[Greenbuilding] building floor on top of rigid foam... (basement/garage retrofit)

[JOHN SALMEN]

I missed this thread somehow. I can testify that putting a floor directly on
eps foam is a great system. I have done this in a number of renovations, new
homes and a school.  The basic spec. is rigid eps board (minimum 4”)  on a
level surface w/ t&g ply sheathing laminated directly to the foam with a
suitable adhesive. That is it.  The level surface does not have to be
concrete – it can be a granular base (sand). 

 

The real point of this approach is to avoid the use of concrete or in the
case of insulating on existing concrete to isolate from moisture and to
minimize the use of unnecessary materials. 

 

As for materials the ‘suitable adhesive’ is generally specified as a
polyurethane foam adhesive (enerbond or equiv.). If the finished floor is to
be ¾” solid wood nailed -  I specify a min. 5/8” t&g ply sheathing. If it is
tile I generally specify either a thickset mortar directly on the foam
(w/reinf.) or an additional layer of ½” ply laminated and fastened @ 3” o.c.
I’ve found that most contractors get the concept pretty quickly but the
trick is that in putting down the ply it needs to be flattened and weighted
down while the adhesive sets (concrete block, buckets with sand, etc...)

 

For your application I would eliminate any subfloor wood framing (sleepers).
Waste of time and material. eps boards can be ordered cut to the thickness
needed for the finished product. Using foam on an existing slab it is nice
to have additional thickness – 5-6” foam can span any deflections or defects
in the concrete. I would spot adhere the foam to the concrete.  

 

Essentially the finished floor (eps and ply) is a weight bearing floating
floor that can carry standard interior partition loads well. It is a pretty
nice floor.

 

From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of RT
Sent: April 16, 2011 3:59 PM
To: satjiwan at alumni.brandeis.edu; Green Building
Subject: Re: [Greenbuilding] building floor on top of rigid foam...
(basement/garage retrofit)

 

On Sat, 16 Apr 2011 15:53:26 -0400, sat jiwan ikle-khalsa 
<satjiwan_khalsa at hotmail.com> wrote:
>
> we're aiming for about R20 floor insulation (rough passiv haus goal for 
> our region - Mid Atlantic USA).  we're thinking to put 2 layers or two 
> inch rigid foam on top of the existing slab then build a floor with 2x 
> framing members sufficient to bring the height up so 3/4" plywood and 
> carpet on top will meet the other room's height.
>
> would Roxul rigid foam work? is it specified for load applications?

My first question would be:

"Why is (steenking,off-gassing, allergen-magnet) "carpet" even being 
mentioned  ?"

My second question would be:

"Why would one choose to use extruded polystyrene in that situation

My third question would be:

"Why bother with the wood framing ?
                               
(There is no such thing as "Roxul rigid foam" as far as I am aware.)

If I were doing the project, I'd use the less costly and more 
enviro-friendly expanded polystyrene (EPS) rather than the extruded (XPS) 
and leave out the wood framing/ carpet altogether and just cast a 2.5" to 
3" thick concrete slab on top of the EPS, possibly colouring/stamping the 
concrete or laying stone or porcelain tile over if for some reason the 
skills are lacking to produce good quality concrete.

This of course allows one the option of installing hydronic heating in the 
slab if necessary (ie if taking advantage of direct gains isn't possible).



--
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  C A >
(manually winnow the chaff from my edress if you hit REPLY)

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