An unusual and unwanted guest in a recently laid oak flooring. If the supplier's initial response was correct, and it really was woodworm, the client would have had to shoulder the costs of a new floor. 

Now here's one you don't often see!  These clients had an oak planked floor installed a year or so before they noticed a problem.  The problem was in the guise of 2-4mm holes 'appearing' at the surface of the wood.

The company they bought the flooring from were sympathetic but thought it was probably 'woodworm' and as such was the client's responsibility.

A closer look revealed the true nature of the beast - it was a beetle of the Ambrosia spp or, to give it its common name, Pin Hole Borer.  As such the timber wasn't fit for purpose and, if they decide to change it, it's down to the supplier.

It pays to get your own survey!

Property Huddersfield

Instructions To inspect the ground floor of the property and comment on apparent beetle emergence holes in a recently laid oak planked floor.

Background The clients recently purchased, and laid, a decorative oak floor; this was carried out approximately twelve months ago. Around May of this year the clients began to notice small holes appearing randomly in the surface of the boards. It is their opinion that this situation is deteriorating and that more holes have appeared recently.

Upon approaching the suppliers, Messrs xxx, they were informed that this was probably woodworm and that it must have originated after the floor was purchased. They cite their policy of kiln drying the timber prior to sale as evidence of this.

If this (woodworm infestation) were the case, the floor would probably require lifting and re-laying with sanitised timber and the consequent expense would be formidable. Prior to taking this decision the clients require an opinion on the cause of the distress.

Disclosures I am not aware of any affiliation, financial or otherwise, with the client or the property.

Limitations Limited to the instructions.

Restrictions The floor was not lifted but unused timbers were inspected.

Date of Survey September: 2006

Weather: Heavy rain

Viewing Orientation: Unless otherwise stated, all observations are made as if looking towards the house from the front.

Type of Property: Modern, two-storey house with sealed unit double-glazing and gas central heating.

External Observations: N/A

Internal Observations:

These observations are limited to the flooring in the dining room and entrance hall, which have a solid oak, plank overlay with a protective/decorative finish. The dimension of the planks are approximately 160mm x 22mm and they have a PTG profile.

Close inspection revealed several areas where holes with diameters of between 2 and 4mm were visible. As mentioned previously, these holes were randomly scattered around the boards; they were apparent in some and not in others.

A paperclip was inserted into some of the holes and it penetrated easily to a depth equivalent to the thickness of the boards. There was no frass.

The clients had spare boards that have not yet been laid and these too were examined. Holes were also visible in these and, on the underside of one of them, two grooves, inserted by the suppliers, have been cut into the surface with a spindle-moulding machine. Where this groove intersected with the holes, their (holes) profile was elongated, thus showing the moulding was carried out after the holes were made.

I sectioned one piece of timber and it is possible to see that the holes progress into the timber to a considerable depth and small galleries have been formed internally. The surface of the galleries is darkened by a fungal growth, which is undoubtedly the result of ambrosial fluid deposited by a species of Ambrosia, or pinhole beetle.

Discussion:

Although I have little doubt that the holes in the timber are caused by a beetle of the Ambrosia spp.; I do not know which particular one.

This species of beetle attacks distressed or newly felled timber and is essentially a forest insect. It will therefore have been resident prior to the timber's processing into planks.

The elongation of the galleries caused by the spindle-moulder illustrates this perfectly and the darkened sides of the gallery walls confirm the diagnosis.

Unlike woodworm, the ambrosia beetle itself causes the damage to the timber as it bores into it in the first place (with most other wood boring insects the grubs cause the damage).

It bores holes and constructs galleries where its offspring can grow, pupate and eventually emerge as adults. In order to provide food for them during this process, it deposits fluid on the walls of the tunnels as it bores. This fluid encourages fungal growth, upon which the grubs then feed.

There is thus no reason for the grubs to eat the timber itself and the damage they cause is negligible; they emerge from holes already created by the adult. The process is then repeated but only in timber with a fibre moisture content that is at saturation level, i.e. approximately 35% moisture content.

I am surprised that these holes were not noticed prior to the sale; or at least, prior to laying the floor. The only conclusion I can reach is that the decorative/protective surface coating, together with sawdust from the processing, filled the holes and thus made them difficult to see. Ongoing cleaning, vibration and general use has caused the sawdust to fall out and the surface coating of the lacquer finish has now broken; thus they (holes) are becoming evident.

Given the above, I do not expect that any more holes will appear, although I cannot be entirely sure of this. If they do, the timber may eventually become too damaged to keep, but I cannot be the arbiter of that; you may feel it is in keeping with the (intentional) distressed effects of the flooring.

Conclusions:

The distress to the timber is caused by a beetle of the Ambrosia spp.

This timber must have been infected prior to its purchase and subsequent installation by yourselves. It cannot have occurred after the timber had been seasoned and most probably happened when the timber was still in log form.

I do not think the damage will worsen but I cannot be sure; you should observe the timber over the next year or so.

No chemical treatment is necessary.

I trust the above is satisfactory for your purposes but if you require further clarification please do not hesitate to contact me.

Surveyor Patrick F Doyle CSRT M. Inst. R.T.S.

Qualifications Certificated Surveyor in Remedial Treatments issued by the BWPDA.

Date of Report September 2006

Signed Surveyor