Suspended floors: original details

1970s houses typically had particleboard flooring finished with carpet, vinyl or tiles. But T&G timber was also used.

Flooring during this period was predominantly particleboard sheets. However, some rimu and matai T&G flooring was used in higher cost or architecturally-designed housing. Rimu and matai were more often used in South Island houses.

Later in the 1970s, there was a significant increase in the use of in-ground concrete slabs.

From later in the 1970s, perforated foil insulation was used draped over the floor joists before the flooring was laid (Figure 1). Original foil remaining is likely to be in poor condition and will not be providing effective insulation.


Particleboard flooring

High density (HD) particleboard flooring was first used in the 1960s and quickly became popular during the 1970s. MDF flooring became available in the late 1970s.

As sheet flooring was laid over the entire floor before wall framing was erected, it provided an immediate work platform and a flat level surface on which to construct wall frames.

It was available in 2440 x 1220 x 20 mm and 3660 x 1840 x 20 sheets initially, then, as manufacturing changed to metric, in 2400 x 1200 x 20 mm and 3600 x 1800 x 20 mm sheets.

Fixing was by nailing, and timber blocking was required between joists to provide support and fixing for panel edges. Nails were punched and the floor could be sanded and finished in the same way as timber floorboards.

Once particleboard flooring was installed, the building was meant to be closed-in quickly (although this did not always occur) as particleboard and MDF were not designed to withstand sustained wetting.

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Timber strip flooring

Timber strip flooring was machined from 150 or 125 mm boards (finished thickness 19.8 mm).

Floor boards were laid after external and internal load-bearing wall framing was erected and the building was weathertight (to protect the expensive timber from water damage).

One exterior wall of the building was usually used as the starting point to provide a solid edge against which to cramp boards before they were double-nailed to the joists to secure them. Alternatively, board laying was sometimes started in the middle of the building (depending on the layout of the rooms) after fixing nails were punch and the floor sanded.

Secret nailing, using a different board profile with a stronger tongue, was sometimes used if it was desirable that nailing was not visible.

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Floor finishes

Particleboard was often stained or clear-finished as a cost saving measure, but it was usual for it to be overlaid with carpet, vinyl or cork tiles. The 1970s also saw the common use of clay quarry tiles on kitchen and entry floors, particularly in architect designs and upmarket construction.

Timber floors, because they had a more attractive appearance, were clear finished.