Outdoor arbor – near side is 2×6 ledger screwed into roof rafter tails, then doubled 2×6 beams supported by 6×6 posts on far side, with 2×6 joists and 2×2 trex spaced on top. Ledger to beam was three 3″ deck screws through ledger into end grain of beams. After a few years the beams started to sink downwards by 1/4″. I jacked them up and used 3/8 x 4″ lag screws. After a few more years the beams sank again by 1/4″ with the lags angling downward in the ledger. My proposed fix is to use 3/4″ maple dowels through the ledger and 4″ into the beams, grooved and ends chamfered for good glue bonding.
1. Will this work? 1, 2 0r 3 dowels per beam?
2. Should I put a 3/8″ lag in the center of the dowel for added shear strength?
3. Is there a better method given that I don’t want to use metal joist hangers because of appearance.
Thanks.
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Dehumidification is listed as a selling point for HPWHs, but are they actually effective at lowering humidity?
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
possibly the beam ends are rotting?
Could you post a picture or 2?
And the spans?
Thanks for reply. Beams are good, no rot. Span varies from 5-10'. You can see the lag screw head tilting downward with the weight. My theory is that by doubling the diameter from 3/8 to 3/4 and having a glue bond between the dowel and the ledger it will not tilt. I don't think shear strength is the issue. Your input appreciated.
Step back an take a few more. I understand the move you mention but am having a hard time seeing where all this wood is going?
2x2 Trex is heavy.
Thanks.
Front and back of the ledger/beam joint. 3/4" maple dowel would replace the lag screw.
Thanks.
I was hoping you show the whole structure.
Something is moving this.
Thanks
Looks like too much of a load for screws into end grain. Several dowels might be a bit stronger but maple is not a rot resistant wood and would decay fairly quickly. Some kind of a metal hangar is really the best solution without tearing the whole structure apart.
The temptation to half-fix this evident problem could make you very sad one day.
They sell joist hangers made to sit outside which have finishes easier on the eye than those meant to be protected and out of view.
If you keep drilling larger holes in the ends of those beams, there will be even less material to carry the load.
Consider yourself lucky this has not fallen on someone's head, but has given you the opportunity to correct this structural issue.
It sounds like you’re dealing with a classic issue of lag screws loosening in the ledger due to weight and downward force. While dowels could help, it may be worth considering a more reliable joint method, like using a steel plate or brackets hidden behind the ledger, if you're concerned about aesthetics. This would give more structural support without compromising the look. Dowels may not provide the long-term stability you're hoping for.