Repair rotted beam

[zakthor]

I have an ornamental thing over my garage door. Its made from 2x12 douglas fir with 21’ span. Each end rests on cross pieces bolted to a pair of 8x8 posts.

I occasionally put plywood on it to clean or work on the windows above the garage.

Yesterday i stepped on a beam end and my foot crunched through from rot. Rot under the paint. Rot extends 10” from end of beam, that beam end is in a soggy poorly vented area. Rot was concealed by a thick layer of paint so i hacked at it and found the two beam ends are lot of mush.

Anyway. Rather than replace all the wood id like to replace the rotted sections with a scab and support them with sisters.

I took out the closest cross brace and have got 24” of overlap for the sisters before the next cross brace which has no rot.

This isnt a public bridge - it really isnt even structural, but how should the sister be attached? I see a lot of different recommendations but they are for real load bearing like roofs, floors and parking garages. I dont mind doing it right.

Thinking 1/4” steel filch plate and 1/2” bolts in w pattern? How many bolts? 3 per foot? Is 2’ overlap enough? Can anyone point me to authoritative instructions for how this sistering should be done?

Also, id like to cap the beams. I see places selling little beam end covers but why couldnt i fab some full length beam covers out of sheet? My google foo is weak what is that sort of sheet fabbing called?

[masraum]

Interesting. I can't help, but I'm super curious to see the result of the thread.

[flatbutt]

Subscribed

[zakthor]

I think this is the best how to that ive found.

https://dcstructural.com/pdfs/technical/200706_from_experience_flitch_plate_beams.pdf

Seems like it wouldnt be bad to drop a pair of 1/4” plates between the sisters, but also unnecessary given the rest of the structure. Maybe iits a waste to pay the $150 to buy that metal.

this trellis thing isnt built with hangers. Blocking cross pieces are just casually banged together with pairs of 16d nails. Its designed to hold itself and some jasmine vines, and me abd my plywood when im washing the windows.

[HardDrive]

Doesn’t look like you have much material left. There is a penetrating epoxy product called Rot Fix that works well on rot. You drill some holes, and the wood soaks this stuff up. It’s amazing. I used it on a rotted sill plate in an are that would have been painful to fix.

[look 171]

I am a huge fan of epoxy but this maybe to big for epoxy. How about a pic from further away. I like to see more rather then the close up of rotten timber. Should be an easy fix. Who knows maybe epoxy is the key here. I use Abratron. Used their structural epoxy on my parents home way back, 20 years ago, its still there with no issues.

[gduke2010]

Just replace the beams.

[herr_oberst]

Originally Posted by gduke2010

Just replace the beams.

The best answer. Unfortunately wood is frickin' expensive right now. So is paint.

[URY914]

1/4" plate to too heavy IMHO. It will be very hard to handle above your head.

[gregpark]

I would replace the beams. Like a car showing a bit of rust, it's all suspect at this point. Even more difficult to locate rot with the wood having been painted. You could probe with a screwdriver but more dry rot could develop later. This beams do not look healthy at all and 2x12s at 21' long are pretty heavy without even bearing additional weight

[zakthor]

Ok i dug around some more with a hammer. The beams are good everywhere but at this end.

But the horizontal supports at this end are rotted too so replacing more garbage wood.

You all are right i should just replace the beams, theyre $45 each but scarce right now, so far a few weeks to get. Replacing means an entire rebuild which at my slow rate it with delays would be a month before complete.

I ordered the metal, its $75 for two long plates. Also ordered $20 of simpson stuff and their screws. Ill be done on tuesday.

I found that there are people with ‘van brakes’ that form sheet in your driveway. I gotta find one of these guys to fab cute little caps for these joists. Especially the sisters.

I promise the next time these beams bat an eye at me im nuking them.

[zakthor]

1) The Wood:

First thing, the wood is cedar not fir like I said above. Explains why it lasted 60 years. Oh and its rough sawn so normal faced wood won't match.

Things did not go as planned. I went to get the $45 beam sections and they were just trash. Totally unusable warped and checked, like for a crate. yeah I'm glad I didn't pay ahead and have the wood delivered.

I started calling around and cedar 2x12 has gotten real 'spensive. Some local places can get it in a week and want $35/foot for 10' and under, one place wanted $55/ft for 12', but no one even has rough sawn. I found a place 45 minutes away that had s2s 12' 2x12 that were 'ok' for $7.50/foot so I went and they were good enough so I bought them. That gives me enough to replace half the inner beam and replace the rotted joists. The outer beam is basically the most visible thing on the front of the house. I just don't want big bolts on it so just need to find a 20' rough sawn 2x12, that is decent, and won't break the bank.

Called and called. Called craigslist used lumber seller and he recommended a place 90 minutes north. They called their mill and explained what I wanted. They have material to make me one, not two, for $320 so $16/foot.

So it goes. Guy said he was shocked how bad cedar is these days. They sell stuff today that 30 years ago they'd have used for firewood. I'm going to head up next week so I can go see the wood before they make the beam out of an existing 4x12. They say it is 'grade c'.

Anyway. I'm sure glad I saved the good cedar when I replaced my deck 15 years ago. That stuff is all clear and rift sawn 12-16' true 2x4. Unfortunately one side coated with a very strong coating...

2) The Surface

Like an idiot I got the stained house painted 20 years ago. I used some awful 'superpaint' that seemed to lock in moisture. That and neglect is what ruined the cedar. So this whole apparatus out front is painted cedar. We have a paint color we like but... I just can't bring myself to paint this stuff. Isn't that a geneva convention crime?

I've been sanding and staining some fir beams in the san juans using a high voc cabots deck and siding in 3000 natural. Its held up really well to the salt spray and winter winds. They have a new product called 'Australian timber oil' that looks a bit darker so I bought a can to try.

Today I cut the rotted half of the inner beam free and built a replacement with a joint with one of the $120 12' 2x12:



The piece in the pic is assembled backwards those chips around the hole will go against the metal plate.

And here you can see the oil finish. Its not dry in the picture but wow did it darken the knots. The stuff is really thin and soaks in deep.



I am going to see how it looks when the inner beam is installed, then maybe use this stuff on that $320 front beam too. If it is just too weird to have a natural wood color in front of all that paint then I could stain it dark later. Or I could just sand all the paint off everything else so its all matchy match.

3) The 2x Edge Caps

I asked above about getting sheet caps for the 2x to keep the rain off. Called probably 10 places and all but one estimated $8-$10 per foot for 4" wide sheet cap. Union labor? I mean I value skill but that seems nuts, I've seen people who are good with a brake and 100' might take 20 minutes and the material is cheap. So I guess I can rent a brake and make them myself? I need about 100 feet... the last place I called for an estimate we discuss and he's like: send us the dimensions and we can have it by... wednesday? Uh... you can't give me a quote until wednesday? No... we'll have it done by then. But how much? Oh... uh... about $100? Yeah so thats the place. Precision Sheet Fabrication on aurora in north seattle. Highly highly recommended by a friend, so probably not a scam.

I need to get the thing built before I can make the dimensions. I think the caps with little rain drip edges will go a long way toward preserving the wood.

[zakthor]

Fitted beam this morning. Ok that raw color wont work. Oh well. It is pretty but no. Ill let it harden a few weeks then zap with the dark stain.

I put two coats on 15 minutes apart and board was dry enough to handle this morning.

[Alan A]

I’m guessing you don’t want to do a scarf joint?

[zakthor]

Originally Posted by Alan A

I’m guessing you don’t want to do a scarf joint?

i made a 3d scarf to join my deck railing. But here its 12 feet into a 20’ span. Id need more wood to make a scarf and for strength wouldnt i need to have plates on both sides?

I did the calcs and what i made is stronger and stiffer than the cedar. The cedar is quite weak. Not good for house parties but will be adequate for me to wash windows.

Everyone thats visited loves how the oiled cedar looks and thinks i should leave the the new stuff alone. It looks like furniture. Too bad i couldnt source tight clear old growth.

The timber oil dried hard and sandable after 2 days. Is great to do it on these hot dry weeks. When it doesnt last i can pressure wash and dark stain, maybe next summer.

[zakthor]

Ok, lots of progress complete just in time for the rain. Still a little caulk and paint needed on the windows but the rot is all gone.

I received the new front beam, it is way nicer than I expected.

Replaced everything rotted, its all cedar coated with the cabots timber oil. I'll let it all weather over the winter, then we'll see about applying the dark solid stain...

Replacing all the wood would have been $2000-$2500, so by repurposing solid sections I saved $1000-1500. If that joint bothers me I can replace the center beam in the future.

I'm still ok not tearing it all down and rebuilding from scratch, still just seems too wasteful to toss all that wood.

I used strongtie screws for the first time, quick and removable, and the thing is a lot stronger than it was before. I never looked close but those 'girders' that support the beams were held to the side of the post with pairs of 1/4" lag screws. I replaced with 1/2".



Now I'm on the hook to measure and order flashing caps but gosh do I really want a vacation.

Called cabots this morning, they say their solid water based stain will stick to the timber oil if I let it weather all winter and then give it a light sanding.

Whew.

[911 Rod]

Why not just use pressure treated wood?

[zakthor]

Originally Posted by 911 Rod

Why not just use pressure treated wood?

That would have been ideal. Ive seen pictures of pressure treated southern pine that look fantastic but in person its been garbage. I asked around and the only stuff I found has ugly surface processing. Is there a better 'appearance grade' pressure treated?

[rfuerst911sc]

Why not use an oil based stain for top coat ? It should protect the wood better than latex .

[911 Rod]

Originally Posted by zakthor

That would have been ideal. Ive seen pictures of pressure treated southern pine that look fantastic but in person its been garbage. I asked around and the only stuff I found has ugly surface processing. Is there a better 'appearance grade' pressure treated?

Maybe it depends on where you are?
The PT here is a very pleasing colour since they dropped the green years ago.
No one stains or paints it other than for looks. (I'm not an expert though)