Typical Areas Included in a Hull Moisture Level Survey

---

• Review  of vessel particulars: LOA, construction type, layup method (hand-laid, infusion, CSM/WR, core type).
• Review of previous survey reports, repair records & osmosis treatment      history.
• Environmental conditions recorded: air temperature, humidity, hull temperature, recent rainfall, time since haul-out.

•  Identification of hull construction type: solid laminate, cored (PVC, balsa, PET, SAN), hybrid.
• Identification of barrier coats, antifouling systems, prior epoxy treatments.
• Visual inspection of:
  • Gelcoat condition (crazing, star cracks, chalking).
  • Previous repairs, fairing compounds, blisters, pinholes, osmotic fluid signs.
  • Wicking or laminate degradation.
• Check for voids, delamination or mechanical damage (percussion testing).

• Selection of appropriate meter frequency:
  • Low-frequency (Solid GRP).
  • High-frequency or capacitance (cored structures).
• Calibration reference on dry laminate area above waterline.
• Meter type & model recorded .
• Depth-of-field and scale interpretation notes recorded.

• Systematic grid-based survey:
• Bow sections (port & starboard).
• Mid-body sections, incl. keel bonding areas.
• Aft sections & rudder stock areas.
• Keel-to-hull joint (sailing yachts).
• Shaft log areas (motor yachts).
• Any transducer, thru-hull, or skin-fitting penetration zones.
      Readings:
• Moisture values recorded in % or meter-specific “scale” units.
• Notation of anomalous readings exceeding baseline.

• Topsides below gunwale.
• High-stress areas: chainplate exits (sailing yachts), cleat bases, pads, and deck reinforcements.
• Known water-ingress points (e.g., toerail, hull/deck joint).

• Accessible internal surfaces are inspected for:
• Elevated moisture behind tanks, batteries, insulation, bulkhead bonding areas.
• Bilge areas & limber hole pathways.
• Stringers, floors, and keel reinforcement zones.
• Water trapped between laminate and coatings (esp. epoxy/painted bilges).
• Cored hulls: testing inner skin for comparative readings.

 For balsa, PVC, SAN, PET cores:

• Moisture patterns indicating core saturation.
• Evidence of bond failure, shear cracking, resin starvation.
• High-risk hardware penetration points:
  • Stanchion bases
  • Chainplates
  • Pulpit/pushpit bases
  • Deck hardware backing plates
• Percussion testing for hollow/debonded areas.
• Thermal imaging (if available) for heat-mapped moisture anomalies.

• Identification & mapping of blisters (size, density, location).
• Sampling of blister fluid (if opened): vinegar/acetic smell, pH check.
• Assessment of laminate condition in opened areas:
  • Hydrolysis
  • Wicking
  • Resin breakdown
• Determination of osmosis stage: early osmotic activity vs. advanced blistering.

Critical structural zones:

• Rudder: laminate & stock ingress, weep holes, voids.
• Skeg & stern tube areas.
• Transom laminate, especially on outboard-powered motor yachts (transom core wetness).
• High-load structural joints: floors, bulkhead tabbing, chainplates (sailing).
• Bulkhead-to-hull bond integrity.

•   Keel (metal or composite): moisture around keel stub, cracking, weeping,      rust prints.
• Keel bolts: surrounding laminate moisture and corrosion halo.
• Rudder & bearings: moisture, delamination, seepage.
• Struts & P-brackets: moisture tracking along bonding pads.
• Stern drive mounting area (motor yachts).

• Thru-hulls, seacocks, transducers: surrounding laminate moisture level.
• Stress cracking around thru-hulls.
• Evidence of hydraulic locking in cored sections.

• Chainplate zones
• Mast step & partners
• Stanchions & lifeline bases
• Deck hardware penetrations
• Window frames & deck hatches
• Cockpit sole, locker lids, and lazarette areas

 Professional survey output usually includes:

• Drying requirements.
• Localised repair needs (laminate/core).
• Osmosis treatment recommendations (spot repair vs full peel).
• Re-inspection intervals.
• Structural reinforcement or re-tabbing if moisture has compromised structural      members.