Wooden Boat Survey

Wooden Boat Survey

The scope of a wooden boat survey includes some or all of the following. Otherwise, the fittings and equipment are surveyed as for fibreglass (GRP) yachts.

I have extensive experience of the defects to which refitting wooden craft are vulnerable, and the best methods of repair. There are few craft more beautiful than a well-maintained wooden yacht, but you should be aware that because a yacht is old it does not necessarily follow that it was well built. For some time after 1945, good-quality timber was scarce, and there are still some dubious yachts around from that era. Similarly, some working vessels were built to have a working life of 25 – 30 years, after which they would have been discarded. Reviving those can be a costly business.


Hulls are visually inspected without removing any intact paint above the waterline. Only the antifouling may be removed below the waterline.

The planking is hammer-sounded. Spike-testing is only used where sounding indicates the timber may be soft.

Some hood-end and garboard woodscrew fastenings are drawn if permission is granted. The caulking is assessed from the external appearance of the seams. Otherwise the paint, stopping and cotton are not removed unless with special permission.

The frames, floors, and centreline members are inspected as accessible.

Hull Fittings

A selection of the keel bolts (in the case of sailing yachts) should ideally be drawn or X-rayed. The problem with X-raying is that a safe radius of about 100’ is needed, for up to 10 minutes at a time per exposure, from which all people must be excluded. That is not possible if a public footpath or road is within the safety radius. On the other hand, drawing bolts may cause them to fracture. I usually advise on the best procedure having formed an opinion of the fastenings’ likely state after the main survey has been completed.


A sound deck structure is vital on timber yachts, because it is freshwater that cause the most damage (seawater is a preservative).

The exterior planking surface is inspected, and the underside where accessible. The survey also covers the caulking, beams, shelves, clamps, partners, knees, carlins etc and their fastenings, without opening up.

Masts and Spars

Timber masts and spars are examined from deck level only, or as presented. The places these are most likely to deteriorate include around the metal bands at cap or hounds, behind the gaiter and at the heel if keel-stepped. The glue-lines on built-up masts can also suffer. Damage is usually evident from discolouration of varnish; again, further dismantling may be recommended if damage is suspected.


Common Defects in Timber Vessels

Older timber craft are usually cheaper than GRP for the same size, because of the cost of upkeep and the relative scarcity of craftsmen capable of first-class work. The timber can simply weaken due to old age and fatigue, long periods of water-logging having degraded the cell structure without actually causing rot. However, the main causes of damage are rot, marine borers, or electrolytic/electrochemical attack.


Rot is caused by fungal growths digesting the timber. If the timber is kept clean, dry, well-painted and ventilated, it is unlikely to develop. However, there are plenty of inaccessible places on the older wooden yacht that may not have been painted since it was built, and where fresh water can lie undetected. There are numerous types, but the main ones that affect boats are wet and dry rot, although the names are somewhat misleading because no timber will rot at the 18% – 20% moisture content which air-dried timber has in the UK. Dry rot needs at least 20% moisture content by weight, but the optimum is nearer 30% – 40%. However, once started it can transport water to otherwise dry wood, and hence will spread rapidly unless thoroughly eradicated. Wet rot’s optimum conditions are 40% – 50% moisture content, easily achieved in some sections of a yacht’s structure if not properly maintained.

Marine Borers

In this country Toredo ‘worm’ or ‘Shipworm’, and the lice-like Gribble are the main threats. Good antifouling coatings should be maintained to prevent attack. Yachts that take the ground, and wear away the antifouling along the wood keel etc, are particularly at risk. The presence of other rots may facilitate gribble entry into the timber.

Electrolytic Attack

This is sometimes also called ‘nail sickness’. Where there are dissimilar metals in contact or close proximity, they will set up an electrochemical cell. That produces an alkaline solution at the ‘cathode’, which will dissolve the timber. The damage can be extensive. The use of anodes for cathodic protection should be avoided on timber craft unless proven essential. Poorly-insulated or incorrectly-earthed electrical equipment may also cause rapid damage.


Fastenings suffer from wear, corrosion and age. In particular, wood-screws will act like a saw in time, and open out the holes. Copper nails will elongate and possibly fracture if frames are ‘working’ excessively. Bolts through oak components may suffer from the acid in the timber. The fastenings need to be particularly carefully considered. Refastening is quite common, and will help to prolong the life of a vessel. Good quality fastenings are essential: craft that have iron fastenings or ‘dumps’ may have only a limited life.



Call 01929 480064 or email Anthony Byrde to discuss your own requirements further