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Attaching the 8x8 sill directly to the slab foundation or a sill plate?

Started by Malloy5944, November 21, 2019, 09:20:34 AM

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Malloy5944

Hello,
I've been reading about Timber Framing for almost two years now on forums (mainly this one) and books. I am wanting to build Jack Sobon's garden shed but I require the floor to be a concrete slab. I want to turn this into my blacksmith shop with out risking burning the entire building down. I have searched the forum for months now and can't seem to find the answer I am looking for so I figured I would ask. 

Do I still lay the 8x8 logs down as a sill and anchor that to the concrete or do I anchor a 2x8 pressure treated sill plate to the slab and lay the 8x8 logs horizontally on top of it. Or do I just skip all that and anchor the posts vertically into the slab like a pole barn? I would be using Ice and water shield as a moisture barrier. 

I really like the look of the 8x8 "sill" as it gives it a more uniform look in my eyes but also uses more timber. 

In my head I am thinking of welding a vertical steel plate to a horizontal steel plate and attaching the horizontal portion to the slab with J-bolts embedded in the concrete. then having the vertical portion insert into the 8x8 about half way and running a bolt through it. I would plug both ends with a dowel and hide the bolt completely.  

Brad_bb

One big lesson I've learned is to NOT wet set any anchors in concrete if I can help it.  No matter what you do, they never end up in exactly the position you want.  Instead use a system that you can drill the concrete for anchors(after it has properly cured for a couple months), and epoxy those anchors into the concrete in the exact positions you want.  My first frame we wet set simpson straps and that did not work well.  After that we used knife plates anchored to the concrete with epoxied anchor bolts.
Check out this post.  I show the type of knife plates I have been using and what some others have done.
Knife plates
Whether you use a sill or not is up to your preference.  You do not have to use one though if you use knife plates.  One question is, how will you enclose or envelope the frame?  Will it be insulated or non insulated? If you decide to insulate, you may want to build a stud wall envelope.  It will have a 2x PT sill plate. 
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

Don P

Anchor bolts are readily available up to 14" long. From the formwork you can suspend/hold anchors or other steel in location. Wet setting of any anchor is usually frowned upon or worse by inspectors because it is easy to push the aggregate out of the way and have nothing but cream over the hook.

Malloy5944

Quote from: Brad_bb on November 21, 2019, 05:41:47 PM
One big lesson I've learned is to NOT wet set any anchors in concrete if I can help it.  No matter what you do, they never end up in exactly the position you want.  Instead use a system that you can drill the concrete for anchors(after it has properly cured for a couple months), and epoxy those anchors into the concrete in the exact positions you want.  My first frame we wet set simpson straps and that did not work well.  After that we used knife plates anchored to the concrete with epoxied anchor bolts.
Check out this post.  I show the type of knife plates I have been using and what some others have done.
Knife plates
Whether you use a sill or not is up to your preference.  You do not have to use one though if you use knife plates.  One question is, how will you enclose or envelope the frame?  Will it be insulated or non insulated? If you decide to insulate, you may want to build a stud wall envelope.  It will have a 2x PT sill plate.
I haven't decided to insulate or not but as of now I am leaning toward insulating. I haven't really even gone down the rabbit hole of how to enclose the frame. I'm not sure if i want to do cedar shingles or what. Honestly I would like the aesthetic of the Frame being exposed a bit on the outside but again I have no idea if that is practical or possible yet. 

flyingparks

Ah...this question. I too have battled this one. The last two frames I have build I wet set some oversized steel plates into the concrete. Then welded knife plates to these plates. Then attached the posts to these knife plates. So no sills. Not a fan of doing this. Very stressful. I prefer the idea of drilling anchor bolts in after the slab is poured leaving about 9 or 10 inches of bolt above concrete. Rip a 2x10 treated plate down to 8" and put your 8x8 timber sill on top of that. Bore a hole the width of the washer and counter sink your nut and washer in the the timber sill a bit. Should work just fine.

Hilltop366

I'll add some more questions.

Would a sill beam help spread out the load from the post verses no sill beam and a point load at the post directly on the slab?

Would it change the slab thickness / reinforcement requirements at the edge?

Don P


Stuart Caruk

Hands down.... Pour and cure a slab but include a turned down footing or a footing under where you will place your posts. After the slab is cured hammer drill for 7/8" rawl bolts. Laser cut (or use you tablesaw) lexan or acrylic sheet 1/2" thick, with the hole for the bolt. 

Screw on a Timberlinx connector to the rawl bolt. Drill 2 1 1/8" holes in your posts, slip in the wedge anchor and pull the posts solidly don to the concrete with the plastic plate (for a moisture break) in between.

Stuart Caruk
Wood-Mizer LX450 Diesel w/ debarker and home brewed extension, live log deck and outfeed rolls. Woodmizer twin blade edger, Barko 450 log loader, Clark 666 Grapple Skidder w/ 200' of mainline. Bobcats and forklifts.

Don P

In that book, go to about pg 170, the sketches of Miss Halls school storage barn. There is a 2x sill detail. That is another way although you will need something to provide uplift resistance.

For those following the scarfing discussion, notice the scarf in that sketch.

CJ

I, myself, am a new member to this forum joining last February to gain some insight into ideas and ways of going about building my 14'X18' cabin, as outlined in Will Beemer's book 'Learn to Timber Frame'. His was a 12'X16' design, but I just altered my dimensions to accommodate the larger foot print. I just found that the smaller design wouldn't work for my bunkie. 
That said, how I went about my particular build is I had a slab on grade poured @ 15'X19' with a (1) row of ICF blocks (@ 14'X18') to give me a crawl space under my floor, so if I wanted to add a water line or run some services, then I would be able to access them from the underside. 
I, too, went with 8"X8" sills that I placed on top of 2"X10" pressure treated wood and installed foam sill gasket  under them. As the cement was being poured, I inserted J-bolt anchors as used in most home builds. I countersunk holes in the 2"X10"s where the anchors would be as this would allow the nut to be recessed below the 8"X8" without interfering with it sitting flush. If that makes any sense? But before I snugged all of those nuts up, I placed 24" Simpson Strong-Ties under the pressure treated wood 4' apart, so when the 8X8" sills were in place, I would bend both sides of the tie up and secure them to the sill timbers with nails. Worked very well! That cabin isn't going anywhere Dorothy! One note though. You will have to notch out the 2X10" (9 1/2") to allownthe ties to align with the 8X8". 
I hope that this information helps you? I tried to explain it as simple as I could so that you could get the gist of it. If needed, I can attach photos? 
Oh yeah...one last thing. I went wider (6" extra all around the edge) on the slab than I did with the ICF blocks because I constructed a pressure treated knee wall on the outside that would support my exterior insulated walls. I used 2"X6" PTS for those knee walls. 

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