[Panda88]

We have a large (92x108") hot tub in a closed off area under our deck, which is largely made of spruce. This area has very little ventilation, and the windows are opened regularly only a few months of the year as most of the year it is below zero outside (even down to -30° C).

So! Our issue is that we want to prevent the spruce from rotting - without opening the windows. I'm desperately hoping to rectify the situation but it must be fairly heavy duty solution, because the ceiling (our deck) is just about 4 ft at the lowest point above the edge of the hot tub. As you can imagine, it doesn't take very much for the room to start dripping profusely from the ceiling.

I've looked into RedGard and Blue Seal, but apparently this stuff is meant to be used behind tile and whatnot. Perhaps half a dozen coats of Thompson's Water Seal is better for the situation? I'm even considering a combo solution involving dehumidifiers and fans. =\

Any suggestions would be of INCREDIBLE help.

 

[Ron6519]

Is this deck built in such a way as to keep water from getting through it?
Assuming this is true. I would think you need a way of controlling the humidity. An exhaust fan, a dehumidifier and closing up the ceiling seem like a start. I'd used a rot resistant wood, like cedar and treat that with water repellants.
Ron

 

[Panda88]

Is this deck built in such a way as to keep water from getting through it?
Assuming this is true. I would think you need a way of controlling the humidity. An exhaust fan, a dehumidifier and closing up the ceiling seem like a start. I'd used a rot resistant wood, like cedar and treat that with water repellants.
Ron

Hi Ron,

Thanks for your suggestions! Would you suggest any particular brand or type of water repellent? Hopefully something that could withstand constant moisture and possible heating/cooling (from if the hot tub was in use or not).

 

[Bondo]

Would you suggest any particular brand or type of water repellent?

Ayuh,... I'd think Val-oil, Lynseed oil, boiled or raw maybe... tonge oil,..??

 

[Ron6519]

Hi Ron,

Thanks for your suggestions! Would you suggest any particular brand or type of water repellent? Hopefully something that could withstand constant moisture and possible heating/cooling (from if the hot tub was in use or not).

Check Consumers Reports and see if they did a comparison on these. I know they've done paints and outdoor stains.
Ron

 

[Panda88]

Thanks Ron and Bondo for your input! Just updating -- I went around to some stores today and got talking to some of the sales people, one said that the easiest and most straightforward way to prevent the rotting is to remove the moisture rather than to continuously battle it. Sounded good to me -- He suggested a powerful commercial grade fan that can move 300CFM (an acronym I learned just today! Yes I'm that new).

I'm still hoping to talk to some more people before settling on this, but it was notable because...I didn't even know such fans were available for purchase, haha. Also it seems the general "expert" consensus was that a de-humidifier would be vainly ineffective in the face of our giant hot tub, so I suppose that possibility is off the list =)

 

[Ron6519]

Thanks Ron and Bondo for your input! Just updating -- I went around to some stores today and got talking to some of the sales people, one said that the easiest and most straightforward way to prevent the rotting is to remove the moisture rather than to continuously battle it. Sounded good to me -- He suggested a powerful commercial grade fan that can move 300CFM (an acronym I learned just today! Yes I'm that new).

I'm still hoping to talk to some more people before settling on this, but it was notable because...I didn't even know such fans were available for purchase, haha. Also it seems the general "expert" consensus was that a de-humidifier would be vainly ineffective in the face of our giant hot tub, so I suppose that possibility is off the list =)

I don't agree with a dehumidifier being ineffective. I agree that the wrong size dehumidifier would be ineffective.
As informed and knowledgeable as sales people are, I disagree with the premise the wood does not need to be treated. If you're sitting in the hot tub, are you having this fan run? Or are you turning it on after you get out? It would be a little chilly in there with the fan on.
What sort of space is this? Is it heated or more like a 3 season room?
Ron

 

[Bondo]

one said that the easiest and most straightforward way to prevent the rotting is to remove the moisture rather than to continuously battle it.

Ayuh,... With an Unheated deck for a ceiling, I really doubt you're gonna be able to stop the condensation....

 

[Panda88]

Ayuh,... With an Unheated deck for a ceiling, I really doubt you're gonna be able to stop the condensation....

You suggest...making the unheated deck a heated deck? Or that this is an entirely lost cause, period? =\

I don't agree with a dehumidifier being ineffective. I agree that the wrong size dehumidifier would be ineffective.
As informed and knowledgeable as sales people are, I disagree with the premise the wood does not need to be treated. If you're sitting in the hot tub, are you having this fan run? Or are you turning it on after you get out? It would be a little chilly in there with the fan on.
What sort of space is this? Is it heated or more like a 3 season room?
Ron

Ahh, I see. The dehumidifiers I've been finding have only been for residential (ie: Damp basements). If I go down the dehumidifier route, I'd need something that can stop the roof from dripping constantly.

We are still treating the wood with an outdoor weather wood stain, the brand/name of which I forget at the moment. If we go forward with this fan idea, we will have the fan run while the hot tub is open (or it is hooked to a humidistat). As for chilly...haha. This is an enclosed area underneath a deck, there is likely a few inches up to a foot of snow outside for most of the year. In the pic I took with the original post, you can see the weather outside at around -25° C that day. It definitely isn't warm in there now...!

Although, my dad does want to put a heater in...we're still looking. In this regard the salespeople were fairly unenlightening...(and so far, I kinda think that if we put the fan in, no amount of heating can keep that room warm.)