A wide range of issues affecting design and structure will need to be considered as part of any 1940s-60s renovation.
The houses of this period typically had a generous roof slope and eaves to shed water, good ground clearance – often over 24” (600 mm) – for subfloor ventilation, and were initially built using quality heart timbers. Houses of this period were generally of sound construction and are less likely to have significant external moisture problems.
The introduction of new materials and methods of construction, particularly during the 1960s, as well as changes in design and layout, meant there was experimentation and a higher risk of moisture ingress, and a lack of durability of some of the materials which means that some of these houses may not have performed as well as expected.
As houses predominantly had timber joinery they were relatively air leaky compared to a modern house with aluminium joinery. They were generally less susceptible to internal moisture problems such as condensation and mould but they are colder due to the draughtiness and lack of insulation.
Before undertaking any renovation or remedial work to address issues such as inadequate layout, space, indoor/outdoor flow or replacement of outdated fixtures, the condition of the existing building should be carefully reviewed. There are a number of aspects of the building that should be considered, evaluated and (possibly) addressed as part of any renovation project. These include:
The original design and layout and subsequent unsympathetic or poorly carried out alterations may need to be addressed to rectify issues such as:
- a desire for better indoor/outdoor flow
- arrangement of rooms to benefit from passive solar heating
- lack of a variety of living spaces that are associated with more modern houses
- lower natural indoor light levels
- poor relationships between spaces – for example, proximity of bathroom and bedrooms
- inadequate services such as insufficient power outlets
- lack of vehicle access and/or garaging.
Any new extension may involve consideration of compliance with current Resource Management Act constraints for side yards and site coverage.
Structural problems in 1940s-60s houses may include undersized framing, inadequate bracing, and unsafe chimneys. Read more.
Houses built during the 1940s-60s generally have few weathertightness issues. With renovation, attention will be needed to ventilation to ensure that internal moisture does not become a problem. Read more.
Matching new to existing
With any 1940s-60s house renovation, there will be areas – such as framing sizes, mouldings, and roof profiles – where original features need to be replaced or new construction must merge with existing. Read more.
Few houses built in the 1940s and 1950s were insulated. Insulation may be required as part of any renovation project, and in any case will provide benefits for occupants. Read more.
Original copper pipes will probably not need replacement but plastic pipes installed during renovations in the 1970s or early 1980s may. Read more.
Low pressure hot water systems may need to be upgraded to mains pressure. Pipes may need replacement to cope with the higher pressure. Read more.
Some 1940s-60s houses will still have black rubber-sheathed cabling (called TRS or tough rubber sheath). The sheathing of TRS cabling deteriorates over time so any remaining original cabling should be replaced. Read more.
Foundations and subfloors
Most foundations will be in good condition aside from lacking earthquake bracing. Other common problems include unevenness and corrosion of reinforcing. Some houses will have problems with subfloor moisture. Read more.
Original roofs will need maintenance and may need replacement. Read more.
Internal walls and ceilings
Problems may include walls that are out of plumb or are unsuitable for paint finish, and linings that have cracked due to building movement. Read more.
Original windows are unlikely to be double-glazed and may not be airtight. Original frames may be in poor condition. Read more.
Metal elements such as roofing, fixings and flashings may have corroded and need replacement. Corrosion can affect structural performance. Read more.
Borer, rot and mould
- Borer may be found in 1940s-60s homes native timbers and untreated pine, particularly if they have become damp. It is unsightly and can sometimes affect a house’s structure.
- Mould is common when moisture levels have been high, the subfloor is damp, ventilation has been poor or there has been a leak. It may initially be seen on painted and papered walls and ceilings, and on fabrics. Mould can be harmful to health.
- Rot is common when moisture is present, and can cause significant structural damage.
See Borer, rot and mould for details of how to identify and respond to these problems.
Health risks: asbestos
Asbestos-cement was used in 1940s and 50s for wall and roof claddings and also in 1960s floor coverings and spray textured ceilings. It becomes a health hazard when old materials containing asbestos are being removed or break down, allowing the fine particles to become airborne and breathed in.
Health risks: lead
Lead was used in house construction in the 1940s-60s in external and internal paintwork, flashings, valley gutters and nail heads. Serious health problems can result if materials containing lead are swallowed or inhaled.
Oil-based paints containing lead were commonly used until the mid-1960s when the health hazards became more fully understood. The use of white lead in paint was banned in 1979 but some special-purpose paints still contain red lead. It is not possible to identify lead-based paint from its appearance. If a building is over 25 years old, assume that it has been painted with lead-based paint.
See lead for information on dealing with lead contaminants.
Health risks: treated timber
Timber treatments can be hazardous to health, so care must be taken when working with treated timbers. Boric treated timber may be found in houses built during this period. CCA-treated timber is unlikely to be found in houses built in the 1940s and 1950s, though it may be found in exterior situations such as fences. Read more.
Fire safety was not generally a consideration for the design and construction of houses built in the 1940s-60s. Although plasterboard linings reduced the risk of fire spread, furnishings as well as dry timber present a significant fire load. Read more.