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Small Cabin Forum / Cabin Construction / Floor insulation
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brownsburg
Member
# Posted: 9 Oct 2011 09:24
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Hi,

I'm in need of some idea's on how to best insulate the floor of my new 12 x10 cabin. I know that it was an error on my part not to do it during the flooring/joist phase but I need to get over this and come up with a solution. The joist are 12inch on center and the flooring is 6inches off the ground. It is possible for me to get under there to put in rigid foam but I'm not sure how I would get it in super tight to act as a vapor barrier. I cant really get in there with spray foam cans to fill the gaps.

I could also attack this from the top with those 2' x2' prefabricated foam/particleboard subfloor sections. This would be fine for insulation but I'm still a little concerned for the actual underside of the plywood of my floor with rotting.



trollbridge
Member
# Posted: 9 Oct 2011 22:58
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How are you planning on heating your place? Our small cabin(12x16) has no floor insulation and sits low like yours. We have a wood stove in it and I have never once thought the floor was cold and we are in northern Wisconsin.

toyota_mdt_tech
Member
# Posted: 9 Oct 2011 23:19
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Quoting: trollbridge
How are you planning on heating your place? Our small cabin(12x16) has no floor insulation and sits low like yours. We have a wood stove in it and I have never once thought the floor was cold and we are in northern Wisconsin.



I'm with troll bridge, skip it, put down a nice vapor barrier through.
One other option, remove all the walls, frame in some 2X6 16" OC on top of the floor, sheet it again with insulation under it. Then set walls on top of that. With a few buddys, you all can lift those studded walls if you are careful. Otherwise, I wouldnt worry about it but you want that vapor barrier down.

brownsburg
Member
# Posted: 11 Oct 2011 17:52
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Sorry, I should have mentioned that the cabin is finished, so removing the walls is not an option.

It will be a 1500 w convection baseboard heater for the winter. I don't need to keep it at house temperature, just warm enough to read a book under a blanket or have some camp outs with my son.

How would I go about adding a vapor barrier at this point? Could I use my roll of 10' Tyvek that I have left over?



Montanan
Member
# Posted: 12 Oct 2011 13:16
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We have a similar issue and have exposed plywood subfloor underneath. Ours sits slightly higher off the ground, but not much.

Quoting: toyota_mdt_tech
Otherwise, I wouldnt worry about it but you want that vapor barrier down.


Do you mean a vapor barrier underneath the cabin, or between the OSB and the finished flooring? Thanks!

trollbridge
Member
# Posted: 12 Oct 2011 15:27
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Montanan,
I bet that you maybe wouldn't notice a difference between insulation or no insulation also. You will have sooo much snow that the wind isn't going to get under your cabin cause the snow around it will act as your insulation. I am curious though about the vapor barrier so I will be watching to see what toyota has to say. Our main cabin we did insulate the floor cause it sits up off the ground quite a bit. It was very easy to do before the subfloor went on. Did you have snow this weekend at your place?

dvgchef
Member
# Posted: 12 Oct 2011 16:11
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brownsburg
Great cabin! Sounds like you have some good answers, good luck deciding what to do. I want to compliment you on the cabin - do you have anymore pics?

brownsburg
Member
# Posted: 12 Oct 2011 18:15
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dvgchef, thanks for the compliments.

Montanan, I too would like to know where the vapor barrier is suggested.

I can't see it going straight across the bottom of the joist, maybe up/along and then back down, but that would be crazy. I'd rather spend my time under there with rigid foam. : )

Or, I could coat the plywood from the underside with that green wood preservative that stinks. Would that do it? I mean, keep it from rotting.

Upon preparation of the ground for the cement blocks, I laid down landscaping cloth, then 1/4inch wire mesh, and then 2" of large 3/4" clean gravel. All to keep the moles and field mice or ground hogs from living under there. I know that it is open to activity all the way around but I figured that they would prefer ground access.

Thanks

brownsburg
Member
# Posted: 21 Oct 2011 19:26
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Okay,

shorter this time...

Where would the vapor barrier go if the cabin is already finished?

Thanks

MtnDon
Member
# Posted: 21 Oct 2011 20:06
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In a cold climate the vapor barrier goes on the warm side of the insulation.

With a floor sheathed with T&G OSB or plywood as sub floor, the sub floor with all its glue acts as a pretty good vapor barrier. If the sub floor sheathing was not T&G but is well nailed it is still a pretty good vapor barrier.

For walls or ceiling that is already insulated and the inside surfaces completed with drywall, use two coats of PVA primer before the finish coat of paint. If its wood paneled a good acrylic or oil based clear coat will accomplish much the same. Of course if there are lots of joints between boards and there is no plastic or kraft paper under it that's not a good situation..

Hope that helps.

trollbridge
Member
# Posted: 22 Oct 2011 08:44
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Quoting: MtnDon
With a floor sheathed with T&G OSB or plywood as sub floor, the sub floor with all its glue acts as a pretty good vapor barrier. If the sub floor sheathing was not T&G but is well nailed it is still a pretty good vapor barrier.


Thank you- that makes sense and is good to know!

brownsburg
Member
# Posted: 22 Oct 2011 08:45
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Thanks.

The floor is actually 3/4 finished (not knots) plywood, not T&G.

Linoleum tiles are going to be glue down directly on top of this plywood. Should I be concerned that the temp. difference between the inside and outside will cause them to pop off?

Since the plywood is not PT, should I be concerned about it rotting? I would want this to last 20-25 years, it's not a garden shed.

trollbridge
Member
# Posted: 22 Oct 2011 08:48
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You should put down a layer of underlayment over your plywood before your linoleum tiles go on unless your plywood is extremely smooth.

trollbridge
Member
# Posted: 22 Oct 2011 09:31
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I'll ask my husband about the glue and temp. differences. He is a flooring contractor. I know the floor should be very smooth and I also know we glued the sheet vinyl in our bunkhouse and it has done great. Tiles are a little different though-you'll really want them to stick well.

Your cabin looks nice. How much of the inside do you have finished so far?

trollbridge
Member
# Posted: 22 Oct 2011 15:37
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My husband says obviously you need NO movement in the floor and he is assuming you are using vinyl tiles or vinyl composite tile since Linoleum is an old term referring to a type of floor that he doesn't think is made anymore. It used linseed oil.

Check with the manufacturer and use the proper glue. It is probably clear thinset adhesive. Use a fine notched trowel or even a paint roller to apply. First snap chalk lines. Apply glue and let sit for 45 minutes to an hour until it turns clear and you see your chalk lines. Don't forget to glue yourself out of the room and work in a stair step fashion (off of your chalk line). Work diagonally across the room from your door to the opposite wall. Does that make sense? In other words, don't lay one whole row then another whole row and another.

If your plywood is sanded and joints are patched and level you don't have to use underlayment. Check with the manufacturer for sure about the unheated cabin/glue or double check with the store you are buying it from. His thoughts are that you will have no problem with them holding-but no movement is crucial (especially when the floor is cold).

Good luck!

MtnDon
Member
# Posted: 22 Oct 2011 18:28
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Can't pass on any info about vinyl, but we have ceramic tile over cement backer board over OSB and have no problems of any sort with the cabin goping through repeated heat - freeze cycles over a few winters now.

trollbridge
Member
# Posted: 22 Oct 2011 19:32
Reply 


Yeah, with ceramic tiles the biggest problem would be too much bounce in the floor causing them to crack.

MtnDon
Member
# Posted: 22 Oct 2011 19:57
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Just keep the deflection to L/360 or less

check this calculator

trollbridge
Member
# Posted: 22 Oct 2011 22:35
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Very handy calculator!!! It is so easy to use-wish all span type charts were as nice! Thanks for posting it.

brownsburg
Member
# Posted: 23 Oct 2011 18:05 - Edited by: brownsburg
Reply 


Yes, thank you for the deflection calculator.
Screen_shot_201110.png
Screen_shot_201110.png


MtnDon
Member
# Posted: 23 Oct 2011 18:52
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Yeah, ain't technology wonderful!

toyota_mdt_tech
Member
# Posted: 25 Oct 2011 21:27
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Quoting: Montanan
Do you mean a vapor barrier underneath the cabin, or between the OSB and the finished flooring? Thanks!


On the earthen ground under the cabin floor.

Alaska Jon
# Posted: 27 Oct 2011 22:21
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I have a insulated and heated 10 x 12 shed that I heat with a electric radiator type heater.
The floor is not insulated but sits within ten inches of the ground. I store my paints and glues there year round. Temp never goes lower then 68 even if the outside temp is -35 F
Don't worry about the insulation on the floor just insulate the roof and walls well.

Anonymous
# Posted: 23 Nov 2011 17:35
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Wow,

Thanks Troll. This is great info that I somehow missed my last time through this post.

The cabin doesn't even have paneling up at this point. Winters here, so I 'll finish up insulating the walls, apply paneling, baseboard heater etc. I'll glue down the flooring only in the late spring when the temps' are back up around 15 cel.

Thanks again

Anonymous
# Posted: 23 Nov 2011 18:09
Reply 


Wow,

Thanks Troll. This is great info that I somehow missed my last time through this post.

The cabin doesn't even have paneling up at this point. Winters here, so I 'll finish up insulating the walls, apply paneling, baseboard heater etc. I'll glue down the flooring only in the late spring when the temps' are back up around 15 cel.

Thanks again

builder
# Posted: 1 May 2012 18:27
Reply 


try using styrofoam 1" and then placing another layer of 3/8 plywood on top of the styrofoam and you have a nice warm floor. Thats what I have done and know others who have done that.

Sustainusfarm
Member
# Posted: 6 May 2012 11:08
Reply 


I insulated around the outside perimeter with 2" foam...works great and keeps the citters out from underneath the cabin....I see that building stores now have a stucco-like face 2" foam board that measures 2'x4' that you can insulate the perimeter with...sink it in the ground and attach to the outside of your foundation...done!

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