Enclosing an existing Screened-in porch.

My question revolves around what complications I might run into in fully enclosing my screened in porch.

I am considering fully enclosing an existing screen porch. The house I live in is a 30yr old cape but the porch itself is about 12 years old. It is cantilevered off of the main part of the house and sits on 4ft deep concrete footings that are about 6ft apart. The overall dimension of the porch is 12'X16'. The porch flooring is constructed of 2x10 or 2x12 treated lumber with 2x6 treated decking. There are 4x4 treated posts approximately every 3-4ft. My kitchen opens up into this porch through a french door. As you go onto the porch you have to step down (1 step).

I am considering removing the posts and replacing it with a fully framed wall with windows all the way around. I would like to find out about what is necessary in order to insulate the floor. I thought I could keep the 2x6 deck boards and sheet over that. In terms of heat for the room, I have a accessible pipe from the forced hot water system in my house. I was thinking I might be able to install a radiant heat floor system but I am unsure of possible complications.

I have read some of the other posts. I can say that my porch is very well built. The flooring is actually more sturdy than the floor inside the house. The roof is also very well constructed and has a nice grade that allows for adequate removal of rain water and melting snow.

I am not so concerned with the actual framing, finishing, and electrical. i already have a good idea of what needs to be done there.

Questions to consider:
Should I do any additional foundation work or perhaps close in the space underneath the porch?

What should I use for insulation? Spray foam or standard fiberglass?

Should I put sheeting on the bottom of the porch to help seal out potential moisture and cold air?

Should I use Radiant floor heating solution or stick with the base board radiator solution from the rest of the house?


Thanks for you time and consideration in this matter.

Best regards,

Jonathan A. Hoskins

 

What is your location? How cold are the winters in your area?

 

I live in southern Massachusetts, near Providence, RI.

 

I just finished my third one in a row on the same road, so maybe I can give some insight. Granted mine are in the South, so you will have to adapt to colder wx.
1. Sounds as if the structural support is adequate.
2. I used R 30 kraft faced insulation under and covered the bottom with rough sawn cedar plywood with cedar 1x2 strips over the joints.
Walls were 6" walls, so R19 in the walls.
3. Heating is a choice, but if it works for the remainder of the house, why not keep the same type in this room? The owners here opted for a small heat pump to assist their house heating and cooling. Works pretty good.
4. With no advertising intended or offered, go to www.chandlerscarpentry.com, and click on Projects one. This may give you some help on what you can do in your situation. Post back as you go along and, as you may already know, there are a good group of pros and others diyers, that can give great advice.

 

Thanks for your insight. I will be sure to check out the site you listed. I never thought of using Cedar to cover up the underside. I know I need to do something, just wasn't sure what yet.

Thanks

J

 

Does anyone else have any advice for me?

 

My only suggestion would be to remove your current 2x6 decking that is likely not glued and screwed to the joists, and is probably a little bit twisted and uneven in places. Once removed, you could install 1x2 cleats onto the sides of your joists (at the bottom) then drop in 1/2" exterior grade plywood, gluing and screwing the edges to the cleats. Then you would be able to lay fiberglass batts in between the floor joists. (ISO or XPS insulation could also be added between joists if more R-value is desired.) You'd do all this from above, rather than laying on your back underneath the room. Once that's done, you would be ready to sheath the floor with a minimum 3/4" T&G plywood, OSB or Advantec. Sleepers could be installed on top of the floor joists prior to this if raising the floor is an issue. Once the deck is on, you could frame your walls. But I wouldn't lay the floor over the top of those treated boards.

And be sure all your fasteners that penetrate the PT wood are corrosion resistant, suitable for contact with your type of PT wood.

 

Thanks for the additional input XSleeper. I had considered removing the 2X6 decking. what your saying makes sense to me. It is helpful to have multiple points of view before taking on a task like this.

Best regards,

J

 

I noticed that I was mistaken about the cement pilars The Deck is 12X16 and there are 5 pillars total.along the 12' side they are 6' apart and along the 16' side they are 8' apart. In the middle of the side that is against the house they left the existing concrete stairs. I dug down about 2 feet on one of the columns and I did not reach the bottom. I am wondering if I should consider getting a poured foundation that goes 4' down or if the concrete pillars are enough. The room is already pretty much done if in terms of floor support and room if I can keep what I have. Any advice on the foundation would be appreciated. I am also concerned with moisture from below if I dont put in a poured foundations. Thanks in advance for the assistance.

J

 

Unless I missed it, you don't say how far above grade the bottom of the deck is. Just as cold air under a highway overpass causes the surface to ice over before the road does, cold air blowing under the deck will increase your heating load. If it is reasonably close to the ground you might want to consider closing it.

 

The deck is about 12-15 inches above grade. The deck is built off the back (west facing) side of the house and is almost half the length of the existing (house) foundation. Next to the deck is an 8'X12'concrete slab, and then a concrete bulkhead. I know that the wind would cause heating issues and I have thought about closing it off, but I think in order to do that right I would need to build a wall underneath it and go down below the frost line. Right now I have a lattice work around the base and you can see where the ground has changed over the years and caused the framed lattice panels to bulge out.