ᐅ Renovation of a 1972 Prefabricated House by Okal with a Completely New Wall Construction

Hello, eight years ago I dismantled an Okal prefab house in Frankfurt and rebuilt it in Spain. Since the stresses inside a house are not insignificant, I now want to do the following wall construction for my parents’ property, where I plan to move in later. I want to work with purely natural wood and aerated concrete.

The original wall construction was like in the Okal house, only beams of 9 cm (3.5 inches), which have now been replaced by 16 cm (6.3 inches); everything else has been removed from the wall.

My planned renovation

from inside to outside

12.5 mm (0.5 inch) gypsum fiberboard
19 mm (0.75 inch) tongue and groove boarding
Batten strips 3 x 5 cm (1.2 x 2 inches) or 4 x 6 cm (1.6 x 2.4 inches) with 3 or 4 cm (1.2 or 1.6 inches) width, with air space between
0.2 mm vapor retarder film (Delta Luxx Fabio)
Insulation: aerated concrete 350 kg/m³ (22 lb/ft³), with 8 x 16 cm (3 x 6 inches) squared timber spaced at 16 cm (6.3 inches) intervals
19 mm (0.75 inch) tongue and groove boarding
0.5 mm breathable membrane (Delta Vent S Plus)
Roof batten 24 x 48 mm (1 x 2 inches), with air space between
Offset tongue and groove boarding 19 mm (0.75 inch), or smooth-edged boards 19 mm (0.75 inch)

Thanks for the information.

see answer Fachwerk.de

My wall construction from inside to outside

22 mm OSB board, sealed at the joints with tape

8 x 16 cm (3 x 6 inches) squared timber as framework, whitewashed with the same material used for painting fruit trees

Between the timber studs: 155 mm (6 inches) aerated concrete

Then an 80 mm (3 inches) wood fiberboard

Finally, a lime plaster finish

There is no longer a horizontal beam at the bottom, but there is one at the top. I could remove the beams now and go with 200 mm (8 inches) wide aerated concrete, but I am concerned about the structural stability and the concrete blocks themselves.

I could also use 8 x 20 cm (3 x 8 inches) or 10 x 20 cm (4 x 8 inches); according to U Value Net, that would give a U-value of 0.231, which would be great—those beam dimensions are included in the calculation.

The house is not located in Spain but in Aachen. It is another house owned by my parents undergoing a complete renovation, as I intend to move in later.

The building has a full basement and a 1-meter (3 feet) clearance from the ground level. The concrete slab itself is 25 cm (10 inches) thick, and since it was poured incorrectly in 1972, there is no contact with the earth.

This wall setup naturally reduces interior space, but achieves an excellent U-value.

For heating, I plan to use individual wall-mounted air conditioning units with outdoor components in each room initially, as well as decentralized ventilation units per room, because later on I will install a wood log boiler with radiators.

Therefore, I am working without vapor barriers; the installations will be fixed directly onto the OSB board and consequently embedded in the aerated concrete.

OK??? I hope I am not making any fundamental mistakes.

see answer Fachwerk.de