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FAQ


Wall covering hanging

A: What steps are involved?

  • Prepare the wall. The wall must be sound, clean and dry.
  • Trace a vertical line on the wall at a distance from the starting angle of the room equal to the width of the wall covering less about 3 cm.
  • Cut several lengths of covering 5 to 10 cm longer than the total height of the wall. Number them.
  • Apply adhesive to the wall over a section 5 cm wider than the covering.
  • Use a notched spatula to apply a uniform coat of adhesive. Use a paint brush to apply adhesive in vertical angles and at the top and bottom of the wall.
  • Lay the covering on the wall leaving a few centimeters excess length at the ceiling. Adjust its position by sliding. Modern adhesives provide exceptional slip for easy, accurate positioning.
  • Smooth the covering by running a flexible plastic scraper over it to ensure good adhesion and evacuate air bubbles.
  • Trim the covering in the angles (along the ceiling and skirting, floor or door-top):  hold a wide metal spatula (or wall scraper) very firmly in the angle, then use a sharp cutter to trim.
  • Join adjacent widths. You can lay widths carefully edge-to-edge or use the double-cut method.
  • Double-cutting consists in overlapping the covering by about 4cm over the previous width. Then cut through the double thickness at about 2 cm from the edge (at the center of the overlap) using a sharp cutter pressed against a metal straightedge. Remove the two cut-off strips then press down the two edges which will match perfectly.
  • In the event of a serious positioning error, the best solution is to remove the last length of covering and start over.
  • Remove traces of adhesive immediately using a clean damp cloth.
  • Clean the tools: wash tools in water immediately after use.

B: Which face should be glued?

Apply the foam side of the covering to the surface.

C: Which adhesive should I use?

Using the right adhesive is vital to hang a wall covering successfully. In general, the suitable adhesive is indicated in the hanging instructions. Otherwise ask your supplier for advice.

D: How do I prepare the surface?

The preparation phase is important when hanging wall coverings. The surface must be clean, dry, stable, flat and normally absorbent:

  • Plasterboard: apply a coat of primer paint before hanging the covering.
  • Walls already covered: remove the old covering.
  • Holes and cracks: enlarge the cracks then level them with filler. If necessary, you can use Ultratap rolled coating to help mask flatness defects. 
  • Painted walls: clean thoroughly using a powerful detergent (working from the bottom upwards). Rinse well. Cover lacquer paint with a primer adhesive; for this you can use Kleber adhesive diluted with 20% water applied using a roller.  Leave to dry for 24 hours before hanging the wall covering.

E: How do I cut the Sempatap?

Cutting angle: about 30°

Tool: a sharp break-off blade cutter.

Break off the blade frequently to ensure sharpness. For a result perfect, use a long metal spatula or straightedge to guide the cutter down a wall or in angles.

F: Which spatula should I use to apply the adhesive?

For Sempatap wall coverings use an A2 spatula:

A2 notched spatula: consumption 400 to 500 g/m².

A3 notched spatula: consumption 600 to 700 g/m².

A4 notched spatula: consumption 800 to 900 g/m².

A5 notched spatula: consumption 300 g/m².

G: What is the drying time?

This is the time needed to allow the water in the adhesive to evaporate and ensure definitive adhesion. In the case of water-based adhesives, the water evaporates and is also absorbed by the surface. Drying time is typically 5 to 10 minutes depending on the ambient temperature.

H: How do I ensure good adhesion?

To obtain good adhesion, the adhesive should ideally penetrate into the surface. This requires appropriate preparation of the surface which must be free of grease, dust and grime. Roughen the surface if it is very smooth. Apply a uniform coat of adhesive, then hang the covering applying moderate, uniform pressure using a plastic scraper.
 

I: How do I smooth the covering?

The wall or floor covering must be fully flattened onto the surface. In the case of wallpaper, it is particularly important to remove air bubbles.

Use a plastic spatula to press down the covering with care, first in the vertical direction then from the center of the width towards the edges.

J: How long is the drying time?

Drying time before decoration: 48 hours on an absorbent surface, 4 to 5 days on a non-absorbent (sealed) surface.

 

Finishes applied over Sempatap coverings

After complete drying (48 hours), Sempatap coverings can receive all types of decoration (transparent to sound):  wallpapers and other wall coverings, matt acrylic paint, etc.

Note: we do not recommend vinyl papers and enamel paints since these tend to reflect sound.

Sempaphon Absorb can be painted, provided the entire surface is prepared by cleaning residues. It may be necessary to do this several times in order to obtain a suitable surface. The cleaning must be carried out from the top towards the bottom using a wide large spatula to avoid applying excessive pressure.

How do I finish angles?

Sempatap Corner Strip: an aluminum strip to protect edges and angles.

Applying the Corner Strip: cut the strip to the required length, then bend it according to the height to be covered. Apply a coat of adhesive to the edges or the surface (paper), then leave this to soak in for 2 minutes. Press the Corner Strip firmly into place. If necessary, apply filler after drying.

Can I use roughcast finishes?

Choose a ready-to-use product composed essentially of resins in emulsion, mineral fillers, and cellulose fibers (e.g. Semin, "Murs d’Autrefois" granular wall coatings, etc.).

 

Basic elements of acoustics

Sound absorption and insulation

Sound absorption refers to a reduction of sound energy by materials.

When a sound wave hits a surface, some of its energy is reflected from the surface, some is absorbed. Some materials absorb much more sound energy than others. The coefficient α indicates the difference between the sound energy absorbed and the sound energy reflected:

α  = 0: total reflection (no absorption)

α = 1: total absorption (no reflection)

α = 0.55 means that 55% of the sound energy is absorbed and 45% is reflected.

Sound insulation refers to the ability of a structure to prevent transmission of sound (for example, from one room to another). We distinguish two types of sound insulation :

- Insulation against airborne sound:

When the wave energy emitted by a sound source impinges on a wall, some of it is reflected and some passes through the wall.

- Insulation against the impact noise (footfalls, for example):

It is possible to attenuate impact-type sound passing through the floors of a building. The attenuation is expressed by the index ΔLn,w (dB).