The Majority of Homes in New Zealand Have Timber Frames
Homes in New Zealand are primarily built with timber frames. Because of this, any issues regarding changes to standards that affect the durability of the framing will have far reaching ramifications. Because this framing is largely concealed, any damage as evidenced in leaky homes is going to be hard to detect until it is at an advanced stage of decay.
Wood has been used as a primary structural material for many decades in New Zealand without any major problems. It is used as a structural material because of its high strength to weight ratio, it is easily worked and its cost compared to other structural options. The bad news is its susceptibility to rot, dimensional instability, size variability, pests, combustibility and vulnerability to the weather.
Wood Treatments Overcome Most Wood Disadvantages
Most of these disadvantages can be overcome by good design, and using the appropriate coatings and preservatives. This is particularly important when using a soft wood such as New Zealand grown Pinus Radiata for framing.
For almost 50 years we were world leaders in the production of the most durable wood. From the mid 90s until 2003, we decided that non-durable wood could be used (in the appropriate circumstances). Unfortunately this coincided with a time when building designs were harder to make waterproof and poor building practices were rife. With an ineffective regulatory system in place at the same time, we had a systematic breakdown of robust building practices and any effective regulations. These are the root causes for the unparalleled size of the leaky homes problem we now have.
Wood Rot in Leaky Homes
Fungi start to break down wood not long after the arrival of moisture as they start to change the properties of any untreated wood. Fungi are found everywhere and their microscopic spores permeate to all parts of buildings. Decay fungi grow within a few weeks, although significant wood damage usually takes several years. The damage is usually concealed and can often only be detected using specialist equipment.
Untreated Pinus Radiata was used in approximately 90 percent of structural framing in New Zealand between 1995 and 2003. When attacked by fungi, this untreated framing can lose the majority of its structural integrity within a few months, but typically in leaky homes this takes between one to three years.
Small Amounts of Leaking in Homes is Normal
Small amounts of leaking have probably been occurring in buildings in New Zealand for a century or more. Usually, these leaks didn't lead to wood decay or excessive mould because the older building designs allowed for drainage and drying. With the introduction of boron treated timber in the 1950s, combined with good design, this provided an adequate level of durability for many decades.
Because of the way buildings have been designed and built between 1995 and 2003, leaks were a far more serious problem because of the size of the leaks, and because the buildings weren't built to handle them properly if they did leak.
The primary problem with leaky homes therefore is the weather tightness of the structure.
The secondary problem is the durability of the framework that makes up the leaky homes.
Wood Borer Pest and Leaky Homes
Wood borer attacks untreated Pinus Radiata when the moisture level is above 5%, and thrive when it is over 7%. Chemical free framing timber used in the majority of leaky homes was kiln dried to a moisture level of 4% to prevent borer eating it, and at a high enough temperature to kill off anything already living in the timber. Once the timber is used in a building, over a period of time it absorbs more moisture, or looses moisture based on the moisture levels of its surroundings. For example in a hot water cupboard, the wood is usually far too dry to be attacked by borer. Areas such as bathrooms, laundries, kitchens, and shady dark rooms in dampish areas can have moisture levels up to 11% or more, especially if the building is leaking. Untreated doors, window surrounds, skirting boards, shelving and door frames will also get attacked by borer.
All is not lost. Timber can be treated where it is accessible with Boric (Disodium Octaborate Tetrahydrate). This will not only help in the prevention of borer infestations in the wood, it will also help prevent, or kill off rot. There are also new products on the market which are specifically aimed at stopping rot.
Homes in New Zealand are primarily built with timber frames. Because of this, any issues regarding changes to standards that affect the durability of the framing will have far reaching ramifications. Because this framing is largely concealed, any damage as evidenced in leaky homes is going to be hard to detect until it is at an advanced stage of decay.
Wood has been used as a primary structural material for many decades in New Zealand without any major problems. It is used as a structural material because of its high strength to weight ratio, it is easily worked and its cost compared to other structural options. The bad news is its susceptibility to rot, dimensional instability, size variability, pests, combustibility and vulnerability to the weather.
Wood Treatments Overcome Most Wood Disadvantages
Most of these disadvantages can be overcome by good design, and using the appropriate coatings and preservatives. This is particularly important when using a soft wood such as New Zealand grown Pinus Radiata for framing.
For almost 50 years we were world leaders in the production of the most durable wood. From the mid 90s until 2003, we decided that non-durable wood could be used (in the appropriate circumstances). Unfortunately this coincided with a time when building designs were harder to make waterproof and poor building practices were rife. With an ineffective regulatory system in place at the same time, we had a systematic breakdown of robust building practices and any effective regulations. These are the root causes for the unparalleled size of the leaky homes problem we now have.
Wood Rot in Leaky Homes
Fungi start to break down wood not long after the arrival of moisture as they start to change the properties of any untreated wood. Fungi are found everywhere and their microscopic spores permeate to all parts of buildings. Decay fungi grow within a few weeks, although significant wood damage usually takes several years. The damage is usually concealed and can often only be detected using specialist equipment.
Untreated Pinus Radiata was used in approximately 90 percent of structural framing in New Zealand between 1995 and 2003. When attacked by fungi, this untreated framing can lose the majority of its structural integrity within a few months, but typically in leaky homes this takes between one to three years.
Small Amounts of Leaking in Homes is Normal
Small amounts of leaking have probably been occurring in buildings in New Zealand for a century or more. Usually, these leaks didn't lead to wood decay or excessive mould because the older building designs allowed for drainage and drying. With the introduction of boron treated timber in the 1950s, combined with good design, this provided an adequate level of durability for many decades.
Because of the way buildings have been designed and built between 1995 and 2003, leaks were a far more serious problem because of the size of the leaks, and because the buildings weren't built to handle them properly if they did leak.
The primary problem with leaky homes therefore is the weather tightness of the structure.
The secondary problem is the durability of the framework that makes up the leaky homes.
Wood Borer Pest and Leaky Homes
Wood borer attacks untreated Pinus Radiata when the moisture level is above 5%, and thrive when it is over 7%. Chemical free framing timber used in the majority of leaky homes was kiln dried to a moisture level of 4% to prevent borer eating it, and at a high enough temperature to kill off anything already living in the timber. Once the timber is used in a building, over a period of time it absorbs more moisture, or looses moisture based on the moisture levels of its surroundings. For example in a hot water cupboard, the wood is usually far too dry to be attacked by borer. Areas such as bathrooms, laundries, kitchens, and shady dark rooms in dampish areas can have moisture levels up to 11% or more, especially if the building is leaking. Untreated doors, window surrounds, skirting boards, shelving and door frames will also get attacked by borer.
All is not lost. Timber can be treated where it is accessible with Boric (Disodium Octaborate Tetrahydrate). This will not only help in the prevention of borer infestations in the wood, it will also help prevent, or kill off rot. There are also new products on the market which are specifically aimed at stopping rot.
Posted in: Home Inspections
