Teak vs Ironwood Hull — Ulin, Teak and Bitti in Indonesian Wooden Yachts

By Wooden Yacht For Sale Editorial Desk

A teak versus ironwood boat hull is usually a false choice: Juara Holding Group builder sites describe ulin for keels and main structure, teak for decks, trim and interiors, and bitti for frames. We found no reliable lifespan figure.

Listings tend to use timber names as selling points. This guide explains what each species is actually doing in the boat, which claims you should test, and what a surveyor can and cannot tell you.

Which three timbers do which three jobs?

Juara Holding Group builder sites describe a division of labour. Treat this as builders' reporting and not as neutral research, and confirm what is in the boat you are viewing.

Why are keels built from ironwood?

Ulin is Eusideroxylon zwageri. NParks Singapore lists uses that include ships, wharves and other heavy construction, and notes that the timber is hard and quickly dulls saws and cutting tools. Published density figures vary with provenance and moisture, so we do not quote one here. It is enough to know the timber is very heavy.

That weight and hardness cut both ways. They suit a backbone that takes grounding loads and carries the structure. They also make drilling and fastening slow, and bad drilling can leave a fastening with less grip than it should have. So ask how the keel and floors are fastened, and whether anyone has looked at those bolts.

Provenance matters too. Reference material reports ulin as IUCN Vulnerable because of extensive logging, and notes export restrictions in Indonesia and Sarawak. That secondary source needs checking against current rules before you buy timber for repairs or plan an export.

What does teak do, and what does varnish demand?

Teak is Tectona grandis, and it is much better documented. The USDA Forest Products Laboratory describes durable heartwood, and CIRAD rates it for use class 5, which covers regular exposure to salt water. World Agroforestry data commonly cites a density of about 610 to 750 kg per cubic metre at 12 percent moisture.

Note the limits of those claims. The heartwood is resistant to borers, not immune, and the sapwood is far less durable. The Wood Database reports teak as not listed by CITES, though sourcing from particular countries can still raise legality questions.

The same natural oils that help teak in service can get in the way of finishes. Technical sources note that oils may cause gluing problems unless surfaces are freshly prepared, and that they can interfere with varnish adhesion. Keep that in mind when reading "beautiful brightwork" in a listing, because bright finish is a recurring job. See our wooden yacht maintenance schedule for how that work fits into the year.

Why does bitti turn up in the frames?

Builder sources in the group name bitti as a framing and hull timber in South Sulawesi, where UNESCO identifies Tana Beru, Bira and Batu Licin as boatbuilding centres. UNESCO's record also describes skills being handed down through families and through a division of labour.

Beyond that, we hit a gap. We could not find an authoritative marine-borer rating for bitti, nor a confirmed current conservation assessment. If a listing relies on bitti below the waterline, ask for local service history and let your surveyor comment. Lack of a published rating does not prove a weakness. It just means nobody has handed you the evidence.

Why does drying time matter in a survey?

Timber shrinks as it loses moisture. Build with it too green and the movement happens inside the finished boat, opening seams and loosening joints. It is reasonable to ask how long the timber on your boat was seasoned.

A straight answer may be hard to come by on a used hull, since records rarely survive. That's why a surveyor's physical findings count for more than the story: seams that keep reopening, cracks at fastenings, and joints that have moved all say something.

Do not lean on a moisture meter here. Boatmere notes that readings are of limited use because hull timber can legitimately carry a high moisture content.

How do you check timber species on a used boat?

Painted hulls hide their timber, and "teak" is sometimes used loosely in sales language. Practical steps:

1. Ask the seller to state species by part in writing: keel, frames, planking, deck, interior.
2. Ask for builder records or refit invoices that name the timber.
3. Have the surveyor note the species where it can be seen, and mark anything unconfirmed.
4. Look at repairs specifically, since a later plank may differ from the original.
5. Ask for the contract to carry the specification as a stated description.

Our wooden hull survey guide covers the wider scope. For European yachts built from oak, pitch pine or mahogany, the same logic applies with different timbers, and our page on the classic wooden yacht market explains that side of the field.

How long will the hull last, honestly?

We have no third-party source that gives a reliable lifespan for a teak or ulin hull in Indonesian conditions, so we do not print a number. Any figure would imply a precision the evidence does not have.

Life depends on things you can examine: timber quality, fastening material, ventilation, leak history, antifouling discipline and how often the boat comes out of the water. Cali Coast Marine Services ties rot to trapped moisture and poor ventilation, which makes upkeep at least as important as species.

Ask the surveyor what the condition suggests about the next few years of work. That is a more useful question than how many years the boat has left.

What do buyers ask about hull timber?

Quick answers on species. Where sources run thin, in particular on bitti, we say so instead of filling the gap.

What is ironwood ulin?

Ulin is Eusideroxylon zwageri, also called Borneo ironwood, a very heavy and durable tropical hardwood. NParks Singapore records it for ships, wharves and other heavy marine work, and notes that it blunts tools quickly. It is reported as IUCN Vulnerable because of logging.

How long does a teak hull last?

We have no third-party figure and will not offer one. Life depends on timber quality, fastenings, climate, ventilation and maintenance, and two hulls of the same age can be in very different states. Ask a surveyor for the condition of the boat in front of you.

What wood is best for a boat hull?

No single species wins every job. Juara Holding Group builder sites describe ulin for keels and main structure, teak for decks and trim, and bitti for frames. Sound heartwood, proper seasoning, suitable fastenings and good upkeep matter more than the species name on a listing.

Is teak immune to shipworm?

No. Technical sources call teak heartwood resistant rather than immune to marine borers, and sapwood is much less durable. Bottom protection and regular haul-outs still apply on a teak-planked hull.

Is it legal to buy a boat built from ulin?

Buying a finished boat raises different questions from buying raw timber, and we cannot give a legal view. Indonesia and Sarawak are reported to have restricted ulin exports, so if you plan to export the boat or buy timber for repairs, ask a lawyer and customs adviser in writing.

Which sources support this page?

Checked by the desk in October and November 2026. A source being listed does not mean the source agrees with us or has reviewed this page, and limited-verification items deserve a second look before you rely on them.

• Juara Holding Group builder source, timber species (group site, not neutral market data; no link given)
• USDA Forest Products Laboratory, Tectona grandis
• CIRAD Tropix, teak data sheet, 2026
• The Wood Database, teak
• World Agroforestry, Tectona grandis profile
• Wikipedia, Ulin (secondary source; check primary sources)
• NParks Singapore, Eusideroxylon zwageri
• UNESCO, Pinisi, art of boatbuilding in South Sulawesi
• Boatmere, Surveying a wooden hull
• Cali Coast Marine Services, wooden boat maintenance guide

Written and checked by the Wooden Yacht For Sale Editorial Desk.

Where do I send questions about a specific hull?

If you have a listing and want to know what to ask about its timber, send a buyer brief through the buying guide, or reach the desk on WhatsApp 6281139414563 or at bd@juaraholding.com.