External insulation support

[Rait]

Hello, i have some trouble figuring out good way to attach insulation (blown cellulose) bottom support to a sill. Sill is 8x10 inch. Insulation support is 2x8 inch.

I have post foundation to keep the concrete usage down. Best i could come up is use simpson ties to attach the insulation support to a sill. The external cladding (wood) and wind break will also attach to this, so there is lot of weight (i havent done the calculations on how many ties i need yet) to hold up.

Is there a better way (while not using more concrete) to attach the insulation-cladding support or does this seems like a way to go?

Thank you



 

[Roger Nair]

The idea I would pursue will be concerned with the exterior wall support, the walls creates the void and insulation fills the void.  If the wall has 2 x 8 studs, then use a 12 Hor x 10 Ver sill with the studs notched around the sill, using the protruding sill as a ledger and the considerable weight of walls directly bears wood to wood. 

[Brian_Weekley]

Try doing some searches on the "Larson truss system".



I think you'll find some examples of supports that hang on the outside of the walls and are used for cellulose.

[Ljohnsaw]

Hello, i have some trouble figuring out good way to attach insulation (blown cellulose) bottom support to a sill. Sill is 8x10 inch. Insulation support is 2x8 inch.

<<snip>>

Why not just build your walls directly on the 8x10 sills?

[shinnlinger]

Or cantilever your floor?   If you look in my gallery you can see I built my frame 19" inside the edge because I was originally going to do a straw bale wrap.

[Rait]

Thanks for advice. Nice house Shinnlinger but yours is slab, mine will be concrete posts.

I do not want to go above 8x10 mainly to make raising not so heavy lift exercise. If i build walls over floor joist on sills, i would lose another 10 inches in height (want to keep overall height down while still have headroom inside Also where possible, i dont want the internal structure to portrude insulation layer.

Larsen truss was what i was planning to use, but i had not seen the sketch Brian attached (the ones i have seen have one stud supported on foundation), i think that is the way to go! As Larsen trusses are not structural, i guess the spacing is dictated by windbreak and sheating attachment requirements only?

[Roger Nair]

Rait, I want to offer a caution concerning the adapted use of details pulled from a system without a full design consideration.  The Larsen Truss System is a double wall system, taking 2 x 2's and plywood gusset details does not make a Larsen truss.  Without the continuous inner structural wall support, the very minimal "truss" becomes a more risky structural element.  I believe for a long duration service life, use of more robust details and less dependence on a frame hanging on nails is needed.

[JimXJ2000]

 
I wanted to have my insulation layer outside of the timber frame (and not use SIPs).  To make a similar "shelf" as we called it, I cantilevered a 2X8 off the top of the rim joist (stick framed first floor deck- but you might be able to use the bottom beam in a similar manner) with another 2X8, beveled at 45 degrees both edges to support the cantilevered 2x8.  This was jointed with nails, construction adhesive and lag bolts. 
On top of this sits a 2X4 stick framed shear wall that is lag bolted to the barn frame.  Outside is this is a layer of 3 inch think polyiso foam, then ZIP sheathing...strapping for an air space then old barn board.  The 2X4 wall also holds all the wiring (done just like a stick frame house) and fiberglass insulation, and works to attach the drywall to. 

Not the easiest process (more time consuming, but DIY possible), but it stiffens the frame, makes wiring easy, good insulation.  bolting the 2x4 sections to the timber frame keeps the weight of the walls and insulation off the "shelf" at the sill and into the timber frame posts. 

First pictures shows the shelf, second the 2x4 wall, third the sheathing (frame stiffness) layer, insulation and ZIP sheathing layer. 




 



  




 

[Rait]

I believe for a long duration service life, use of more robust details and less dependence on a frame hanging on nails is needed.

I hear you, then again, i spoke to engineer and he showed me plans where external insulation is basically supported by metal corner brackets (though it used lagbolt in addition to screws). Ill try to speak down the larsen trusses to him, if he still says i can use them, then i consider it decided, just that for ledger (not sure if its right term) board i would have some lagbolts in addition to nails.

One of the problems i have is that american type of timber framing is not traditional here so not so much knowhow.

Anyways, thanks a bunch for feedback!

[shinnlinger]

 "Nice house Shinnlinger but yours is slab, mine will be concrete posts."

Thanks, but my house has a full basement with stem walls, I would not consider it slab construction.  I also think you could cantilever over your posts or put floor beams like I did over your concrete posts and set your framing posts back from the edge to create your shelf.

Dave