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Insulating the floor on enclosed deck to make it into a 4 seasons room

Insulating the floor on enclosed deck to make it into a 4 seasons room

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  #1  
Old 12-30-16, 12:08 PM
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Insulating the floor on enclosed deck to make it into a 4 seasons room

We bought a house a year ago and the former owners enclosed a deck for a hot tub. We had them remove the hot tub and we want to turn the room into a 4 seasons room. We want to insulate the floor which is two different levels. One side we can crawl under, on the other side, we will need to take up the deck boards. (See pictures as the deck is close to the ground about a foot on one side and 6 inches on the other) Looks like the former owner put some sort of tarp on the ground. We live in Eastern PA. I have been researching different ways to insulate, one builder suggested a closed cell foam insulation for a shed, which is similar to my situation, however, I'm not sure that will keep out critters and pests? I saw another video that suggested Roxul ComfortBatt R30. I am considering using the Roxul with PT Plywood to keep critters and pests out. However, I'm not sure if I need a vapor barrier or not. We want to lay a sub-floor and then hard wood. Would the following layering work...
Hardwood
Subfloor
Vabor Barrier (under subfloor on top of Joists)
Roxul Insulation In between joists
Pressure Treated Plywood under joists in the higher deck side (where we can get underneath) and in between the joists where we can't get in between the joists on rails or metal cleats. Thoughts about the layering of material? If correct...what type of vapor barrier would you recommend?
Thanks in advance for the feedback.

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  #2  
Old 12-30-16, 02:29 PM
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Pictures made me dizzy, but I get the drift. Yeah, Roxul requires no vapor barrier, but I would install one anyway since you are so close to the ground. You will also need to install 6 mil plastic on the ground and enclose the sides in some manner. If you are going to be removing the decking boards, you can cleat along the joist bottoms and drop in individual pieces of plywood to help seal from the critters. Then install the Roxul from above along with your other layers.
 
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Old 12-30-16, 02:48 PM
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This is such a bad idea... dont even know where to begin.
 
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Old 12-30-16, 03:30 PM
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So you are basically taking a deck and converting into a living area?

There is so much difference between the two I dont even know where to start!

First question, was there ever a permit pulled to do the original inclosure?
 
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Old 12-30-16, 04:01 PM
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This structure was never meant to be enclosed and used as living space, stories like this usually do not end well.
 
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Old 12-30-16, 06:44 PM
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Thank you for your reply. What would you use for the vapor barrier between the Subfloor and the Roxul? The former owner insulated the walls but not the floor or ceiling. He used vinyl vented soffit for the ceiling, which we took down so that we can insulate. If we don't insulate the floor and ceiling and heat/air condition it, the room is somewhat useless as it is way to hot in the summer and too cold in the winter to use. See photo. Keeping my fingers crossed and hoping for the best.
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  #7  
Old 12-30-16, 06:53 PM
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The previous owner enclosed the deck and got permits for enclosure and final inspection approved. He insulated the walls and ran electricity.
 
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Old 12-31-16, 04:40 AM
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I see from the picture you have no plans on removing the deck boards. What do you plan on having for a finished floor?

You need soffit vents into the rafter tail area with baffles installed all the way up to the roof's peak so air can move from low to high. THEN you can insulate under the baffles. Air movement is critical in insulating a vault like you have.

What is the rafter block for in the upper right corner of the picture? Skylight?
 
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Old 12-31-16, 07:18 PM
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1) We are removing the deck boards on the lower half of the room as we can't get under it to insulate. We are going to finish with a hardwood floor. Soffit vents are already there. (See Picture)
2) We plan on doing a radiant barrier and insulation rails to leave an air gap like the attached picture for the ceiling. (See Picture) The insulate with Roxul and drywall.
3) Yes, The rafter block is a skylight.
4) My only concern now is that there are two areas where the previous owner did not make the enclosure flush with the side of the deck. At one spot, he left part of the deck with the stairs and at the other spot, he left a about 4 inches of deck exposed. Suggestions on how to keep water from going under the J channel and getting into the wall/floor? (See Pictures) Not sure why he didn't make it flush, especially on the one side without steps, so frustrating. Suggestions?
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Old 12-31-16, 07:50 PM
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On the exterior, you would need to remove the bottom row of siding and pull bottom nails in j-channel, get a metal brake and bend a custom z-flashing that goes in the gap between the decking boards. Flashing goes behind the WRB if they even used one. Even then, blocking between joists would need to be kept back behind the z-flashing or else insulation between joists could get wet when water blows back. IMO, all decking thats inside the exterior walls should be removed, (flush trim saw) all joists should get cleats, (upper and lower) all bottom sheathing should be treated plywood dropped onto the cleats and all edges of that plywood should be air sealed after it is installed. After insulation is installed, (no poly vapor barrier, only kraft faced so that it is semi-permeable) go back with 3/4" t&g Advantec then your floor, then baseshoe. Also IMO the radiant barrier is a waste of time and just reduces your insulation. I would spray foam it full, which is what's normally done when venting is pointless (there's no exhaust when the rafters dead end into a 2nd story ledger / wall) in order to get the most r value possible in areas where there is a minimum of rafter depth.

Still think it's a bad idea but can tell there's no stopping you. Its still going to be hard to climate control, being surrounded by exterior surfaces on what... 5 sides?
 
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Old 12-31-16, 08:25 PM
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I've stated my agreement with X already on this being a bad idea but also agree he's correct that you're not going to listen to such comments so I'll just say that you should be prepared with an additional heat source for this room, it is going to be cold in the winter.
 
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Old 12-31-16, 09:22 PM
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Thanks for the response. Here's a diagram of what I have going on. See pic.

What about the foundation? The former owner had to have reinforced it since he had a hot tub. If I'm removing the floor decking, do I need to add some more piers?

I have to do something to this room to make it usable. As of right now, it's a waste of space in the summer and winter. Insulating can't be worse then what I have going on right now.

If it's a bad idea, what is a good idea? Leaving as is? Is there no way to turn this into living space....

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  #13  
Old 12-31-16, 10:10 PM
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It was probably great as a deck, covered deck, or even as a screen room until someone got the bright idea to completely enclose it. I guess if you are dead set on insulating and finishing it because you feel you can't go back, we want you to honestly know the challenges you face in going forward. Plus, if and when the house is sold someday, a buyer might think twice when their inspector points out the non-standard / unusual / highly suspect way the room was constructed... even if you try to do every thing right... its still an anomaly. At that point it could become a liability.

We certainly can't say whether it needs more piers, we don't know anything about where it is currently supported, and don't know the size of joists and/ or beams. The posts look to be 4x4's which aren't really approved anymore, in some locations I guess it would be fair to add... and carriage bolting beams to the sides of posts is also no longer approved by most places where you get inspected. Granted, it may have been approved once upon a time but nowadays it appears very substandard. And that was when it was just a deck... now it's a room with walls, roof and snow load. Beams nowadays need to sit on notched 6x6 posts. Pretty hard for us to say what all it needs structurally. We don't know anything about the footings, etc.
 
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Old 01-01-17, 12:29 PM
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According to the Sellers Disclosure it was done 9/2005 and was permitted and inspections were obtained and approved. Not sure how it passed inspection unless the codes changed in the last 10 years. I agree with you as it would have been a great screened in porch but now I'm between a rock and a hard place. I either insulate the ceiling and floor and possible reinforce the foundation or leave as is. I guess I'll have someone come out to look at the foundation.
 
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