Tyvek house-wrap under decking and over pour in foam????

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thill

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I decided to pull out the floor of the 1996 Spectre 16 sport. The wood was still solid, but is really waterlogged. Super heavy. I figured that the foam underneath it would be completely soaked too.

When I pulled up the flooring, I was surprised to see house-wrap underneath it. Huh??? Pulled back the wrap, and surprise-surprise, the floatation foam beneath was dry, and the aluminum stringers look super shiny and new. Shocker!! Looking at the carpet and rivet pattern, I'm pretty sure this is the original floor, so this must be a boat builder thing, but I've never seen this used before., and I've pulled a lot of boats apart.

House wrap is supposed to be waterproof, yet it allows water vapor to pass through. Has anyone else ever seen this used under a floor?

I like what I'm seeing! A simple concept that seems like it wouldn't work, but there is the proof. I'm thinking about putting fresh Tyvek under the new floor, and I might be using this in the future. I LIKE having nice, dry foam in my boat. In this case, it saved me a LOT of extra time and money not having to dig out the old foam and replace.

Let me know if you have any thoughts on this.
 
That's a great idea. I think I'll give it a try on my Mako project when I replace the floor. All the foam will more than likely be replaced at that time.
 
Depends!! I can see pros and cons....in this case, it appears the moisture cane from the top, thus the dry foam, but I think in most cases the moisture would come in thru the hull/ bottom, so now that moisture would be trapped by the wrap...trapped moisture in summer equals mold...if I were sure that no leaks or water entry came from the bottom the wrap might be a good idea....nut not sure....am I missing something here ?
 
I was thinking like you, Airshot. It seems that this boat is water tight. It has a no-rivet design through the hull, but it could still get water from the bilge.. Fortunately, the center area drains well

Unlike 6 mm plastic, Tyvek allows water vapor to pass through, so evaporation may help keep things dry.

When I have seen plastic sheeting in old boats, it's always broken up like potato chips. This stuff looked great. I'm definitely going to use it when I put the floor back in.
 
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I can't say I've seen that before. I'm wondering if it contributed to the water-logged wood?

Was the wood pressure treated? Maybe used for a "barrier" betweeen it and the aluminum?
 
Excellent, FuzzyGrub!

I signed on tonight just to post that the wood WAS pressure treated. That explains why it was still solid, despite the moisture and age of the wood. Great guess, I wouldn't have thought of that.

The fact that there was no corrosion on the aluminum and the foam was also dry is a testament to how effective the Tyvek trick is. I'm definitely going to use it.

I have two sheets of 1/2" PT that I've been saving for a rainy day. My plan is to cut them to fit and then saturate them with Thompson's wood preserver/waterproofer. I probably sound like a broken record, but Thompson's is awesome. As long as you saturate it well, especially the edges well, the wood remains waterproof. I always do 2 applications, just to be sure, and I have decades of success under my belt.

After that, I'll lay the Tyvek and install the new floor as usual, but I need to deal with the transom first. They always turn out fine, but I always feel nervous beforehand, like they will never be right again. Pre-sawzall jitters, I suppose!
 
Since the oem floor went 27 years, having well sealed PT should go much longer. :)

Curious to what the oem floor covering was? Paint, vinyl, carpet?
 
There was a change in the chemicals used in PT wood around that time. I built my home during that period when the " new and improved" PT wood was brought to market. I am wondering if the newer version is less harmfull to aluminum?? I built a deck on the back of my home that I planned on enclosing in the years to come, but as life happens, plans got changed. The deck was made of regular and PT lumber and treated lumber was used for landscaping projects. This new version of treated lumber has all rotted and deteriorated while the untreated lumber is still not to bad, far better condition than all the new improved PT lumber!!!! Neighbors have had the same experience with the new stuff. My thoughts are that the new treated lumber may not be as corrosive as the old, it certainly does not hold up in weather conditions, even talked to home depot, and they agreed, the new stuff is no where as weather proof as the old...food for thought......
 
The new ACQ and copper-based PT wood is nowhere NEAR as durable as the old PT. Very often, it is made using a terrible grade of wood to begin with. I am NOT thrilled with it. On jobs, we spend the small fortune to pay for ground-contact versions.

This is another reason I seal the wood, including PT, with Thompson's. Everything is made cheap nowadays.

For what it's worth, my Princecraft is SYP plywood sealed with Thompson's under carpet, and it's holding up great. Not sure how long, maybe 6-7 years, now? I'd have to check my tinboats.com posts from years ago.

Fuzzy, that boat has blue carpet inside. Doesn't help with moisture, that's for sure!

I've heard that the newer chemicals are not as reactive with aluminum, but I wouldn't trust it, especially when I can lay a sheet of house wrap down and not have to worry, and it has the side benefit of keeping the foam dry. That is a win-win situation if I've ever seen one!
 
The new ACQ and copper-based PT wood is nowhere NEAR as durable as the old PT. Very often, it is made using a terrible grade of wood to begin with. I am NOT thrilled with it. On jobs, we spend the small fortune to pay for ground-contact versions.

This is another reason I seal the wood, including PT, with Thompson's. Everything is made cheap nowadays.

For what it's worth, my Princecraft is SYP plywood sealed with Thompson's under carpet, and it's holding up great. Not sure how long, maybe 6-7 years, now? I'd have to check my tinboats.com posts from years ago.

Fuzzy, that boat has blue carpet inside. Doesn't help with moisture, that's for sure!

I've heard that the newer chemicals are not as reactive with aluminum, but I wouldn't trust it, especially when I can lay a sheet of house wrap down and not have to worry, and it has the side benefit of keeping the foam dry. That is a win-win situation if I've ever seen one!
My concern is a small leak from the hull and never allowed to dry out from the wrap...wouldnt that cause mold and mildew issues?? Keeping moisture trapped is never good...or an I missing something here?
 
That would be my normal thought pattern too, but no mold or mildew in this boat at all. None. The foam and aluminum under the floor is pristine. I'm somewhat amazed by it, hence this thread.
 

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