Osmosis Test and Survey for GRP Yachts in Turkey
Buying a GRP yacht that has been sitting in warm Turkish waters for years? An osmosis survey tells you exactly what is happening beneath the gel coat, before you commit. We map moisture levels across the entire hull, grade any blistering, and give you a repair cost estimate in a single English report.
An osmosis test is also called an osmosis survey, moisture survey or blister inspection.
Osmosis and moisture survey: €350-600 (excl. VAT) · boat ashore and dry for at least one week · report in 2-3 working days
Warm Water Accelerates Hull Degradation
The Aegean and Mediterranean are warm. Surface water temperatures sit between 22°C and 28°C through the sailing season. That warmth accelerates the chemical process behind osmosis, water migrates through the gel coat, reacts with uncured polyester resin, and forms acidic pockets that blister outward.
A boat kept in Scandinavian waters might develop osmosis after fifteen or twenty years. The same hull in Bodrum or Göcek can show signs in eight to ten. Charter boats, continuously afloat, rarely hauled, are especially vulnerable.
We inspect GRP hulls across Bodrum, Marmaris, Göcek and Fethiye. The pattern is clear: pre-2005 hulls that have spent their lives afloat in Turkey carry a high probability of measurable osmosis. That does not mean the boat is worthless. It means you need to know the extent, the cost, and whether it has been treated before.
Osmosis Repair Pricing in Turkey (2026)
Light (Grade 1)
Scattered small blisters, moisture readings 15-25%. Localised gel coat repair and barrier coat. Cost: €2,000-€4,000 for a 35-40 ft hull.
Moderate (Grade 2)
Widespread blistering, moisture 25-40%. Full gel coat strip below waterline, 2-4 months drying, epoxy barrier. Cost: €4,000-€8,000.
Severe (Grade 3)
Deep delamination, moisture above 40%, structural laminate affected. Full peel, extended drying, laminate repair and barrier. Cost: €8,000-€15,000+.
Prices are indicative for Turkish boatyards. Actual cost depends on hull size, yard location and extent of damage. Treatment in Turkey is typically 40-60% cheaper than Northern European yards.
Osmosis Survey FAQ
Absolutely. Osmosis is not a deal-breaker, it is a negotiation tool. If the survey shows moderate osmosis costing €5,000 to treat, that amount comes off the purchase price. Many buyers deliberately target boats with untreated osmosis because they get a lower price and then have the work done in a Turkish yard at competitive rates.
After gel coat removal, the laminate dries until moisture-meter readings stabilise and approach the dry-reference values of the same hull, checked at regular intervals. In Turkey's summer climate this takes 8-12 weeks. In winter, it can take 16 weeks or more. The boat must stay on the hard during this period. Rushed drying leads to premature barrier coat failure.
A properly applied epoxy barrier coat, typically 5-6 coats of a product like International Gelshield 200, dramatically slows water ingress. It is not a lifetime guarantee, but a well-applied barrier after proper drying can protect the hull for 15-20 years. The key word is "properly", application over a damp laminate is worse than no barrier at all.
Yes. A focused osmosis and moisture survey costs €350-€600, while a full pre-purchase survey is €450-€3,850 depending on length, boat type and age. If the hull has already been surveyed and you only need moisture data, for example, to check whether a previous treatment is holding, the standalone osmosis survey is the right choice.
Request an Osmosis Survey Quote
Send us the boat details on WhatsApp, length, location, and whether it is currently afloat or on the hard. We reply with a written quote.
Get a Quote on WhatsApp 📝 Written quoteOsmosis Test: Frequently Asked
How is an osmosis test done?
With the boat ashore, the underwater hull is scanned on a grid with a moisture meter against a dry reference area, sounded for voids and the blisters examined. Readings go into the report as a grid map.
How long must the boat be out of the water?
At least a week ashore to dry. Readings taken on a boat just lifted are high and misleading.
Scope: The survey is non-destructive and nothing is dismantled; details on the survey types page.
Findings we often see on site
- Osmosis blisters below the waterline: Blisters from pinhead to lentil size under the waterline; some weep an acidic fluid when opened.
- Wet core in the transom: High moisture readings and a dull sound in the transom around the ladder and exhaust outlet.
Notes from the field
- Not every blister is osmosis. Blisters between paint layers are often harmless; we check which layer the blister is in.
- We take the dry reference above the waterline of the same boat. The readings only mean something against that reference.
- We do not take readings until the hull surface is dry; surface water makes the laminate look wetter than it is.
Further reading
Request Your Survey Online
Fill in the form and we'll come back with an itemised written quote.
📋 Survey Request FormWhat the Survey Report Contains
See what the report contains, section by section, with finding structure and measurement tables.
⬇ See Report Contents (PDF)