Straw bale on wood floor

[Drew]

Hi all,

I have the plans I made, but I have not messed up yet by checking my thinking again.   

We're just finishing the wood floor for our straw bale building.  It's a 18'x24' floor on a post and beam foundation.  The flooring is OSB.  The plan is to lay out two rows of PT 2"x4" around the parimeter (set back 2 inches for the earth plaster) for the first course of bales to rest on.  The PT will be set wide enough to accommodatethe bales (18") and have gravel between the boards.  The boards will have nails sticking up to hold the bales in place.

This is all pretty straight forward and I am good with it.  My question is whether I need some sort of flashing over the edge of the floor (from the OSB to the rim joists) or anything else to accommodate moisture or joining earth plaster to wood.

We are near Oroville, Northern California Central Valley near the foothills.  We have dry summers and moderate winters.

Thanks!

Drew

[Redoverfarm]

Drew off the top of my head I would say yes. But I have never constructed anything with straw.  My common sense says there should be something to shed the water away from the structure whether it be straw or siding.  With that said you could attach a "Z" fashion flashing or opposite 90 deg of sorts to attach to the top of the 2X the allow it to run the width of the 2X then back out to the edge of your subfloor letting it extend enough to turn down to cover the sheeting edge.  Sorry I have it pictured in my head but it gets lost in the translation.

[John Raabe]

If I understand what you have in mind, this might be a suggested detail.

You want a trim board or belly band outside the framing and able to drain water running down the wall. Then you want flashing that will drain your siding out over this trim band. The siding in your case is the plaster.



You need to have flashings or expansion joints where ever you change materials such as from framing to strawbale. Plastering over such joints will likely cause problems as the materials move and settle differently.

Looking at this a bit more, I think I would make the trim board a 2x with a drip stop cut in the bottom and a 45º bevel at the top. The flashing could be bent to this angle and virtually disappear. This would also give the house a belly band wider than the wall and provide a sturdy looking finish at the bottom.

It also provides an honest visual statement of what you are building. A plastered straw bale wall sitting on top of a wood framed floor platform.

[glenn kangiser]

Good plan, I think, John.  I visualized in my head what you drew..for Drew. hmm

[mvk]

I like Johns idea but I have successfully plastered over a wood to foam transition and over a metal drip cap like John's drawing. It was with the old timey plaster I learned to coat block. 3 sand 2 Portland 1 lime over stucco wire. Don't know if it would work with the mud plaster through. I think that I might still go with what John drew because you would have a more solid edge at the bottom and that's where things get smacked into. But if you wanted the full mud look and thought it wood stick here's how I would do it. I would bring my straw out even with my band joist. I would use treated wood for the band and the last joist on the ends. Cover with felt and a metal drip like john pictured. I would then put the stucco wire up a little on the straw. I have studied straw bale a little and the use big wire staples pushed right through the bales, then I would wrap the wire right around underneath the band joist. You could staple it but I like to use deck screws and fender washers. Its pretty malleable stuff so I would kind of bend a dip cap in the wire underneath. then plaster. As I said it might have a brittle edge.

I would probably double up the outside band joist for the same reason I double sill everything maybe not here because it's a utility building but I usually over build like a lot of the folks here.

Buy the way
I have used this stucco wire to critter proof before so far so good but its 3/8" diamond and after reading Don's post I wonder if it isn't to large a opening. maybe we have fat mice I think a coon could go right through it but these are occupied houses. It priced out a little cheaper then hardware cloth and was much easier to work with IMO. down side was 30" width but I used tyvek and then strapped so I had the right spacing.

Another thing I haven't seen the tip here for bending flashing where you cut the form you want in a piece of plywood with a jig saw. you then unroll your metal and re-roll it backwards to kind of break its back. then you wangle it around to get it started through the ply. You nail the ply to a deck or saw horse first. then you get a pair of pliers on it when it's through enough and pull it right through got to keep a straight pull or it will want to cut into the ply. Slicker then snot on a door knob. everyone will think you had store bought the metal. where gloves of course. I'm sure that lots of people know this so if I'm not clear maybe someone else can explain it better.

Mike

[glenn kangiser]

I don't think I ever heard that one before, Mike.

So you must use the thin roll flashing, draw the shape you want on a piece of plywood - then cut the kerf following the lines with the jig saw and pull the metal through the kerf.  The total length of the saw cuts would have to equal the width of the metal plus maybe an 1/8" or so I assume.

So you are just building a home made  human powered shape extruder.  Sounds cool -- I'll have to try it.  Thanks.

[mvk]

Glen
Thats it, but you want it exact size of flashing or it wont track true and don't forget to reverse roll it, first time I did it on my own I forgot to do that and had a B---- I was a Rook and everone got a good laugh on me, watching me struggle and gave me the rass. You would get fired today for permently damaging my physic or some thing.  let me know what you think  it works great on roofs where the flashing is exposed like scotts place. make the angle just a little off so when you nail to side wall it has a little tension lays nice and flat.

Mike

[mvk]

oh no forgot spell check How I do ?
Mike

[ScottA]

Nice idea Mike. I'll have to try that. 

[John Raabe]

Good information Mike. Thanks!

[Drew]

This is great stuff, gents.  Thanks!

I was looking at the vinyl flashing at the Home Depot website (I use it for costing).  I imagine it won't hold the form from the "extrusion" process you mentioned, Mike.  I could tack it down over the 45 degree bevel on the facing board or I could go with the metal and set the angle out a little further from the rim joist like in John's picture.  Hmm.  Now that I say it, it makes more sense to do the second one and let any moisture drip off the metal into the air than roll onto the wood.

Is the vinyl good for anything?

I've doubled up the rim joists already (You'd think wood grew on trees out here).  That facing board is going to have lots of company. 

[MountainDon]

Is the vinyl good for anything?

ACQ PT wood!!  Aluminum and all the standard galvanized stuff makes a poor mix with the ACQ. 

In many applications it's better than all the paint prep you need to do with galvanized.

[Redoverfarm]

Likewise Don. But it is doubtful that he will be able to "break" the vinyle approiately.  He could use a layer of felt paper between the PT and the alum then once he is off the PT lumber and onto the regular OSB it wouldn't matter.  I did that on my termite shield (alum) next to the PT lumber.