer, and no layer does another one’s job.

The rule: airtight inside, open outside. Each layer further out lets vapour through more easily than the one before, so that moisture can get out instead of collecting in the construction.

Timber frame wall

Outside, a naturheld board stops the wind, FLEX between the studs keeps the heat, and on the inside there are two good solutions.

ELKA esb Plus → · ELKA VITA → · AIRSTOP DIVA →

Wall from the inside — renovation

When the facade cannot be touched — an old house, a flat, a stone wall. The board is glued over its whole area to the dry wall, without a vapour barrier: together with the capillary-active plaster it takes up moisture and returns it to the room.

In detail (in Bulgarian): insulating from the inside →

Pitched roof — new

FLEX between the rafters, a naturheld board above them — a second protection against rain and no thermal bridges through the rafters. Inside — a taped vapour control layer.

Roof from above — renovation

The old roof stays and the rooms below are not opened. The tiles come off, a membrane and a 6–8 cm naturheld board go on the old roof, then new battens and the tiles go back.

Floor

A warm floor that does not drum — on a concrete slab or on joists with a ventilated space below. Instead of ESB and floorboards, VITA 27 mm can go straight on — it is also the finished floor surface.

naturheld 110 → · ELKA VITA → · OMEGA MONOTOP 330 →

Work it out for your area in the calculator → · Check the wall in the generator →

Why the tapes matter so much

Wood fibre boards insulate, but they are not airtight — under DIN 4108-7 they count as porous. Airtightness comes from a separate layer on the room side: a vapour control membrane or taped boards.

That layer is only as airtight as its weakest joint. A membrane with untaped overlaps, or boards with open joints, let warm, humid air through the gaps — exactly where the insulation is coldest.

That is why the tape is not an extra but part of the layer. Tape: membrane overlaps, joints between boards, connections to walls, floor and ceiling, every pipe and cable penetration, windows, chimneys and roof windows.

The airtightness of the finished building is checked with a Blower Door test — it is easier to get it right the first time than to hunt for gaps once the lining is closed.

Airtightness and the Blower Door test →

naturheld FIX 60 tape (60 mm × 25 m): €26.66 incl. VAT per roll.

ESB — the board that carries and seals

• A class P5 structural board — load-bearing, for humid conditions. It braces the wall studs, the roof and the floor and is the base for the next layers.
• On the room side it can also be the airtight layer: the tongue and groove boards fit tightly, and the joints and connections are taped.
• It lets water vapour through 2.5 to 4 times more easily than OSB (µ 80/40 against 200/150) — the construction can dry out instead of holding moisture.
• Formaldehyde ≤ 0.03 ppm, no isocyanates, Blue Angel certified — suitable for living spaces.
• With tongue and groove it is also recognised as a roofing underlay board under the rules of the German roofers’ association (ZVDH).

ELKA esb Plus → · ESB vs OSB — the comparison in numbers →

What goes where — in short

Questions