Moisture readings from survey

dlochner · Aug 18, 2021

At least in the US, I am not aware of any requirement for surveyors to recalibrate or certify their moisture meters.

Moisture meter readings are probably best view in relative terms rather than absolute terms; one place may have a reading of 20% (A) and another 30% (B). In this case B has more moisture than A, but it does not mean that A actually has 20% moisture and B 30%, A could be 30 or 40% and B 50 or 60%. The safest interpretation is that A is wetter than B.

Some of the interpretation also relies on where the high moisture readings are. Hi readings near a stanchion base may indicate a leaking stanchion base. Just reporting Port side vs Starboard side isn't very helpful. Does he mean the whole deck? a few small sections? One small section?

If you are buying an older boat it will be difficult to find a boat with a completely dry deck core. Almost all have some wet core in places. There are too many places for leaks to occur and some maintenance, like rebedding stanchion bases are a PITA and don't get done.

smokey73 · Aug 18, 2021

I doubt very seriously if the instruments used by surveyers are traceable to the National Bureau of Standards. For that matter, I doubt if they are ever checked for accuracy with a calibration check against a block of known moisture content. Add to that the variables associated with non-contact moisture meters (the scanning kind, not the metal probe type) that calibration would not be practical.

Alan Gomes · Aug 18, 2021

Understanding The Moisture Meter - Marine How To

The Electrophysics CT-33 Moisture Meter I've always been a big proponent of boat owners, and more importantly boat buyers, owning a moisture meter. I don't suggest this because I want every DIY boater to think they are a surveyor, or to

marinehowto.com

Don S/V ILLusion · Aug 18, 2021

If you ask the surveyor those questions, what you hear in response should demonstrate if or how well he understands what was reported.

Scott T-Bird · Aug 18, 2021

Spell check is making it a little bit difficult to understand your post. Are you buying or selling the boat?

Gaston1953 said:
I'm seeking the sailboat and this worries me that I will not be able to sell it.
Any help would be appreciated

"off scale" probably means that the moisture reading is beyond the limit of an accurate reading. Delmhorst pin meters that I am familiar with read wood only up to 40%. Anything greater is saturated with water and a reading greater than 40% would essentially be meaningless. So if he has accurate readings of 50% or greater, the core is essentially saturated I'd bet.

Like David said, some context would be helpful. What areas are you talking about? The meter could be picking up signals from unintentional sources. Did the surveyor offer any explanation in his report? (Perhaps you don't have the report yet).

Sailfanatic · Aug 18, 2021

Gaston1953 said:
I recently got a survey done last week and all was very good. The hull sounded good,no blistering... Over all good.the only issue I see from survey is the mixture readings. He stated starboard side 50% and port side 100%. When he was doing it he mentioned the reading on port side was off scale. What does off scale mean. I'm assuming he had a bar graph meter and and all LEDs were lit.
I read an interesting article by Practical sailor about how something like 40% of surveyors don't know how to read or interpret the readings or use one. It states meters can read and give you a percentage number or a bar graph. When he said off scale and not a percentage im wondering what is off scale? Is he saying off scale is 100% humidity? Or his met Dr can only measure lets say 50% so full scale must mean 100%. Also I worked 30 years a biomedical engineer for phyzer and Johnson &. Johnson and we had at least 50 different meters which all had to be recertified each year and provide hospitals which the calibration certificate if they requested it. Do you know if this is a requirement for surveyors. I'm seeking the sailboat and this worries me that I will not be able to sell it.
Any help would be appreciated

Did the surveyor refer to readings of the hull or of the deck. Assuming you mean the hull, is the hull cored? If you talking about an area that has core, then high moisture readings will usually coincide with some level of delamination.

Ward H · Aug 18, 2021

A couple of points.
The moisture meter in the link given by Alan Gomes comes with a copper plate which is used for calibration of the meter.
Does the surveyor know sailboats? I believe that Hunters embedded plates in the deck for mounting hardware? Metal in the deck will cause meters to give high false readings.
You don't indicate the age of your boat. As David said, an older boat will probably have some level of moisture in the decks.

Saying it's in your best interest to reseal deck fittings is a "duh" statement.

dlochner · Aug 18, 2021

Gaston1953 said:
Funny thing is another survey was done 3 weeks before (long story) but moisture readings was 7% starboard side and 17% port side of deck. I can't believe the total difference.

Gaston1953 said:
moisture readings taken of the main decksand coach roof found high levels of moisture to the following areas.
- starboard sideside deck 50%
-port side deck 100%

These surveys are consistent in that the port side of the deck is wetter than the starboard side. In each case the the port side is about twice as wet as the starboard side. The question is, how wet is the port side?

If this was a million dollar boat, then a core sample would be taken and the moisture measured directly by weighing the sample, then drying it and weighing it again. The expense of doing this and repairing the core hole is more than the buyer will want to spend.

If a broker is involved, I'd discuss this with him. He wants to sell the boat almost as much as you do.

Scott T-Bird · Aug 18, 2021

What does the deck feel like? Is it spongy or is it solid? I basically think that in some instances way too much is made of the fear over moisture in the core on a deck. You can sail a boat for years with excessive moisture in the deck. There is no reason to get your panties in a bunch over it. How old is your boat? Is it 30 years old? Of course it isn't perfect. Nobody will ever find one that is. Price it according to the market. I'll bet that shoppers will be happy to accept it, warts and all. Besides that, it's repairable. Let the next owner repair if they want to. If there is enough positive about the boat, it will sell at market price. If it's a mess, it won't. It's not that complicated. Very few buyers expect to find an older boat in mint condition. It sounds like the readings took you by surprise. If you had excessive moisture in your decks, I suspect that you would know it without even having to use a moisture meter to find it. If you have a boat that you didn't honestly expect to find moisture, I'd bet that very few buyers would get all that excited about moisture readings that could very well be a false positive. If you were aware of moisture all along, just price the boat accordingly and be done with it. Somebody will find it worthwhile even with a little moisture. I have a hard time believing that you would have a vast area of 50% moisture and not know it until the meter turns it up. Either you are not honest about the condition of the boat or the meter is a fraud. Since it turns up readings exceeding 40%, I'd suspect the meter is a fraud.

shemandr · Aug 19, 2021

Re-sealing deck hardware after the deck core is wet is a horse-barn door situation. As a buyer if I see new sealant around stanchions or deck hardware I would be suspicious of leaking or deck core issues (Do you have water intrusion into the cabin?) And, to re-seal correctly is a lot of work which will take a good deal of time. The deck core will still be wet.
I would do as Scott says: Sell it "As is" and let the next guy deal with it or not deal with it. His surveyor, if he uses one, may find the deck acceptable.

shemandr · Aug 19, 2021

You should look on Mainesail's website at Compass Marine. I'm almost certain he has posted on the subject of moisture meters. I don't want to mis-quote him so I won't hazard a summary.

Siamese · Aug 19, 2021

shemandr said:
You should look on Mainesail's website at Compass Marine. I'm almost certain he has posted on the subject of moisture meters. I don't want to mis-quote him so I won't hazard a summary.

Second that.

I recently bought a used sailboat, and had a surveyor inspect it. I was present. We were looking at the stuffing box and he didn't couldn't tell if it was dripless or not by looking at it. What a dope. It was conventional, not dripless...obvious. I'm sure there are good surveyors out there, but I'm also sure there are plenty of bad one masquerading as good ones.

Barnacle Bill · Aug 30, 2021

Instead of asking us, you should be asking the surveyor who did the survey. You are paying him for information. You might as well insist on accurate findings and not be wondering what the implication is. I would think "off the scale" would mean you have high levels of moisture. What they are testing would be moisture in the hull or in the deck. If the boat was pulled for the hull inspection and the moisture meter was placed on the wet hull, then unless it is one of the more expensive meters that differentiates the surface from the inside of the lamination or core, you'd obviously get a 100% moisture content reading. Some surveyors will insist that the boat be out of the water for something like 72 hours before checking for moisture. Obviously if the boat was stored on land, this would not be a concern. An old boat is not going to be totally dry. So, unless there is a high level of moisture in the reading, your concern might not be so crucial.