Important professional note: This is an archival educational text, not a current design, calculation or instruction for waterproofing, thermal protection or acoustic insulation. The wall solution must be checked for the specific structure, soil, water, climate, fire, moisture, condensation, acoustics and materials according to applicable regulations, standards and manufacturer documentation. Historically mentioned products and methods, including lead sheets, do not constitute a recommendation for use today.
The design and construction of walls and insulation is not part of the current public offer of Savo Kusić. Today’s production focus consists of wooden windows, wood-aluminum windows and custom doors.
1. Modular dimensions and types of walls
With regard to modular dimensions in building construction, a distinction is made between walls with joints (brick walls) and walls without joints (concrete walls). The lengths and thicknesses of jointless structural systems, as well as the widths and heights of window and door openings, correspond to building coordination dimensions.
For structural systems with joints, the joint width is subtracted from the coordination dimensions for wall length and thickness to obtain the nominal dimension. For example, if the wall length according to the coordination dimension is 10 m, the nominal value – i.e. the actual length – will be 9,99 m (the width of one joint is 1 cm).
For openings (and clear internal dimensions) in systems with joints, one joint width should be added to the coordination dimensions to obtain the nominal dimension. For example, if the clear width of an unfinished masonry window opening is 1,5 m as a coordination dimension, the nominal width will be 1,51 m. Since the thickness of the adjoining joints in brick walls is usually 1,2 cm, this dimension is added to the opening height.
Walls can be classified into several categories:
- Constructive wall systems:
- Layered walls - only for heritage and retaining walls
- Cast and rammed walls
- Walls laid in mortar
- Slab walls
- Walls for filling skeletal constructions
- Frame-shaped walls
- Walls made of prefabricated panels
- Walls made from composite systems
- Types of walls according to purpose:
- Foundation walls
- Basement walls
- Exterior walls of buildings
- Interior walls of buildings
- Attic walls
- Types of walls according to material:
- Natural stone walls
- Concrete walls
- Brick/block walls
- Glass walls
- Steel walls
- Wooden walls
2. Protection of walls from moisture
In the case of basement wall protection, there is protection against underground water and protection against underground moisture. Protection from underground water means that the level of underground water is below the level of the basement floor. If the underground water level is above the level of the basement floor, we are talking about protection from underground water. The performance for these two levels of protection is very different, as much more protection is required from groundwater than from moisture.
Protection from ground moisture is executed differently for horizontal and vertical layers. A horizontal layer is made from waterproofing felt, while a vertical layer uses bitumen- or synthetic-asphalt-based materials. Cement screeds can sometimes also be applied.
For protection against groundwater, a bitumen- or synthetic-asphalt-based waterproofing membrane is used. Insulation made of jute or lead sheets is also mentioned.
Exterior walls that are not built of natural stone or facing brick, or are not clad with ceramic tiles, glass plates or light-metal sheets, can be protected from driving rain and other atmospheric moisture by applying impermeable render (with added insulating materials), colourless sealing coatings or other methods.
3. Thermal insulation of walls
For rooms occupied permanently, minimum thermal protection is sufficient to maintain favourable health conditions; it represents the lower limit of thermal protection at which water-vapour condensation on the internal surfaces of external walls is prevented. This “minimum thermal protection” does not address the economic aspect of heating. Improved – and more economical – thermal protection, which can be determined by calculation, is needed for that purpose.
Thermal insulation of external walls that is found to be suitable and especially economical must be continuous across all wall surfaces, including window niches, lintels, reveals and window openings, ring beams, etc., as well as the vertical walls of the built attic and those parts that enclose the heated space towards the roof covering or lower rooms.
Walls with an internal insulating lining have an advantage over other types of insulation for health reasons, due to their lower overall heat-storage capacity and reduced removal of heat radiated by the human body.
It is very important to insulate radiator niches and water pipes in external walls thoroughly. It is often useful to cover the wall surface behind a radiator with aluminium sheets so that thermal radiation directed towards the external wall is reflected back into the room.
4. Sound insulation of walls
There is insulation against airborne sound, which is transmitted through the air, and insulation against impact sound, which is transmitted through the structure.
Airborne-sound insulation of 48 dB can be considered minimum protection even for partition walls in important offices. It is better if the sound insulation is increased to 50 dB, whereby the ordinates of the limit curve for walls are raised by 2 dB.
Solid walls transmit sound exclusively through flexural vibration. Incident sound causes the wall to vibrate, which in turn causes the air on the side opposite the sound source to vibrate. On this basis, acoustic-insulation practice distinguishes between single-leaf and multi-leaf walls.
In acoustic-insulation practice, single-leaf walls include walls built from one or more rigidly connected leaves. Individual leaves can be made from different materials. The sound-insulation coefficient of single-leaf walls depends on mass (weight per square metre), flexural rigidity (more precisely, the ratio between flexural rigidity and mass) and air permeability (uncracked, properly coated walls). For minimum acoustic protection of 48 dB, the minimum weight of a single-leaf wall must be 350 kg/m2, and for 50 dB about 480 kg/m2.
The composition of the mortar and coating significantly affects the sound insulation of walls. A coated wall always provides better sound insulation than an uncoated one because the coating seals the wall surface more effectively. This improvement is achieved even when the coating is applied to only one side of the wall. For walls made of porous material, the coating is very important acoustically because it prevents sound transmission through the pores.
From an acoustic perspective, multi-leaf walls consist of two or more wall leaves with no rigid connection between them, separated by an air layer. Only where a flexible, heavier leaf is placed in front of a solid wall 10 cm thick or more can such wall leaves be connected without particular harm to the sound insulation, for example by a widely spaced batten frame. The greater the space between the two leaves, the better the insulation (provided, of course, that insulation by the cavity is sufficient).
The following proved to be particularly useful:
- two leaves made from lightweight wood-wool boards, installed free-standing at a minimum distance of 3-5 cm from each other; total wall weight about 90 kg/m2,
- two completely separate timber frames, clad externally with lightweight wood-wool boards with a minimum thickness of 3,5 cm.
Double light walls of mutually separated rigid shells of equal weight are not suitable.
The sound insulation of a certain wall will be successful only if there are no openings in it, because in that case the sound will transmit directly through those openings. Small openings that are equal in scale to the wavelength of a sound, or smaller than it, will act on the adjacent room as a new source of sound.
Application note: Historical dimensions, masses, acoustic-protection values and descriptions of insulation layers are not a substitute for current building-physics calculations, connection details, control of thermal bridges, moisture and airtightness, or measurement of the as-built condition.