Can anybody recommend a good way to anchor the butt end of logs to a concrete slab?
The logs will be posts for a 16′ x 16′ square gazebo. There will be 3 posts down 2 sides and the posts need to be basically what keeps the entire structure on the ground and also along with some 45 degree braces at the perimeter beam what needs to help keep the entire structure in rack.
I was considering epoxying a couple of threaded rods into the concrete at each log location and then drilling holes in the side of the logs and putting a washer and nut in through the hole like a traditional newel post anchoring technique.
Replies
how large are the logs...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
Has the slab been poured yet? If not, you can buy proper post anchors that are basically a piece of 1/4" flat stock with predrilled bolt holes. You do a plunge cut with a chainsaw and the anchor slides into the kerf.
If the slab is in place I suppose you could do something with Hilti bolts.
In my case most of the logs where sitting on top of sono tubes so I just made a "U" out of rebar, stuck it in the concrete, plunge cut, and bolted.
Be careful doing those plunge cuts.
Scott.
ps.... oops, sorry, should have addressed it to dogfish...
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Edited 8/7/2006 2:11 pm by Scott
You say that I can buy proper post anchors. Is it something specifically designed to be used with logs or is it Simpson post base y'all have adapted to work with your log work?
Be more specific please and let me know where I can get them.
proper post anchors -lot of options there
Own house has 7 ea 10" to 14 in dia posts 18 ft high sitting on 20" square risers above 30" by 50" footings. Anchors are DIY into plunge cuts as previous described. The DIY part of the anchors is to drill 3/4" holes (for 5/8" bolts, those holes are not easy to line up blind with a 600# log in the air) into 3/8" 3" wide bar stock 2 feet long, torch a slot into a 15 inch square piece of 1/8" plate for the log to sit on and protect from moisture, and weld the bar into the plate, then some cross rebar pieces below the plate and cast into place in concrete.
There were some pix in the local paper a few weeks back of B. Gates house, the posts were held with external steel up all 4 sides with what looked like hand forged brackets, probably pretty pricey.
Hey Dog,
No, it's not even close to something Simpson makes, but it is a simple bit of work.
I'm heading into town tomorrow, so I'll try to find one and snap a pic. If not I'll draw a diagram. I've always been pi**ed off at how much they cost. Around here (BC Canada) they're about $80 each. If you can weld and you've got some flat stock kicking around you could make them much cheaper.
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Edited 8/9/2006 11:51 pm by Scott
Sorry, didn't make it into town today; stuck at home on a rainy day with the kids. I'll snap a pic tomorrow.
Scott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
That's okay....
we still need to know what diameter the logs are..
that will have a lot to do with the size and style of fastener..Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!<!----><!---->
Forget the primal scream, just ROAR!!!
I will have to second the knife plate idea. whenever I've done log post they would spec out a 1/4 to 1/2" knife plate with two 5/8 bolts. Definetly predrill your holes in the logs. Washers will be needed on both ends of the bolts. Then plug the holes if you need to.
Good luck, Dave
See my reply to IMERC on this post.
Hi Again.
Here's some pics. They aren't exactly what I have seen in the past; I wasn't expecting rebar on the bottom half. Usually the flat stock extends downward into the concrete with holes or barbs punched into it for 'gription'. Either way, you'll get the idea.
As I said above, my inspector was happy with inverted 'U's of bent rebar. Way cheaper and easier. YMMV.
When drilling your bolt holes be sure to use self-feeding ship augers. Twist bits wander too much.
Good luck.
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Thanks so much for the pictures. So after you've set the log butt down over the bracket and you've installed and tightened the bolts(I assume 1 per slot) it should be pretty tight in the uplift direction but is it a little wiggly in the twisty direction? I figure this because your not exactly compressing the innards of the log against the bracket in a horizontal direction or do you tighten them till you get that kind of squeeze going on? Would it be worth putting some construction adhesive or epoxy in the kerf in the bottom of the log before slipping it over the bracket? Do you flush the top of the bottom plate up with top of the concrete or do you flush up the bottom of the plate? If you flush up the bottom of the plate to the top of the concrete what do you do with the resulting gap? I've seen where somebody went back and shaped a raised mortar bed around the base of the log to take up the gap.
I'm not a log specialist but this is for a good customer of mine(i.e. wealthy and easy going) and I tried to find a good log carpenter locally but the only good one I know is now in real estate and renovating a fixer upper. The other one is 6 months out and I need to have this project finished by Oct. 1st. I've done a little bit of log work(learned a little from somebody who was pretty good at it) before but not enough to consider myself experienced. I enjoy a good challenge so no bigger than this project is and considering that its an outdoor structure I think I can muddle my way through and end up with a nice finished product.
Thanks again for the pictures they are a huge help. I appreciate your efforts.
Edited 8/12/2006 9:12 am ET by dogfish
Hey Scott, your E-mail is no-workie..."If 'tis to be,'twil be done by me."
Hi Philter.
I don't know what you mean by 'email'. Does this forum have some sort of private mail function? Otherwise, I can be contacted at [email protected]. (Remove the one two and three.)
Scott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Yes the forum does....if you click on your( or others') name on the screen, you at some point posted your e-mail...you can send them an email... I'll resend, cheers,Phil."If 'tis to be,'twil be done by me."
Wierd man, I checked my profile and the box for Member to Member email is checked. I have no idea why it doesn't work. Did the message bounce or just disappear into the ether?
I sign into this forum with the exact email address that I posted above (minus the 123).
Oh well.
Scott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Hi Dogfish.
>>>but is it a little wiggly in the twisty direction?
My understanding is that the anchors are mainly for uplift protection. It is assumed that the post is loaded from above and also fastened to a structure from above. If you've got other forces to contend with please describe them and I'll ask around here for answers (I'm not an expert in this field, I just happen to live in an area where lots of people add post & beam log work to houses).
>>>do you tighten them till you get that kind of squeeze going on?
No, I don't think you could count on 'squishing' a log to dampen lateral stresses. It would eventually loosen up anway.
>>>Would it be worth putting some construction adhesive or epoxy in the kerf in the bottom of the log before slipping it over the bracket?
Wouldn't hurt, but I've never heard of it being done. BTW, I should have mentioned that our log guys put a layer of felt or tar paper between the log and the concrete. Just cut a large piece, fold it in half, cut a slit and slip it over the anchor.
>>>Do you flush the top of the bottom plate up with top of the concrete or do you flush up the bottom of the plate? If you flush up the bottom of the plate to the top of the concrete what do you do with the resulting gap?
So is this post to be buried in a wall? Seems to me that the central issue is what you plan to do with your finished floor surface. We don't have any log posts in our basement, so concrete/log interfaces weren't an issue. As for the posts on the main level, we set them up on 3/4" plywood shims so that the finished floor will slip nicely underneath once the shims are popped out. See the attached pics.
Cheers,
Scott.Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Hey Scott,
Again I appreciate all of your feedback on this post.
This will be a free standing shelter, 16' x 16' with a simple gable roof and I will probably put 45 degree knee braces at all of the corners. In other words it is in fact not attached to any other structure. The floor will be a simple concrete slab with a thickened slab at all 6 post locations(3 down 2 sides). The roof is meant to be cedar shingles over skip sheathing although I could sheath it with plyood sheets if it would help keep the structure in rack(sort of takes away from the rustic nature of this thing though). I think the knee braces will brace it pretty well but in order for that to be the case the posts need to be anchored at the bottom pretty solidly hence the reason for the adhesive/epoxy idea. Sometimes the wind here in the mountains can blow pretty hard and I don't want the owner to walk up the hill to his brand new tennis court(adjacent to the shelter which is there in case of rain and for the occasional picnic) to find a pile of firewood laying on th ground. I will probably use another posters idea and set the concrete to the bottom of the log anchors you suggested which will allow the post to be about a quarter of an inch above the concrete for drying purposes.
Oh, by the way this will be an all locust structure with the bark on. I will post some pictures if I have time to snap them.
Cool, sounds interesting. In my (non-expert) opinion I think the anchors plus epoxy should be fine. Your primary risk is uplift, but I think you're planning a very strong structure.
Here's an example of my el-cheapo log anchors. We've got 900sf of deck with 19 logs all fastened this way, and we *DO* get big wind here. For the upper story logs we just double-lagged them with 5/8" screws from below and heavy angle brackets from above.
View Image
View Image
Good luck,
Scott.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Edited 8/17/2006 3:11 pm by Scott
Edited 8/17/2006 3:12 pm by Scott
Nice looking house, nice looking site. What more could a gorilla ask for?
What I usually do is set the post on top of the steel hold down so that there is a 1/4 " gap on the bottom of the post so that any water that does get under there will be able to evaporate.
Also I use a asphalt shingle or piece of rolled roofing for the bottom instead of #15 paper.
Dave
I know that the way to anchor people butts, is to give them a computer and tell them about Breaktime...
They got some crazy little women there, and I'm a-gonna get me one.
~Fats Domino
I guess you could say that BT is a log written by anchored butts.
Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”
Edited 8/13/2006 1:49 pm by Scott
Here's the simpson version, works well, not cheap:
View Image
http://www.strongtie.com/products/connectors/CPS-PBV_APG.html
"Citius, Altius, Fortius"
After all the advice so far this seems like a simple solution. I can't imagine they cost much more than having my metal fabricator make the knife plate thing Scott suggested.
All great ideas guys!
They have worked great for me, they can be ordered as a kit, with the anchor and the epoxy in the kit.
It was a little more than a year ago that I used some, so don't remember cost.
To dress up the bottoms of the logs I used scrap copper from a countertop that I did, I cut 4" strips long enough to go around log bottom. I used copper roofing nails to secure, leaving a 1/4" space above the concrete for drainage. It looked great!"Citius, Altius, Fortius"