Concealed anchor for log column. Method? Product?
Natural logs,10 to 12 inch diameter at base, will bear on pier tops, three feet up from grade, and they need to be anchored.
What products and techniques are used to do this?
I was thinking of using a chainsaw to make a deep thin mortise, by stabbing straight in with the blade. If a big blade is used the mortise can be maybe 14″ deep.
If a custom steel anchor were made, its blade end, about 3″ width by 3/16″ thickness, can stick up from the pier top, and the mortised log end can go over it. Use an old bit to drill the log until you feel the steel, then use a new high-speed 9/16″ bit to get through the steel and then out through the other side. Counterbore in with a forstner, use 1/2″ bolts, plug holes.
Supply houses like Grainger have the bits one would need.
What else might work? I’ve surfed around for products, and am striking out.
Replies
Epoxy anchors?
How tall are these logs?
You could drill a hole in the end of the log, say about 7/8" diameter and as deep as you can find a bit (12" long spade bits are commonly available).
Goober the hole with some epoxy and drive a length of 3/4" rebar into the end of the log.
Drill a larger (1 1/2" or so) hole into the concrete pier as deep as necessary. Puddle some anchoring cement (Por Roc is a brand I have used), place the log with the dowel pin into the cement and brace it till it sets up.
Ideally, it would be nice to form the hole as you pour the piers, maybe use a length of pvc pipe as a sleeve.
Terry
There was an article about this in either FHB or JLC. I looked but couldn't find it.
I believe they did almost exactly what you proposed.
I've used the chain saw slot to blind mount stuff in the past and I think 1/4" steel fit well in the chain saw kerf.
Log Post Bases
You have pretty much got it. This is a typical detail in custom log home construction and is called a "Flitch Plate". Not sure how you are using this but it would typically be engineered by project arch. or structural engineer. This plate is usually embedded into concrete with rebar legs or better yet AB's to allow some vertical elevation control. Prep mortice in log with a plunge cut from a chain saw, Drill/counterbore log, Stand, plumb and brace, Drill through vertical flitch plate using steel bit. If you have trouble aligning all three holes pull log off base and oversize hole in steel plate. i also suggest using impel (Borate) rods to keep post bases from decaying. Good luck
Did pretty much as you describe 35 years ago on house we built and still live in.
Only went 10" deep, but used 2 cuts 6 " apart to gain some moment capability . (posts are about same size, 20 ft high -bsmt floor pads to 2nd floor)
Predrilled 2 each 2" by 1/4" thick steel with 7/16" dia holes near the top end , on 15" square 8" high pedastals from floor, . Steel welded to rebar in foundation
Plunge cut into log after measuring the in place dimensions. Soaked the log ends in penta for a day first (OK, cant get penta anymore, probably have to settle for a borate something now)
Had accurate measurements of the 7/16" holes relative to the footing. Filled the plunge cuts with tar, layer of roll roofing over the pedastal, dropped posts onto the steel stubs (using a 25 ft tripod) and let settle for a few hours - then measured from the pedastal and drilled thru with a 5/8" HS bit that I'd welded a 1/2" drill rod to.
Was able to hit all 14 7/16" pilot holes with the bit tip, installed bolt and tightned after verifying vertical on post.
BTW edit -- YOU DO learn more about bar kickback doing chainsaw plunge cuts in the ENDs of logs. Use the shortest bar you have and dont have your face in line with the bar <G>
Even today, after years of experience and over 157 stitches from various saw cuts over the years, I'd not try a plunge cut in a log end with my 30" bar, but a 12" bar should work well.