Fastening Log Ceiling Joists in Wall Log Pockets?

[kantuckid]

I would appreciate some wisdom before I fasten my log ceiling joists in their pockets. I'll drop the joists in a day or so, thus time for discussion.

The joists ends are 6" thick x 6" wide and will sit down inside & flush in a wall log pocket extending 4" deep and resting upon the wall log below the pocket.
 
I'm considering either: 
#1-  single 9" SPAX (self-drilling thus no splits) wall log screw in each (same as the walls get when stacked)
 #2- two 6", "toe screws" in each end (also 5/16" SPAX self-drilling)
#3- one vertical 3/4" oak peg. 

The joist pocket log is already screwed down in its place, so well retained already. There are several more wall log layers above that to extend the lofts headspace.

There are 5 joists overall holding the loft floor 2x6 decking floor. FWIW, span is ~ 14' 6" overall.  
Your thoughts? Thanks!

[Jim_Rogers]

Depending on the spacing distances I would believe that the 3/4" peg is not going to be the best choice. There could be not enough wood between the peg hole and the end of the joist to prevent blow out should there be any horizontal stress on the joist.
I would go with one of the screw ideas with at least 3" of threads penetration into the logs.

Hopefully DonP will have some advice for you.

Jim Rogers

[Don P]

Jim and I were posting on top of each other... I do not disagree with his observation, it depends on load and direction.

Is there any shear on these or are they just keeping the joists in place? If the latter then any of those is fine. 

Put the engineer son on the joist size, that sounds at least 2" shallow to me.

[kantuckid]

The fastening is to keep them in place, which would happen anyway was the logs go on down top of them. I cannot see much shear effect but do agree the oak pegs too close to the end grain of the joist to do much.

I watched one of the Youtube videos from "The Bearded Carpenter" who used one, old style, huge lag bolt to pin his joists. I though his choice had the same limitations Jim mentions.

My joists average around 7.5" to 8.5" in depth with the ends pared to 6x6's. The pocket depth is same as wall log height. The spacing is 4 joists 24" on center, last one at outside edge is 20". I allowed for a slight over-hang and the stair stringers get to butt up on the last joist.
 The 2x6 decking tucks into a 2" pocket in the end wall log.  The OAL of each joist is 15' 1/4" with the span actual at 14' 6 3/4". 

My civil engineer son and his bunch is off kayaking in N GA mtns.  

Span charts show a 6x12 for 14' but this is what I've got to go with. I had originally cut some round poles 8" diameter and after a couple years of exposure & materials issues, decided to ditch them.

My home is a 16' span with 8" diameter round logs holding a somewhat similar sleeping loft BR.  

[Don P]

I thought I heard banjo music  :D.

Round logs carry higher strength values than sawn beams. What you are doing is called a SRTB, a sawn round timber beam. you may remove up to 3/10 of the diameter on the TOP to create a flat surface for flooring. In other words you can only saw thru fiber on the compression side to retain those unsawn fiber numbers.
Calc is here;
Log Beam Calculator (forestryforum.com)
I used (30 psf live load + 10 psf dead load) x (14.5' x 2') =1160 lb load. Looks good at 8" midspan diameter.

I'd use ~8" fastenmaster screw or similar, full thread penetration into the bearing log. If you have log hogs they are a little heavier. We used to use a 3/8 x 10" lag in a predrilled hole for that before the structural screws came around.


for the wood geek crowd, compare the Fb strength in a round timber to the design strength in the heavy timber calc. Keep that in mind if you need to go heavy and long, leave it round if you can. In this example I was using #2 EWP in round Fb is 1450 psi, in heavy timber it is 575 psi. Sawing is an affront to a tree but it does make them easier to use.

[kantuckid]

You have "Deliverance" on yer mind...  :D Burt was good in that one. My wife and I have canoed all over the USA, still have the one alu with the scars. She got to where she asked if this next river was more angry than the last one. Best time was in TN, just below KY we'd took off from a low water bridge in front of a country store and after about a couple hundred yards the entire stream ran under a rock overhang and we dove for the floor and roade it out of the headbanger. It fed into the KY Barren River which is fairly tame. 

Our twin sons did their river, over and over so all got to make the rides. My grandson, age 3 told his daddy "kayaking is fun, lets do it again!" . He's been on his older sisters bicycle and asked his dad to remove " these things", meaning her training wheels. He knows no boundaries. 
3 of my granddaughters descend on us Wednesday, and I will experience a work stoppage here while we mess around outdoors.
 
You guys have prompted me to re-visit my peeled pine poles I cut for this very role! I may spend the cold a.m. today sanding them on my forks. Last I looked they had some small oyster shell on the dry cracks but no rot. 
I really like these SPAX  T50, flat washer head log screws. 6" smooth, 3" of threads. They are a sub for a 5/16" lag but drill their way in and never a split.
For the record, I don't miss the 12x3/8 spikes I used on my house. Still use the same 6# sledge to persuade wood though it's a tad heavier in my senior arms. 

[TW]

In my part of the world the normal way of doing it is to cut a dovetail. No pegs not bolts needed.

[kantuckid]

Being less of a purist, I'm slamming mine down with a 9" long SPAX screw.  The first one I set was so tight, I was up and down two ladders sledging it in.
Or maybe I'm somewhat lazy?  :D 
In my mind, either way is an adequate wall tie. These T-star washer head screws apply immense forces that far exceed older style fasteners.  I think I read nearly a ton of downward force from my 5/16 x 9" version.