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Late last fall, we had a sunroom built on our nhouse, and we're trying to determine what type of flooring should be installed. We live in Winnipeg, Manitoba, Canada, so the climate will definitely be a factor.

The flooring is plywood, with metal flashing around the outside edge at the walls.

In January/February, the temperature can reach -35C (-31F). In July/August, the temperature can reach +35C (95F). The sunroom is south-facing, with all glass/aluminum walls, so the air temperature inside during summer will be higher than that. In winter, the sun won't have any significant moderating effect on the temperature.

Compounding this, we have a dog that we let out into the back yard every day, so we walk through the sunroom two or three times every day, winter or summer. In winter, this lets a lot of moisture into the sunroom, which condenses on the windows. As we get closer to spring, the moisture melts and pools at the edges of the sunroom, and wicks onto the plywood if I don't mop it up quickly enough.

We have been told that some flooring types won't be suitable (linoleum and vinyl, I think) because they get brittle in our winter temperatures. We were expecting to have to use some outside carpet, but one flooring company told us we could use laminate flooring. I'm getting a sense that the contractor is a bit of an amateur, though, and I've read that laminate flooring contracts in the cold, so I would expect it to shift as we walk on it.

Can someone please recommend types of flooring that may be suitable for our conditions? I plan to have whatever we choose professionally installed (I'm not very handy).

To clarify, the sunroom is a raised structure with insulation in the floor and ceiling. It is an unheated space, and with the temperatures we get in the winter, no amount of insulation will help an unheated space in January. The structure seems quite secure, with teleposts of some kind on top of concrete footings.

EDIT: Not enough reputation to comment on my own question. My installation does not have any sort of pan. The walls are mostly glass with a metal frame, which stands on metal flashing. The flashing extends 5" from the glass/metal walls, and the remainder of the floor is plywood. Since we open the door from the kitchen several times a day to let the dog in and out, the air in the sunroom, which would normally be very dry in the winter, ends up having a lot of moisture in it, which condenses and freezes. In the spring, as the sun becomes more intense, the condensation melts and pools at the base of the wall. I mop it up every day to reduce the amount that can condense that evening, but a couple of times it has reached the plywood before I got home. My thought was to install whatever flooring type is best, then put a barrier of some sort (metal or plastic edging), then add a bead of silicone along the entire edge, to force the water to stay on the flashing until I can mop it up.

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  • How is the moisture getting onto the floor in the first place? Sunroom/greenhouses I built had a pan where it contained all the condensation so it would not go out onto a floor. This is asking for the plywood to rot, should it go under the sill plate and set. – Jack May 7 '15 at 21:48
  • Please add a picture to the post to help understand the arrangement you have. It sounds like the flashing extends to the inside of the sunroom by a good margin, but enough moisture puddles so it runs off the flashing that is laying flat and goes onto the floor. If that is the case the pan needs to be turned up and the corners sealed. The biggest issue will be getting the condensate out. Typically there is a wick cord so it soaks up the water and gives it a chance to dry out through the wick. Or there is a weep hole system to allow the water to escape to the outside that way. – Jack May 8 '15 at 2:28
  • If whatever you do use is dark in colour it will warm from sun. This will help dry the floor. There may be merit in running a dehumidifier in the room. Most have a thermal shutoff. It would run whenever the room is above freezing. A strip of absorbant material in chunks that can be easily moved from the inner door to the outer door will catch most of the wet from the dogs. Bring it in every couple days to dry it. Or install an exhaust fan. Power it with a solar cell. It runs when the sun is shining and the outside temp is relatively warm. – Sherwood Botsford Nov 2 '17 at 16:55
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Your best option is sheet vinyl. Next to that would be tile or concrete.

Most other flooring has seams which will eventually leak. Yes, you can place vinyl tiles, or even laminate flooring, if you appropriately glue/seal all the seams. Eventually the seams will leak, and in the case of laminate surface scratches must be sealed immediately to avoid damage to the laminate below the waterproof surface.

A single sheet, if possible, will provide continuous leak protection across the entire floor surface. If it's too wide for a single sheet, then a single seam is easier to keep sealed than the multiple seams found in other flooring choices.

Tile and concrete are both good options as well. Regular maintenance and upkeep will keep them in good waterproof operation for the life of the house, while vinyl will need to be replaced every decade or two.

Even though it's designed to be an unheated space, you should consider adding a vapor barrier and insulation to the flooring area. This will reduce the likelihood of later rotting or water condensation.

Keep in mind that outdoor carpet requires a sealed or well-draining surface. Your current plywood would have to be treated and sealed for the outdoor carpeting to be useful. The carpeting alone won't prevent damage to the subfloor - it will only avoid damage itself when exposed to water.

In your situation you need to protect both the flooring and the subfloor.

Regarding the cold temperatures, newer vinyl floors are much more flexible and resilient even in the fact of extreme cold weather. You'll need to specify that both the flooring and the adhesive be tolerant to freeze-thaw cycles.

Be certain that your subfloor is substantial and secure. Cracking occurs where stresses increase significantly on one area of the floor. As long as the vinyl is well-adhered to the subfloor, and the subfloor is relatively stable, then the stresses from expansion and contraction will be spread evenly across the entire surface. While these forces are large, they won't overcome the strength of the vinyl. If the subfloor develops a large gap, then the stresses in the vinyl would be greater around that gap and that's where a tear might start.

So your flooring really starts with a good, stable, strong subfloor. What you put on top, then, will be fine as long as it can deal with the water exposure.

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  • I send the tile/concrete suggestion – warren May 12 '15 at 20:48
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Just been researching the same thing, with same requirements, and found some good information. Sorry that it's two years after the original question.

Most laminate flooring I've seen - vinyl, wood or composite - has indoor office/home temperature range. Some will go down to freezing (0C/32F) or lower. If there's no rating, assume it's normal household/office.

For waterproof, vinyl is a frequently mentioned. Again, check the spec sheets. If it doesn't say so, it's not waterproof. I've seen some crappy vinyl stuff in stores, where even the samples on the shelf - not being walked on! - have the top layer peeling back like wallpaper. And water... I've seen the horrid effects of a window left open when it's raining. Only takes one soaking to ruin it.

Dogs and people walking across it from outside mean you want some decent abrasion resistance. That's the primary meaning of the AC ratings with the higher the AC (usually topping out at AC6) the better. Higher number usually corresponds to longer warranty.

Temperature range will expand/contract the material. You'll be looking at a floating floor (i.e. not nailed or glued), which is typical for laminates. It's expected that you will leave a gap at the walls to accommodate this, with the gap covered by leaving some tuck space under your drywall and/or using an appropriately thick baseboard and quarter-round.

Yes, you can get something to meet all these conditions. I've seen some very nice waterproof, wood-look, click vinyl laminate that's temperature rated from -40C to +45C (-40F to +110F), with an AC6+ rating.

Whatever you do, you need to fix your moisture problem. Some well-placed ventilation should do it - just like an attic, where you put roof vents above the insulation. It's either that, or properly insulate the room - which may not be a option because of the glass.

The moisture might not affect the flooring you select, but will probably get through to the underfloor and rot it out.

If you built the room yourself... well, live and learn. If a contractor build it and didn't tell you about this... do not recommend the contract to anyone you like.

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From what I have read it sounds to me that you have a bigger issue than just flooring. It looks to me that you don't have thermal insulation on both floor and walls (or at least at one of those); or if you do have some insulation it is not thick enough. So for start you should put some insulation. Now when it comes to flooring I would suggest polyurethane self-leveling floors. I think you will find them to be suitable for this situation. But, before self-leveling floor you should pour cement screed. Make sure that it is reinforced because these floors are really strong and sometimes can pull up screed.

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You could use vinyl but you would have to use a 2 part epoxy adhesive if you go onto Altro web site and speak to there technical team ask them questions they will tell you what to do I'm from England but I fit flooring for a living and we have to do flooring in walkin freezers sometimes and we fit Altro 2.5mm anti slip with Altro A19 epoxy adhesive if they are any joints they can be heat welded so no leaks the adhesive also works under hot conditions also

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  • Pushing a brand is not favorable here on Stack Exchange. Perhaps you could edit your response; instead of saying Altro A19, why not say 2 part polyurethane floor adhesive? Technically it's not an epoxy, although I can certainly understand why most people would assume it was. Also, since you are pushing for 2 part polyurethane floor adhesive, you should explain why someone must it as opposed to other vinyl floor adhesives, or perhaps why being in a sun room makes 2 part polyurethane floor adhesive important. – Ben Welborn May 20 '16 at 18:07

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