Woodworm survey

A woodworm survey answers three questions in order. Is there beetle activity, is it live or finished, and has the timber lost any strength. Everything else, including the price of any work, follows from those answers, which is why the survey comes first and the quote comes second.

It is worth being clear about what it is not. It is not a valuation, it is not a full building survey, and it is not somebody standing in a doorway with a torch agreeing that yes, those are holes. A survey worth its fee involves opening something up, taking readings, testing timber with a blade, and writing down what was found and what could not be reached.

What happens on the visit

The order varies with the property, but the shape of a proper visit is consistent.

1. A conversation at the door. What you have seen, where, and when. Any history of leaks, burst pipes, a wet cupboard, a slate off, a hopper that overflows in heavy rain. Whether the flat has been empty, let out or recently refurbished. This is not small talk, it narrows down where to look.
2. The timber you already know about. The holes you found get examined first: their size, their colour, whether the edges are sharp and pale or grey and rounded, and whether there is frass anywhere below them. Hole size matters because 1 to 2mm round holes point at the common furniture beetle and roughly 3mm holes in old oak point at deathwatch beetle, which is a different job.
3. Moisture readings. A meter is run across the timber and the adjoining wall. Beetles thrive in slightly damp wood, so the readings say as much about whether an infestation can continue as the holes do, and they point at where the water is getting in.
4. Probing the timber. A bradawl or a penknife goes into suspect wood, particularly at joist ends, skirting backs and the bottoms of door frames. Resistance is the test. Sound timber pushes back, weakened timber gives way, and a surface that crumbles under light pressure is telling you that treatment alone will not be the answer.
5. Opening up, where you allow it. Usually one or two floorboards in an unobtrusive place, a loft hatch, an access panel to a bath or a cupboard under the stair. In a tenement this is the only way to see into the floor void, which is where the story usually is. Nothing gets lifted without asking you first.
6. The other timbers you have not thought about. Loft and roof timbers, stair strings and treads, cellar joists and lintels, the backs of built-in cupboards, sarking boards, and any timber built into an external wall.
7. A verbal summary before they leave. You should be told, in plain terms and on the day, whether it looks live or historic and whether anything structural is in question. The written report follows.

The kit a surveyor brings

Timber surveying is a low technology trade, and that is not a weakness. Most of the diagnosis comes from four things.

• A good torch. Held at a low angle, raking across the surface, because sharp edged fresh holes and pale frass show up in side-lighting and disappear under a straight-on beam.
• A moisture meter. Pin type for timber, sometimes a non-invasive meter for plaster and masonry. It gives the numbers that turn "it feels a bit damp" into a reading you can put in a report.
• A bradawl or penknife. The most useful instrument in the bag. Nothing else tells you as quickly whether a joist end is sound.
• A board lifter and a screwdriver. For getting a board up without destroying it and putting it back down properly.

Sometimes a borescope goes into a drilled hole or a gap to see inside a void, a wall head or under a stair without opening it up further, and most surveyors photograph everything as they go, because a photograph of a joist end is worth a paragraph describing one.

What the report tells you, and what it is for

A written report should cover which timbers were inspected, what was found in each, whether activity looks current or historic and why, moisture readings, what could not be accessed and why, and what is recommended, including where the recommendation is to do nothing. Photographs and a sketch or plan of the affected areas make it usable by somebody who has never been in the building.

That document does three jobs beyond simply informing you.

• It closes a lender query. When a mortgage valuation notes evidence of woodworm and the lender asks for a specialist timber report, this is the document they mean. A quotation sheet will not close it.
• It follows up a home report. Scottish home reports regularly flag timber defects and recommend further specialist investigation. This is that investigation, and both buyer and seller can commission it.
• It gives you something to negotiate with. A report saying four joist ends need replacing is a number you can take into a price discussion. So, in the other direction, is a report saying the activity is historic and the timber is sound, which is often the cheapest way for a seller to take an issue off the table before it grows in the buyer's imagination.

How long it takes and what to have ready

Allow an hour for a flat and two to three hours for a house with a loft, a suspended floor and a cellar. The written report normally follows within a few working days.

You can make the visit quicker, cheaper and more accurate with half an hour of preparation. Clear access to the loft hatch and take breakables out of the way. Move furniture off the floor area you are worried about and lift any loose rug or carpet you can. Unlock the cellar, the under-stair cupboard, the back court and the bin store if the surveyor needs them, and say in advance if a key from a factor or a neighbour is involved. Have dates: when the leak was, when the bathroom was done, when you first noticed the holes. Do not brush the frass away just before the visit, which people do out of tidiness and which removes the best evidence there is.

Why the Scottish building stock makes the visit matter

In a tenement almost everything that counts is out of sight. Joist ends are built straight into solid sandstone with no cavity and no damp proof course, so the timber and the wet masonry are in direct contact and the evidence is inside the wall. Floor voids over unventilated ground, with airbricks lost behind a flowerbed, decking or a later extension, hold exactly the humidity the common furniture beetle likes. Lath and plaster hides everything behind it. Shared gutters and downpipes under tenement law belong to all the owners and so in practice to none of them, which is how a split hopper wets the same wall for a decade.

None of that is visible from the middle of the room, which is the whole argument for a survey. It is also why a survey in Scottish property so often ends up reporting on damp and rot as well as beetles, and why one visit covering all of it, atimber survey, is usually the sensible booking if you are not sure what you are dealing with.

After the survey

If the answer is historic and sound, you are finished, and the report is worth keeping for the next time somebody asks. If treatment is needed, the report becomes the specification the quote is written against, which is what stops the job growing later. What the work involves is on thewoodworm treatment page, and typical figures are on thewoodworm treatment cost page. If you would rather test it yourself before booking anything, start withhow to tell if woodworm is active.