Execution of internal insulation with insulating render

The construction of existing buildings, the renovation of listed facades and the thermal refurbishment of individual flats and storeys regularly require interior insulation solutions. The usual interior insulation solutions with vapour barriers are prone to damage, e.g. due to poor execution or subsequently destroyed vapour barriers. Interior insulation systems with mineral insulating plasters are an economical, safe, proven and durable alternative. The installations of the building services can be accommodated in the insulation plaster layer. These insulation layers can usually be insulated up to a thickness of 60 mm in the interior without verification. Greater thicknesses should be calculated beforehand by a simulation programme (for calculating the coupled heat and moisture transport in building components). The corresponding test certificates can be provided upon request.

Simple & safe to the goal

  1. 1. The U-value is a heat transfer coefficient, indicating the amount of heat passing through 1 m2 of a building element in 1 second when the temperature difference between indoor and outdoor air is 1 K (Kelvin).
    U values of approx. 0.6 W/m2K can be achieved with an insulating plaster in old buildings, even with heavy masonry. Due to the existing capillary conductivity and the jointless insulation, this type of interior insulation is not critical. Moisture calculations might be necessary only in case of insulation thickness
    60 mm.

  2. Preliminary works

    2. In case of load-bearing old plasters, their surface must, as usual, be assessed with regard to the adhesion of the mineral bonding layer to be applied.

  3. 3. Knock off damaged old plasters and scrape out brittle mortar in the masonry joints.

  4. 4. Execution of the installations of the housing services.

  5. 5. Apply a mineral bonding layer (weber.therm 500 or weber.dur 101, according to the substrate porosity) on the old load-bearing plaster surfaces and comb it horizontally with a notched trowel.

  6. Application

    6. Apply the insulating render weber.therm 507 in 2 layers either with a delay of approx. 10 - 20 minutes ("wet-in-wet") or with a delay of 1 day. The thickness of the 1st layer should be 2/3 and the thickness of the 2nd layer 1/3 of the total thickness (max. 20 mm).

  7. 7. After a waiting time of 1 day, per cm thickness roughen weber.therm 507 with a nail float (scraper).

  8. 8. Afterwards, the application of the bonding and reinforcing mortar weber.therm 300 and the woven mesh weber.therm 310 can start.

  9. 9. Depending on the type of overlay plaster and weather conditions, the reinforcement layer must be eventually pre-wetted or pre-treated with the universal primer weber.prim 403.

  10. 10. The textured lime plaster weber.cal 286 is applied up to 2 - 3 mm thickness.

  11. 11. Without delay, work to the texture, using a fine or a coarse sponge float, depending on the desired pattern.