Sunroom reno advice and help from a contractor (somewhat long )

[Silverwood]

I have what I call a sunroom.  It's a basic 2x4 structure with plywood floor over cement piles in the ground. It has a sloped roof. Basically like a screened porch except it has windows. It  isn't insulated and I find it dumb cause it gets either really hot or cold and isn't much use to me that way.

The old owners drywalled  the inside and put green outdoor carpet down. Then painted 3 walls and wallpapered the 4th. The 4th wall had the original wood siding underneath it.  The drywall had gone moldy so I ripped it down.

I wanted to covert it to a 4 season room so I started tearing down the rest of the drywall and that's when I found out there is water damage to the plywood underneath the  south windows. There is also rot on the outside of one window ledge on the north side.

I'm guessing that you take off the siding and replace the rotten plywood. Then cover with tyvex and reside.  However I have never done this kind of advanced work before.  I'm not sure if it would be better to tear the whole thing down. All the windows are old and the roof should be replaced and I'd like to move the door to aline with the garage door.   

But that's sounds expensive. Is it possible to do one wall at a time? Would it be just the wood that needs replacing and maybe some window flashing is needed? Where do I start? Can it be done in peices? Some now and the rest next year.I do plan on calling a few guys and getting quotes but I thought I should at least know a little about what I'm asking,before then. I think if I got the basic structure ready I could easily insulate it. Siding seems somewhat easy. I do YouTube a lot.

[sokoloff]

In small jobs like that, fixing is often more work than tearing out and starting over, especially if the original workmanship is questionable.

If you try to do it a wall at a time, you'll go nuts. Go big and git 'er done, IMO. Plan the electrical, RG-6 (cable/coax), Cat-6 (ethernet/phone) that you'll want and build it right.

[BudgetSlasher]

In small jobs like that, fixing is often more work than tearing out and starting over, especially if the original workmanship is questionable.

If you try to do it a wall at a time, you'll go nuts. Go big and git 'er done, IMO. Plan the electrical, RG-6 (cable/coax), Cat-6 (ethernet/phone) that you'll want and build it right.

I am inclined to agree with you. Especially where there is water intrusion in 2-3 walls of 4 walls. . . Not to mention it appears that he is in the early stages of finding all of the problems, I would anticipate the mushroom factor to appear shortly.

Seeing that the original wood siding is still on the (previous) exterior of the house, I would want to make sure that the room had been correctly connected to the house flashed correctly.

To the original question, yes you get at the plywood from the exterior, the apply your house wrap (or use zip panels and be done with it) flash and reinstall the siding; at least that is what I remember for helping on similar projects when I was much younger. 

Before you put a lot of effort into this project, I want to address your original complaint; it gets too hot or too cold. I have an insulated sunroom on this house with double glazed argon filled window facing the exterior on 2 sides and the same style of windows and doors facing the interior of the house, it even has its own heat register (no A/C here). In the winter it is still slightly colder than the rest of the house, but in the summer . . . oh boy we close it off from the house until it is cool enough outside to open the windows for the night and by then it is 15-20 degrees warmer than the rest of the house.

There are 2 items at play for us. First, a lot of windows with a good bit of sun results in a high thermal gains from the sunlight entering (something you want in the cold times, but not the warm ones.)  Second, if I recall correctly an energy star window has has an R-value of around 3 and maybe up to 5, older and single pane windows will drop significantly (To put that in perspective lets look at this chart https://www.archtoolbox.com/materials-systems/thermal-moisture-protection/rvalues.html If you have siding, 1/2" plywood, an air gap greater than 1/2", and 1/2" dry wall on the interior you may already be looking at R-2.68 or so.) So insulating the wall cavities will improve your situation, but if you have a lot of windows you may still be looking at temperatures that are more extreme than you would like.

[Goldielocks]

In small jobs like that, fixing is often more work than tearing out and starting over, especially if the original workmanship is questionable.

If you try to do it a wall at a time, you'll go nuts. Go big and git 'er done, IMO. Plan the electrical, RG-6 (cable/coax), Cat-6 (ethernet/phone) that you'll want and build it right.

+1

Especially where you want to go from a 3 season to 4 season.  you will need to create the proper connection, vapour barriers and insulation, maybe even double check foundations (those 3 season porches and such were often built to enclose a deck, which has minimal foundation).     What about drainage away from it?

Maybe yours is better than most, but from your description, there is a whole lot going wrong with it over the years.

[RetiredAt63]

If those cement tubes are from Sono tubes and go below frost line, you have a good foundation.  My parents built a sun room, same foundation, but then it was full attached to the house, with heating and electricity.  The floor was fully insulated and had the proper vapour barrier.  Same with the walls, built as outside (i.e. vapour barrier and insulation) walls.  It was comfortable year round.  You may be better (as others have said) to rip it out and start from scratch.