Moisture Readings

[pjf]

Hi,

I'm sure this has been done to death, so apologies in advance but I would appreciate some advice:

Having had an offer accepted the survey has come back quite positive and within the realms of what I expected (hoped) with perhaps one niggling exception. The surveyor comments that the hull, whilst having no visible signs of osmotic blistering or delamination (tested by hammer), does have meter reading of between 500 - 700 and he classes that as "wet". He goes on to say that this is not a real issue as boat has been afloat continually for 2+ years now and a period ashore would help her dry out a bit.

My question is: where do the levels sit within the scale? I think the range is 0 - 999 so yes I know that is 50 - 70% of the scale but what does this really mean comparatively? I'm aware that all grp hulls take up moisture to a lessor a greater extent. Does that fact that there is no sign of osmosis after 33 years mean that she is unlikely to progress to the condition?

Boat is 33 years old heavily constructed 38' sloop

Thanks

 

[PaulMcC]

To be honest I don't know much about moisture readings despite doing quite a bit of research at the start of the year. It seems that there are a few different meters commonly used by surveyors and the different meters have different scales and can be set to measure 'deep' or 'shallow' moisture. Given it is all quite confusing I think your best bet is to give your surveyor a call as he will know his meter and what is typical - get him to talk you through it. Checking with him, is this typical for a boat that age? Would he expect blisters to develop if the boat stayed in the water? What about if it comes out for some months each year? Etc..
You probably won't get definitive answers but hopefully enough of a sense to make your own judgement about how big a risk it is.

 

[rob2]

I concur, only your surveyor with a working knowledge of the meter and technique used can really hope to interpret the results. I just wonder whether the results were consistent over the whole hull or whether there were isolated high readings? As I understand it, readings can vary according to what is on the inside of the hull where the reading is taken, e.g. a bulkhead or a bilge sump, so the pattern can be important in the interpretation process.

Rob.

 

[Keith-i]

You have to be very careful with such readings. The slightest presence of salty moisture on the surface can give false readings. He should take comparative readings above the waterline to see of it is genuine trapped moisture or just surface contaminants.

 

[johnlilley]

The readings are meaningless unless they are qualified by the instrument used & the individual settings for that test. Normally when I do a survey I will list the moisture meter readings with the full settings on the unit & the type of unit as without these, any future readings have no value unless you can make direct comparisons. Again, how soon after lift out were the readings taken as if they are taken on the same day as lift out they will have no real value & will be misleading (unless they are very low to start off with). Generally you need to have the vessel out of the water a couple of days at least before you can start to get useful readings. Finally, unless there are visual indications as well as the high moisture meter readings, you would not generally undertake any invasive work on the hull simply because of high readings if hammer testing found no fault. The only caveat on this would be where a seller has seen blisters & surfaced therm flat & coated with a quick coat of epoxy to prevent the surveyor accessing the gel coat. The moisture readings would be high but no obvious visual signs...at that time. Unfortunately a common practice by some nowadays & relatively easy to do if the blisters are not too big. It pays to be very suspicious of new epoxy coatings on a boat for sale.
More information on understanding moisture meter readings on my web site if that is any use.

John Lilley

 

[pjf]

Thank you very much for your answers. I forgot to mention that the meter was a Protimeter and that readings were taken within an hour of lifting. So this I gather this would render them somewhat flawed. Is it he case then that they would also inevitably show a "high" reading?

It did look pretty clear from the condition of the hull that there hasn't been any sort of remedial or concealment type work undertaken, recently at least. The surveyor stance seems to be fairly pragmatic and his opinion is that the hull is fundamentally sound. Of course this is what I want to hear but I guess I just trying to gauge whether this is the case and not just him being a little too "laissez faire".

Thanks again

 

[johnlilley]

Within an hour of lifting....yes, totally meaningless unless as I said earlier they were very low, which on a vessel of this age would be unlikely. Protimeter readings are not directly comparable to the two main units used, Tramex & Sovereign. All you can do is rely upon the experience & judgement of your surveyor, but if there is no obvious disturbance to the hull surface such as blistering or delamination then irrespective of readings obtained, if the hull is still the original thickness & has not been "improved" recently then all should be well. Blisters are not likely to appear next week if they have not appeared in 30 odd years.

Regards

John

 

[pjf]

Many thanks for your experienced comments John, appreciated.

Regards
Phil

 

[Stemar]

More than you want to know about moisture, blisters, etc at http://www.yachtsurvey.com/index.html

 

[superheat6k]

...

Boat is 33 years old heavily constructed 38' sloop

Thanks

And likely will do another 33 before this myth becomes a problem (IMHO of course), but will possibly for reasons of no sense put future would be buyers off. So if you like the boat take advantage yourself when negotiating the price now, and be aware of its potential to delay a future sale.

 

[Laurie]

And likely will do another 33 before this myth becomes a problem (IMHO of course), but will possibly for reasons of no sense put future would be buyers off. So if you like the boat take advantage yourself when negotiating the price now, and be aware of its potential to delay a future sale.

Too true... never heard of a boat sinking because of osmosis.

Unless someone knows otherwise...???

 

[markhomer]

But unfortunately it has to be taken into consideration as said above , if you are going to spend a serious amount of money on a boat with elevated water levels , to secure you money , work needs to be done , not for any structural reason , purely to give you something you can sell more easily in the future if you have too , or get a big discount and be prepared to give , although future buyers perceptions may put them off ( unfounded or not ) .

We were faced with similar prob on boat with early osmosis , which i appreciated wouldnt sink the boat , butfellow selling wouldnt drop to pay for works , we moved on , a year later he sold his boat vastly reduced , infact at price i had offered to allow works , took him another year to realise though .

Just something to bare in mind