# Insulating the floor of a prebuilt shed?



## zuren (Feb 13, 2015)

As we continue to contemplate adding a shed to our property to serve as office space for both my wife and myself, I've been looking at pre-built sheds and some of the options places offer for customizing. Since this is going to be a climate controlled structure that sits on 4x4 runners, I thought an insulated floor would be a good move. However, once I add that option to a custom builder tool, it adds $1000 to the cost of a 12'x20' shed. That seems like a lot.

Considering all of the options out there for flooring and foil faced underlayment, would a floor with 1.5-2" of insulation be necessary even in a norther climate? The underlayment I used in a bedroom in our home was foil faced to radiate heat back into the room and had some insulating qualities. If you choose a flooring that helped to insulate (eg, Allure Ultra...rubber), I'm wondering if it is that much of a concern.

Thanks!


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## Fishindude (May 19, 2015)

Could just lay a sheet of your preferred thickness rigid foam over the wood floor, then a new layer of plywood deck over that. Would require some furring strips to screw to, etc.


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## muleskinner2 (Oct 7, 2007)

I just frame it like I would a wall, put down four inches of insulation and cover with two by six T&G. It costs what it costs, but my feet are warm.


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## Bearfootfarm (Jul 13, 2006)

I wouldn't bother to insulate the floor if it's only 4" off the ground.
Just enclose the space so there is no airflow.
Your main heat loss will be through windows and doors.
If you're really worried about cold from underneath, use sheets of styrofoam between the 4X4's


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## melli (May 7, 2016)

zuren said:


> As we continue to contemplate adding a shed to our property to serve as office space for both my wife and myself, I've been looking at pre-built sheds and some of the options places offer for customizing. Since this is going to be a climate controlled structure that sits on 4x4 runners, I thought an insulated floor would be a good move. However, once I add that option to a custom builder tool, it adds $1000 to the cost of a 12'x20' shed. That seems like a lot.
> 
> Considering all of the options out there for flooring and foil faced underlayment, would a floor with 1.5-2" of insulation be necessary even in a norther climate? The underlayment I used in a bedroom in our home was foil faced to radiate heat back into the room and had some insulating qualities. If you choose a flooring that helped to insulate (eg, Allure Ultra...rubber), I'm wondering if it is that much of a concern.
> 
> Thanks!


For your locale, I would think having an insulated floor be top of mind. I could see skimping on that if your shed was a workshop, and one would be wearing outdoor gear, but in an office environment? 
My winters are milder than yours, and folks here have complained about r-28 floors being cold...
While a grand does 'seem' expensive, fixing it after the fact, is a headache and expensive. 
BTW - there is foam one can lay without furring strips (I looked into it when I did a concrete floor). The foam has a low compression % under load. 
Curious what was their insulation method and R-value for the shed floor? Just a quick back of envelope calculation for a 240sqft floor yields about 15 sheets of 2"-2x8 XPS foam, which up here would be about $6-700 in foam alone.


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## big rockpile (Feb 24, 2003)

I would just enclose the bottom during the Winter but open it up some when it gets warmer to let air circulate.

I'm afraid insulating the Floor will be a problem with moisture.

big rockpile


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## Elevenpoint (Nov 17, 2009)

Cheaply built and expensive
Pour a pad and start framing


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## weaselfire (Feb 7, 2018)

Skirt it to the ground, insulate the skirting with rigid foam. If you're not heating/cooling the shed 24/7, it's a non-issue. If you are heating it full time, the dead space is a reasonable insulator.

Jeff


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