Ultrasound scanner for assessing woodworm damage

[hgreaves]

Hi all

We are hoping to buy a cottage in Oxford that has lots of internal structural timbering. There are signs of woodworm but it is not clear how much damage this has done to the beams. We have been told that the only way to really detect e.g. whether the inside of the beam is hollow is by means of a handheld ultrasound scanner. I think that these are prohibitively expensive to buy. Does anyone know whether it is possible to pay someone with a scanner to come and look at this (better still, anywhere we can hire/borrow a scanner)? We have tried asking a few surveyors but they all say don't have/use ultrasound scanners.

Thanks in advance for any replies!
Hilary Greaves.

 

[Penners]

Hello Hilary

Before you start resorting to the cutting edge of expensive science, just how much evidence is there of woodworm activity? How old is the cottage and how much of it is timbered?

Have you had a structural survey done? If so, what did the surveyor have to say about the evidence of woodworm - either active or inactive?

Sorry - you wanted answers rather than questions, but the above additional information will help the forum's knowledgeable people on this subject to give you better-informed answers.

 

[FamilyWiggs]

Hello Hilary - welcome to the forum.

Woodworm can be worrying, but in my (limited, non-expert) experience, it usually less of an issue than people first think. Woodworm like moist timber which usually means the outer sapwood or damp timbers. Quite extensive surface evidence can be on top of a beam which is is strong as concrete underneath.

I've never heard of using an ultrasound scanner - but I doubt that the attack could be so extensive as to hollow out the core of a beam, without there being external evidence of structural collapse. Again, in my limited experience, the attack is generally the outside layers of the timber. If possible, a cheaper alternative might be to take a fine core from part of the timber to examine? Spraying expensive and toxic chemicals around only satisfies mortgage companies, and is generally considered on the forum as a relative waste of time and money.

A good surveyor who understands period properties should be able to advise you properly. Not one linked to toxic chemical companies or modern Barrat boxes though.

As Penners says, try to see if the attack is active (look for frass or put tissue paper over the flight holes to look for evidence of exiting beasties).

Proper experts will be along shortly, no doubt.

 

[Flyfisher]

A survey by someone thoroughly familiar with period properties sounds as if it would be money well spent - if only for peace of mind.

Our house has ample evidence of woodworm activity but it's also full of beams so tough that it's impossible to drive a nail into them. I'm sure the timber frame is not as strong as it was when first built but as it was clearly substantially over-engineered in the first place, it doesn't really matter very much.

Out of interest, is there anyone here living in an old house where there are NO signs of woodworm?

 

[Feltwell]

Out of interest, is there anyone here living in an old house where there are NO signs of woodworm?

Quite - I've yet to come across a house built before 1930 that doesn't have signs of woodworm somewhere!

 

[hgreaves]

Hi all

Thanks for the replies! First to answer Penners' questions:

The older part of the cottage is reported to be 17th century, the newer extension 19th century. There are numerous ceiling beams in all the downstairs rooms, plus some uprights in the older downstairs rooms, one exposed structural ceiling beam in one of the upstairs rooms, and a few lintels over windows. (In case it helps more than my verbal descriptions, there are photos on the rightmove brochure at http://www.rightmove.co.uk/property-for-sale/property-26775103.html .)

Many of the beams have numerous woodworm holes, but we don't know whether or not it is active. In many cases the fact that the beams are painted makes it more difficult to see what is going on.

We have not had a surveyor look at the property, as the more frank of the surveyors we talked to (as well as friends who have employed surveyors in the past) commented that there was nothing they could do that we couldn't look at ourselves with a bit of time and common sense. Hence we have so far been taking the DIY approach to surveying. I gather that many on here have a more positive view of the usefulness of the better surveyors though!

I now have some more questions in response to the other comments:

Please could someone explain in more detail how the tissue paper test works - how long do you need to put the tissue paper there for, does it matter how it is fixed to the beam (how tightly etc), and what exactly does one expect to see if the woodworm is active (i.e. are there any ways this test can be done incorrectly/misinterpreted, or is it common sense)?

The vendor commented that she thought the woodworm had been treated in the past (but before she bought the house, so more than 10 years ago). I had been under the vague impression that treating woodworm was important, but have not had any call to investigate before. Is it this standard sort of woodworm treatment that forum users generally regard as useless? What *is* regarded as a sensible reaction to discovering woodworm? (E.g. don't worry about it and eventually replace bits of timbering as necessary? I gather from the last two comments that it isn't something you tend to worry about too much...)

Thanks again for the help!
Hilary

 

[Flyfisher]

Hi Hilary,
The idea of tissue paper is to fix it over suspected areas of timber to reveal where the beetles emerge to fly off somewhere else. I'm no expert on this but my understanding is that this typically occurs during springtime, so I doubt it's very helpful for a prospective buyer, more for an existing owner who wishes to monitor things over a period of time.

"Frass" is dust-like traces of wood that can fall from wood with active infestation. Again, it's hard to see how this would be noticeable by a prospective buyer, especially if the vendors are keeping the house clean and tidy during the selling process, but it's a useful indicator for owners who can monitor such things over time.

But, from what I've read (including from our resident professional expert), woodworm requires a certain level of moisture in the wood. So, a heated house with a well ventilated attic and, if appropriate, floor voids, together with breathable materials around any 'buried beams' is very unlikely to suffer from active infestations.

Your surveyor advice also seems fairly sound. In my experience, the standard sort of 'mortgage survey' only involves a walk around the property looking for anything obvious that might affect the value of the property (remember that mortgage companies are only really interested in securing their loan) and as you've been advised, that's something that you can do fairly easily. A 'full structural' survey by a suitably-qualified person with period property experience will give a lot more detail but will also be quite expensive and you should discuss, and specify, your requirements from the survey before commissioning such a survey.

Whatever you decide, there is always a leap of faith when it comes to period properties and a lot depends on your attitude to such a property. We've discussed here before that there is an element of 'living with' such properties rather than judging them with 21st century new-build expectations. The good news is that their very existence after a few hundred years is an indication of being fairly well-built in the first place and, for what it's worth, the house in question looks well-looked after.

Finally, woodworm can certainly be dealt with in a variety of ways (including just not worrying about it :wink: ) but I'm afraid that we're not really anywhere nearer knowing if there is actually a woodworm problem with the property in question. Some holes in some beams is certainly no proof of an active infestation, only of previous activity - which may well have ceased hundreds of years ago.

 

[MdB]

If the wood has been painted recently, new woodworm holes can be spotted as they look like somebody has used a small drill to make a new hole through the wood / paint. The edge of the paint will be visible as will newly eaten wood.

An old hole that has been painted over will look very different with the paint going into the hole a bit.

 

[hgreaves]

Hi Flyfisher,

OK - thanks for the comments!

Re. surveys, it was actually the full structural survey I was talking about... unfortunately we do have to pay good money for the valuation survey, as we need a mortgage. But the FSS is up to us and it was concerning that one that I was advised we would be better off doing it ourselves with care, sense and suitable advice. (We spent last weekend thoroughly poking around in the property and it does generally look in very sound condition, but we are not sure how to assess beams.)

Hilary

 

[Penners]

the fact that the beams are painted makes it more difficult to see what is going on.

Actually, Hilary, I echo what MdB has said above. If the beams have been painted this probably makes it easier to see whether there's active woodworm. The fresh flight holes should be clearly visible in the painted areas.

I can only tell you what my approach would be to your concerns.

I wouldn't pay an eye-watering amount of money for an ultrasound survey*. I'd want to have a good look at the roof timbers, and search carefully for the "frass" that Flyfisher has spoken of. But I wouldn't let the woodworm holes in the beams worry me unduly (unless I found plenty of evidence of recent activity). The chances are that there's nothing serious, and if you do go ahead with the purchase, once you've moved in you can keep a close eye on things for possible future action, if it's really necessary.

Please don't regard the above as expert advice - it's just based on my experience of my own past period houses, all of which came with a full set of woodworm holes and none of which gave any problems.



*Unless of course you want to know whether any of the woodworm are pregnant.

 

[inwood]

There are a few companies that can provide timber resistance testing using very thin drills (no bigger than the exit holes created by the escaping larvae).

In essence the system measures the resistance provided by the timber at the drill tip (high resistance - solid timber, low resistance - decaying timber). By carrying out a representative sample across the length of the timber it gives a reasonable picture of the state of the timber from the outer core all the way through.

Whilst it is invasive the damage caused is minute but would still require support of the conservation officer to carry out the investigation.

This is the tool that is used:
http://www.sibtec.com/digitalmicroprobe.html

This is one company that uses the tool:
http://www.premier-heritage.co.uk/expertise/non-destructive-timber-investigation/
but I'm sure there are more.

Hope this helps

 

[Flyfisher]

Interesting info Inwood. I guess that's the hi-tech equivalent of pressing a penknife blade into suspect beams.

Hilary, we had a FSS before taking on our house. It was very expensive (just over £2k), very thorough and scared us to bits. But, as the surveyor explained, it's his job to point out all the faults, of which there were quite a few! I then used the report as a basis to discuss all the faults with people experienced in old properties. This gave me the confidence that all the faults were things I could deal with one way or another.

In hindsight, the FSS didn't highlight anything I didn't already know about (it's failrly obvious that a roof leaks if you can see daylight through it!) but it did confirm them and formed the basis for a project plan that meant I could proceed with reasonably confidence that there were no lurking surprises - which, ultimately, is what we all want when buying a property.

So far, I've fixed many 'nasties' but at least I haven't uncovered any nasty surprises.