Should osmosis be treated?
The majority of GRP hulls are over engineered and therefore a surface blister which has not penetrated the hull too far is unlikely to cause a problem, particularly inland. If you are unsure about whether your craft requires attention a surveyor may be better employed to advise than an osmotic treatment centre that wants the business! If the decision is made to have treatment undertaken the boat could well be out of commission for 12 months (though the new HotVac system is now dramatically reducing this time), cost a lot of money (in excess of £200 per foot!) and the condition in many cases will not be guaranteed not to return if the moisture has not been successfully removed from the hull. I generally recommend lifting the boat out of the water at least every other year as the best control for osmotic blistering. Osmosis on a boat will not bite you and is very unlikely to cause your boat to sink. It is only ever an issue at point of sale and most surveyors these days accept and advise that craft with blisters are acceptable. In fact most surveyors become concerned when they see older craft without blisters and try to work out why! So, our advice is to buy a craft with acceptable blisters and enjoy, rather than spending a fortune in time and money finding a boat without blisters to then worry about osmosis appearing! This beats time and money spent maintaining wood and steel craft any day.