Concrete slab and storage question?

[nikolai]

I was having a debate on another forumn regarding storing wooden boats. A quick history of me. I used to build wooden boats in both NH and WI. NH I built a double ended norwegian designed Snekke. In WI I worked for Streblow boats. Helped restore, maintain, and build from scratch several mahogany run abouts.

Back to the debate. I was taught by both my mentors that you should never store a wooden boat, during the winter months, in a garage that had a concrete floor. Even when we would haul in a boat to work on it over the winter we would wet down the floor through out the day. The explanation to me was that the concrete will draw moisture to it. Thus resulting in the boat drying out. This was not a problem in the storage shed due to the fact that the floor was simply gravel. Am I correct in this assumption? I even recall working on one boat where it had been stored for sometime in a garage and we ended up bascially flooding the boat for several days untill the planks swelled back up.

It has been several years since I left the boat buisness but I'm pretty darn sure I'm right on this one. If I'm wrong please do let me know.

Thanks,

Nikolai

[Thad]

You are right.

[nikolai]

What is the reasoning behind this. Is it that concrete continues to cure thus drawing moisture in or is it that it seals the ground thus less moisture is allowed to enter the space/shop? Does an unfinished gravel floor allow the ground to breathe in a sense?

[Dan McCosh]

Having stored while hauled for a lot of years on a variety of surfaces, I always wondered why this "old wives tale" persisted. Finally, while stored on concrete it became obvious. The cement was reflecting considerable radiation to the hull, like an opaque mirror. The difference in heat on the bottom planking compared to the shaded side was substantial. The radiant heat absorbed by asphalt is similar--it warms up rather quickly in the sunlight. Anyway, that's my theory. A rug around the boat would eliminate the effect, I think, although in our case bad drainage left water standing around the hull that eliminated the effect quickly. Anyway, that's my theory.

[Ron Williamson]

Water is constantly evaporating from the ground.Concrete is less permeable,especially with plastic under it.

That said,in this warm foggy weather there is about 1/4" of condensate on my well chilled garage slab.
R

[P.L.Lenihan]

Yup,you're on the right track. A friend stored his 43 Egg in a shed with a concrete floor 7 years ago. Come Spring(launch time) it took three fire dept. pumps a little over 5 days to get the flow under control to the point where his own pumps could take over. This was the first time in several decades of ownership that he stored his boat that way and he never ever had such an experience in the past when stored on dirt. The boat has not been the same since and now requires at least a day and a half in the slings after launching.

Peter