Clay drybuilding


Thin wood fibreboard (HFA) as a plaster base on wood and wood-based materials. The boards can be screwed or stapled into place. This creates a safe and simple substrate on wood for the reinforcing layer of clay adhesive and reinforcing mortar and the subsequent clay finish.

Field of application
Wood fibreboard (HFA) as a plaster base in timber constructions for CLAYTEC clay plasters

Material parameters
Bulk density 230 kg/m3, compressive strength ≥ 100 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

1.20 m x 0.60 m = 0.72 m2. Thickness = 8 mm
Supply form 276 boards/1-way pallet

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

Material needs
Take a reserve of approx. 10% into account for offcuts when determining the material needs.

The substrate must be stable, frost-free, dry, clean (wooden composite boards, dust-free), free of salt, sufficiently rough and absorbent. Roughly repair any defects. You may have to fix sanding substrates with CLAYTEC deep penetrating primer and stabiliser.

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%. Keep the entry of moisture through gluing and plasterwork as low as possible.

The boards are curt with a jigsaw, circular hand saw or cutter. The lowest row of boards must be fitted with a gap to the floor. The side on which the product name is not printed must face the room.

The boards are fastened in place without gluing using CLAYTEC clayboard screws 5 x 50 mm, WÜRTH drywall screws with coarse thread or KNAUF universal screws FN, space between screws approx. 20 cm, or closer if there is to be a subsequent thick layer coating. Suitable staples include BEHRENS (BEA) 155/18_NK_HZ, Art. no. 10002009, or similar. Spacing between staples approx. 9 cm, distance to edges 10-15 mm.

Always use stainless fastening materials in bathrooms.

Horizontal or vertical joints must not be continuations of the borders of wall openings. Lay the boards with joints that are offset by at least 20 cm, or even better 30 cm. 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.