Clay drybuilding


Wood fibreboards (HFA) for planking wood and metal post and beam constructions within interior walls, facing, ceiling and roof surfaces. CLAYTEC HFA maxi boards are lightweight and breathable. The large size of 125 x 1.875 cm ensures efficient work and is perfectly suited for the 62.5 cm drywall grid. With the cost-effective larger boards, ecological drywall construction is affordable for everyone!

Field of application
Wood fibreboards (HFA) for planking indoor wood and metal post and beam constructions. For interior walls, facing, ceiling and roof surfaces in drywall construction. As a substrate for CLAYTEC clay plasters.

Wood fibres (wood certified in accordance with the guidelines of the FSC© (Forest Stewardship Council©).

Material parameters
Bulk density 250 kg/m3, compressive strength ≥ 150 kPa, thermal conductivity value 0.05 W/mK, µ 5, spec. thermal capacity 2,100 J/kgK, fire behaviour according to DIN EN 13501-1: E

Building component parameters (certified)
Sound insulation: 41 dB (dividing wall). 54 dB (dividing wall with sep. substructure).

Dimensions and weight
125 cm x 187.5 cm = 2.34 m2, thickness = ≥ 25 mm. Weight approx. 6.25 kg/m2 = approx. 14.6 kg/board

Supply form
Shrink-wrapped on pallets of 45 units

Store resting on pallets; keep straight and dry. Protect edges from damage.

Material needs
When calculating amount required, allow about 10% extra for wastage etc.

Walls: axial spacing 62.5 cm (= 125 cm/2, 187.5 cm/3). Ceilings: axial spacing 41.67 cm (= 125 cm/3) Timber frames e.g. 8 x 5 cm, metal frames e.g. Protektor, Knauf, Rigips, Intraprofil according to DIN EN 18182-1 / DIN EN 14195 or Protektor Maxi-Tec.

You are strongly advised not to attach the material directly to load-bearing parts of the building (e.g. rafters, beams). ATV DIN 18334:2016-09 applies with regard to the maximum moisture content of substructure wood.

Moisture stresses arising from plasters and screeds installed when wet are not permitted. The relative humidity during storage and after installation should not generally exceed 70%. Entry of moisture via the plasterwork must be kept as low as possible.

The boards can be cut to size with a jigsaw or handheld circular saw, for example: see the clip at
The glued layers may separate if cutting strips of board less than 3 cm wide.

The side on which the product name is not printed must face the room. The lowest row of boards must be fitted with a gap to the floor. The panels are abutted against the substructure. They can be installed upright or flat. Cross joints and the extensions of wall opening boundaries using horizontal or vertical joints are prohibited.

Attached to wood using CLAYTEC clayboard screws 5 x 50 mm or WÜRTH drywall screws with coarse thread. Attached to metal using WÜRTH drywall screws with drill bit or KNAUF universal screws FN 4.3 x 35 mm. Screw spacing approx. 20 cm (for walls approx. 28 screws per board / approx. 12 screws per m2).

Staple fastening on the whole surface of wood with BEA 16/35_NK_HZ, on wooden frames with 155/50_V2_HZ (if thick layer coating is planned 155/65_V2_HZ).
Twice as many staples should be used compared to screws (see above); spacing from the edge 10-15 mm.

In bathrooms, use rustproof fasteners only

Subsequent processing
The unprinted side should be plastered. If necessary, fill gaps of ≥ 1 mm in width with CLAYTEC clay adhesive and reinforcing mortar or clay topcoat fine 06 and leave to dry. Carefully dust boards.

Thin layer coating: The surfaces are coated with a 3 mm layer of clay adhesive and reinforcing mortar. This can also be sprayed on using a plastering machine; if this application method is used, rest periods are not necessary. Flax or glassfibre meshes are spread flat and worked into the surface while it is still wet. Properly apply YOSIMA clay designer plaster after drying. Apply the reinforcement layer very carefully for YOSIMA
colour clay surfacer
or CLAYFIX clay paint system (= fill the drill holes and indentations before starting and allow these points to dry); it is more advisable to apply a thin layer of clay topcoat fine 06.

Thick layer coating: Pre-treat the areas with RED primer. Apply clay undercoat plaster with straw, clay plaster mineral or SanReMo to the walls in a layer thickness not exceeding 8 mm and to ceilings or sloping roof surfaces in a layer thickness not exceeding 5 mm. Flax or glassfibre meshes are spread flat and worked into the surface while it is still wet. Leave to dry. Total thickness of the plaster structure is 15 mm at max. for walls and 10 mm at max. for ceilings and inclined roofs (at least two layers in each case).

Wall panel heating: Prepare the areas with RED primer or by notched plastering using clay adhesive and reinforcing mortar. Leave to dry. Before starting, spray one of the above clay mortars onto the surface to a maximum thickness of 8 mm. After drying, fill the gaps as far as the pipe clamp for the wall heating. Apply heat to dry the entire basecoat layer. For further instructions, refer to the CLAYTEC clay plasters worksheet.


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