Borer and your home

As a professional building inspection company, one aspect of our inspection process involves identifying any evidence or risk of pest infestation. While this can range from rodents to insects, one of the most common in New Zealand homes is borer.

Homes located in the cooler areas of New Zealand, such as Southland and Otago, are more likely to be affected by borer, however no area of the country is immune. In fact in Wellington, borer is one of the main reasons buildings have become ‘at-risk’ in an earthquake because the infestations have compromised the foundations and structural integrity. 


What is Borer?

Borer are small brown beetles whose larvae spend 2- 4 years eating their way through soft timbers such floorboards, timber house piles, weatherboards, door and window frames, joists and timber furniture, before emerging through small flight holes.

New Zealand has two types of borer - the most common being the Common House Borer and the rarer but more concerning, Two-Tooth Long-Horn Borer.

The easiest way to identify which type of borer is affecting the timber in your home is to look at these holes: the Common House Borer leaves a small round hole, while the Two-Tooth Long-Horn Borer leaves an oval hole up to 5 mm long.

Borer beetles


Identifying Borer:

Borer do not damage timbers as fast as termites so the increase in flight holes can often be missed or ignored for years. Each year the floor boards may creak a little more, the timber joinery might take a little longer to fill before painting, but until you fall through a floorboard or notice rot in the joinery and weatherboards from water entering the flight holes, you may not even be aware your home is in danger.

The majority of these holes will be found in dark and humid areas such as inside the walls, roof space, or under the floor, so be aware that what may appear to be a ‘minor’ infestation on the accessible surfaces in the home, could be a sign of a bigger problem beneath.   

borer in floorboardsborer in floorboards

As the south side of a dwelling is usually the coolest and dampest, this is the best place to start when checking for signs of borer.


Can Borer really compromise the structure of my home?

Infestation by the Common House Borer generally tends to cease before the timber becomes structurally compromised. This is because the borer only attack the sapwood in the timber (Softwood) and there is generally sufficient heartwood in framing timbers to avoid serious weakening.

However infestation by the Two-Tooth Borer is far more serious because they can attack the heartwood timber as well, and structural failure can sometimes occur before their presence has even become evident. 

Borer eats through joist

How to treat Borer?

For all homes, but especially those pre-dating the 1960’s it is recommended a precautionary approach is taken and that you treat you home regularly for Borer. There are a range of products on the market which will kill larvae and prevent re-infestation for years to come.

Where Borer has been identified in structural timber such as joists or rafters, the difficult decision is determining the extent of the damage. If the Common House Borer is present the timber can often be left or strengthened, however if the Two-Tooth Borer is present the timber should be replaced.


For an inspection of you home for the presence of borer, call us today on 0800 487 884



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