The standard stud height of rooms in 1970s houses was 2.4 m, but additional height was often achieved in living spaces by a sloping ceiling that followed the line of the roof.
A range of wall and ceiling linings were used in the 1970s. The most typical were plasterboard, softboard, and - in service areas - hardboard. TG&V timber was also used for feature walls and sloping ceilings, and a range of other materials was also available though less commonly used.
Typically, living and sleeping area walls were lined with paper-faced plasterboard.
Service and wet area walls were typically lined with hardboard sheets.
TG&V timber boarding (typically rimu) was occasionally used for feature walls in living areas.
Other lining materials that were available but less commonly used included plywood, particleboard or MDF sheets, proprietary factory applied vinyl to plasterboard (though this was more common in commercial work), and prefabricated internal wall systems.
Softboard, though generally used only as a ceiling lining, is occasionally found as a wall lining.
Some houses had a plastic or other vapour barrier installed between the lining and the external wall framing. Rarely, a vapour barrier was also installed in ceilings. A specific vapour barrier was not required in most domestic buildings in New Zealand at the time.
Plasterboard walls in living areas and bedrooms were generally wallpapered. The patterns were bold and colourful.
Service areas and ceilings were typically painted, or, where timber based products were used, clear finished (Figure 1). Paint finish to walls in living areas was starting to become more popular as the decade ended.
TG&V timber boards or plywood sheets were typically clear finished.
Ceilings were most often softboard tiles or sheets, though flush-stopped plasterboard was also reasonably common, as was hardboard in service and wet areas.
Other lining materials that were available but less commonly used included fibrous plaster, plywood, particleboard or MDF sheets, and woodwool slabs.
Sloping ceilings sometimes had concealed rafters and were lined with plasterboard, and sometimes had exposed timber rafters in which case the lining might be plasterboard, rimu TG&V, or another material.
With sloping ceilings, a ridge beam was commonly used instead of a ridge board to support the rafters and to eliminate the need for collar ties or cleats.
Scotias were typically a small, concave plasterboard moulding. Sometimes plasterboard was used and, from 1976, MDF. A timber bead with a bevelled edge was used for sloping ceilings.
Plasterboard ceilings were typically painted or may have had a sprayed, textured finish applied over a sheet lining material. A number of textured finishes applied to ceilings during the 1970s contained asbestos fibres. Any such finishes remaining are likely to be nearing the end of their life (they tend to become crumbly) and are likely to need removal by a specialist contractor.
TG&V timber board or plywood sheet ceilings were typically clear finished.
Paper-faced plasterboard sheets were easy to install and the surface could be stopped to create a smooth, flush finish to which wallpaper could be applied directly. Later in the period, paint finishes became more common.
Plasterboard was 9.5 mm or 12.5 mm thick and available in 900 or 1200 mm wide x 1.8-3.0 m long sheets.
Plasterboard was usually nail fixed although adhesives were available. Sheets were nailed at 100-125 mm centres with galvanised flat-head clouts, 12 mm from the sheet edge.
Nail holes and joints between sheets were stopped with plaster and trowelled to a smooth finish. Tapered edges to plasterboard had become available during the 1960s, making it easier to achieve a flush finish to the stopping.
The introduction of NZS 3604 in 1978 allowed the use of sheet material such as plywood and plasterboard as internal bracing to resist wind and earthquake loads. Initially the fixing down of the wall bracing panels to the floor was not specified.
Using the generic bracing ratings that were assigned to these materials by NZS 3604 could help in determining the level of bracing provided in the original construction.
During the 1970s, foil-backed plasterboard was marketed as a lining material that also provided insulation and a degree of moisture vapour resistance, but the increase in insulation value of an external wall was minimal.
Fibrous plaster was sometimes used to line ceilings of more expensive housing because of the quality of finish that could be achieved. Fixing and finishing were similar to plasterboard, but the stopping was steel trowelled and polished to finish the joints.
Softboard tiles were interlocking, around 400 x 800 mm and 12 mm thick, and had a prefinished exposed surface. Tiles were fixed to 40 mm thick timber battens and were commonly used for ceilings in all areas of the house. Softboard sheets were manufactured with a chamfered edge to form an expressed vee joint when close butted.
Hardboard is a low-cost compressed wood fibre sheet material. Painted oil-tempered sheets, with improved moisture resistance when compared to standard sheets, were suitable for use as a wet area wall and ceiling lining for kitchens, bathrooms and laundries.
Hardboard was also the substrate for pre-finished wallboards suitable for use as a shower lining or bath surround such as Formica, which had a plastic laminate coating, or Seratone and Riotone, which were a melamine finished patterned wallboard. Factory formed decorative finishes to standard hardboard included leathergrain, timber grain, tiled pattern, peg board and flat sheets with a timber veneer finish.
Sheets sizes were typically 2.4 m x 1.2 m and thicknesses of 3, 4.5 and, most commonly, 6 mm.
Joints could be butted with a small arris to create a rounded or veed edge, with aluminium or plastic mouldings or with half-round timber beads. In showers and wet areas the edge jointer was used.
Plywood was used in a smaller number of houses as an internal wall and ceiling lining.
Typically it was used with butted expressed joints, but joints could be arrised, veed, or covered with timber beads or battens.
Sheets were generally 1200 x 2400 mm and available in thicknesses of 6, 7.5, 9 and 12.5 mm.
Fixing was by gluing or nailing to timber framing, with panel pins lightly punched below the surface at approximately 100 mm centres around edges and 225 mm centres across the middle.
Sheets could be clear-finished, stained or painted.
As noted in plasterboard above, the introduction of NZS 3604 in 1978 allowed plywood to be used as internal bracing. Sheets of 6 mm or 7.5 mm thickness were sometimes also fixed to the outside of the framing as bracing.
Timber panelling (TG&V) was sometimes used as a feature wall or for a sloping ceiling, generally in the living room. However, most often use was limited to interior trims such as skirting. An adequate supply of rimu was still available, although it tended to be sap rather than heart.
Natural timber was generally stained and/or polyurethaned.
Fireplace surrounds for open fires could be clad full-height with stone or brick. A similar finish was sometimes continued on the exterior.