Work Shop

I wanted to get ya'lls thoughts on this. I built a 24x36' shop concrete floor w/plastic under it. Light poles and 2x material construction with metal roof and walls.I want to finish the inside and this is how I was going to do it. Because its metal I have a codensation issue so I was going to staple plastic sheathing inside against the metal for a vapor barrier. Then insulate and put up 1/4"x4'x8' osb for ceiling and walls.I was thinking about running the electrical in conduit on the outside of the walls and ceiling for easy access if I needed to change anything.I built this by myself with 2 of my tractors pulleys and ropes.It also has a 24'x 32' lean to on one side.I built a pole barn 36'x 40'about 20'at the top with the tractors to.They make good helpers don't they. Thanks for you time and thoughts.

i know its not really a do it yourself kinda deal but get spray on insulation and be done with it...you will never get a good seal with plastic with the metal already installed...will save you a ton of headaches in the future.

Metal is a symptom not the problem. It just makes a surface for moisture to condense on, in the right climatic conditions. You don't say what part of the world you are in, except for the y'all, but here in the northeast, code calls for vapor barrier to be on the INSIDE of the insulation, otherwise the vapor will condense into water drops as it penetrates the insulation to where the temp is down to dew point. the OSB is usually considered too combustible for a wall in that sort of building except where occupancy makes it desirable. You may want to consider sheet rock for the ceiling and upper part of the walls.

If I understand correctly, you propose to have your vapor barrier on the outside of your insulation (the cold side). That's probably not wise because the moisture in the shop will move through the insulation and condense between the vapor barrier and the insulation, probably making it wet enough to eventually fail and cause moisture problems. It would probably work if you put the vapor barrier on the warm side of the insulation. That's how they do it in houses, and that's why they do it that way.

I'm near Memphis Tennessee. So it would be better to put the insulation in the wall then put the plastic over it then the wall board over the plastic? I thought if the plastic was against the metal that would keep the insulation from gatting wet. Its not a bad problem in the closed in part.I set on my trailer under the lean to and deer hunt and it looks like rain sometimes coming from the ceiling.Thanks.

I agree, It seems high but the spray on foam is your best bet, my son is spraying his entire building,42X72 12 ft high. it sure is high 1.70 a sq ft. You won't believe the difference.

generally you want your vapor barrier to the heated(or conditioned) side,normally the inside,of your building.Though many folks use house wrap on the outside under siding or brick, most of these products are breathable to allow moisture to evaporate.A barrier is just that,if you put a barrier over the metal outside, condensation will just build up on inside of it .This in turn will soak into your insulation,and you will have mold and rotting problems in your walls and ceiling over time since moisture cant escape.if you DO put something against tin , make sure its breathable to allow condensation to wick away.We used to use tar paper or roofing felt,contrary to most beliefs it is breathable .Vapor barrier is strictly to protect the INSULATION from moisture,since moisture causes it to lose its insulating values.As youve found out condensation will form on the warmer surface, if it cant get out ,your in reality better off with no vapor barrier at all.simple way to tell if you need vapor barrier, and where, is to watch where moisture forms ,if it forms inside ,moisture is coming from inside and thats where you need a barrier.if its forming outside,and some places it will,you need it outside.oddly you will find little about vapor barriers in most building codes (that ive seen anyway).tendancy is to not use any if not required so ive heard.and this may be your best bet .give the inside walls 3-4 coats of oil based paint and it will serve. .1/4"osb might not be thick enough for the ceiling,it will tend to bow and sag on you over time i would think just from its own weight.

also some are advocating the foam insulation ,and it does really work well,but the reason it does is it doesnt absorb moisture like normal cellulose,or fiberglass batt insulation does. but i find it hard to work around if you need to get back in walls for some reason,say to run a water ,air,or electric line.I like it ,have it in one of our buildings ,but make sure youve got all the lines where you think you will want them before you have it sprayed.

In our "pole barn" we built stud walls between the posts. Insulated w/ fiberglass insulation.

Walls covered with OSB.. But we went with 7/16"

Ceiling covered with barn tin siding, and blown insulation above..

However, we have a shingled roof, and that makes a little difference..

Our old shop had drywall on the ceiling.. it started to sag and fall down.

If I had it to do again, and had money to spend, I'd either have block/poured wall up about 2 feet, or tin from the floor up 2-4 feet, that way I could "evacuate" the contents, and take the pressure washer to the floor once a year. And depending on how you laid the tin on the walls, it would make a nice "backsplash" for the work benches.

Brad

You left alot of details outm but think you are putting the vapor barrior on the wrong side? You want outside to breathe?

--->Paul

thats right barrier to the inside ,heres how it works, heat travels from hot to cold(ALWAYS).when heat goes through walls (and it will) it picks up moisture inside insulation and since colder air doesnt hold moisture as well it it takes it outside where it evaporates. if it cant get through a vapor barrier it will build up and cause mold ,warping of walls ,rot and all the other bad things.one reason tin has ridges ,besides adding strength is to allow air circulation to avoid moisture buildup.since your air conditioner ,if you have one in your shop in summer removes moisture in the form of condensate,it dries the inside of building and vapor barrier stops moisture from building up on inside walls in summer.this does cause insulation to hold more moisture,but since the only way it can go is out,and since the cooler surface does not hold moisture it dries quickly just from simple air flow. those folks who say they have sheetrock warping problems probably have NO vapor barrier.what this does is cause moisture to build up inside sheetrock simply because moisture is always there,traveling one way or the other, especially if you are heating inside. in a real bad case, you cant even paint a wall!.moisture will go one way during day and the other way at night. you paint a wall during day,come back in the morning and paint has simply washed off walls onto floor.

Put up a new building 2 years ago, put 2" of closed cell spray foam all over the inside. Last winter when it stayed below zero for several days, the inside of the building never dropped below 40 degrees. With 2 inches you have no problem with wires or water pipes. If the money holds out next summer I will put it in my house addition.
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2 years ago I had built a 30x40x10 pole barn. The price was the same, metal roof or trusses on 2 ft, 1/2 osb, 35 year shingles, ridge vent and 1 ft vented overhang. I went with shingles and have yet to have a condensation problems. I've seen some pole barns where they removed the metal and went with shingles because of condensation. I don't think I'll ever worry about a snow load either.

You better make sure that foam you want to use is fireproof.

I have conduit exposed on the inside walls. Easy to modify or add to at a later date. Pic's available if you like.

Condensation will go away if you move the air. Gable vents and you will not have a moister problem.