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Who did this to deck structure? Replacing deck beam

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  • Jul 31st, 2020 10:41 pm
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[OP]
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Dec 6, 2006
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Who did this to deck structure? Replacing deck beam

Just noticed this today. Did have someone trimming tree few days ago but I'm certain this wood shaving was not there...
IMG_20200712_201120.jpg

Looked up ahead is where my deck main cross-beam is. There is some rotting, but can't be from the rotting, way too much wood shaving. I do plan on replacing the whole cross-beam later this summer/fall if possible. Not something I can DIY myself, so want to wait til the covid situation dies down more first.
Got up on ladder to check the top side of the cross-beam (3 pieces 2x8 joined) just to make sure.... holy crap...

IMG_20200712_200552.jpg
IMG_20200712_200622.jpg
IMG_20200712_200821.jpg
IMG_20200712_200937.jpg

What did that? How to prevent that from happening again?
Now it's very urgent to get the cross-beam replaced ASAP..... that does not look safe at all....
Last edited by boyohboy on Jul 15th, 2020 8:56 pm, edited 1 time in total.
72 replies
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Mar 1, 2016
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Holy! A small beaver? My WAG is squirrel working through the rotten wood. I can’t imagine you’d have any problems once you replace, but I wouldn’t spend much time on that deck until you do! GL!
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Nov 18, 2005
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You probably want to replace the beam because having two 2x8's or 10's like that is not to code. Should be nailed together with a recess cut into the vertical posts
Screenshot_20200712-222146_Adobe Acrobat.jpg
Or maybe there were beams between the two 2x's and have rotted.

Read your post again and the middle one is completely disintergrated, holy cow never seen this before. Must of used untreated lumber for that
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Feb 11, 2007
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Wow, how old is the deck? Does seem like untreated wood. Maybe termites?
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Jan 25, 2007
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Drthorne wrote: You probably want to replace the beam because having two 2x8's or 10's like that is not to code. Should be nailed together with a recess cut into the vertical posts

Screenshot_20200712-222146_Adobe Acrobat.jpg

Or maybe there were beams between the two 2x's and have rotted.

Read your post again and the middle one is completely disintergrated, holy cow never seen this before. Must of used untreated lumber for that
Once upon a time you could put your beam either side of a post with a strong tie support and I think that is still the way you need to do it if you build a pergola same time. Its possible OP’s was done this way and they used non-treated wood to fill in the gaps as additional support near the posts, or along the whole thing.

Edit I built mine with beams on posts and the required strong ties for that style.
[OP]
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Drthorne wrote: You probably want to replace the beam because having two 2x8's or 10's like that is not to code. Should be nailed together with a recess cut into the vertical posts
Screenshot_20200712-222146_Adobe Acrobat.jpg
Or maybe there were beams between the two 2x's and have rotted.

Read your post again and the middle one is completely disintergrated, holy cow never seen this before. Must of used untreated lumber for that

Yeah lol, it is a *3*-stack 2x8 joint beam, with the middle 2x8's 1/2 to 2/3 of the width gone from the top for at least 2 feet length from what I could tell. Possibly worse, it's hard to see.
I'll def use strong tie between post and beams when I rebuild it.
engineered wrote: Wow, how old is the deck? Does seem like untreated wood. Maybe termites?

According to neighbor, the deck structure is likely 20-30 years old. Deck surface was replaced so only ~10 y/o.


No idea what did this. I'm sure the wood being somewhat rotted either triggered or worsen the situation. But it's definitely not the rotting itself, and not small insects. As you can see from first picture, there was big chunks of woods fell (thrown?) from the beam, and the wood shavings were mostly somewhat big too. The middle 2x8 did not get removed completely through, only the top 1/2 -2/3 of it. So looking at it from the ground (deck is on 2nd/main level) you can't see the problem... until I noticed the wood shavings on the ground today.

Squirrels, mouse, rats?
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Looks like squirrel damage to me.

I've come across some interesting damage over the years - squirrels, chipmunks, woodpeckers, mice, etc. - and this has the hallmarks of a squirrel that just started gnawing. The chunks are likely as big as they are because of how rotted the wood is.

Whatever did the damage, it did you a favour - that deck needs some structural work.
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May 29, 2006
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suprised it hasnt collapsed, not much meat holding that up. its strange how perfect the hole is, and you are certain this was a full 3x(2x8) beam? i have never seen anything like that before.
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boyohboy wrote: Squirrels, mouse, rats?
Most likely a rat. The beam was undoubtedly rotted and soft, and the rat dug in to make a little nest.

One small spot like that is not going to greatly impact the strength of the deck, but you should certainly investigate the extent of the problem in the other beams. I've seen some pretty careless deck construction that doesn't pass the test of time, and 20 years is more than enough time for issues to develop. At that time it was common to nail decks together instead of using hangers and screws. Nails split the wood, moisture enters the splits and starts rotting the wood (even PT is only surface treated), As the wood softens the nails start to pull out wherever there is pressure on the joint. Before you know it, the deck is collapsing.
[OP]
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Definitely right about the nails usage. The whole deck is all nails. Only the joist-ledger used metal hangers.
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Scote64 wrote: Most likely a rat. The beam was undoubtedly rotted and soft, and the rat dug in to make a little nest.
Interesting. Are you thinking wood rat? You have those out in BC but I don't believe their range includes Ontario.
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CaptSmethwick wrote: Interesting. Are you thinking wood rat? You have those out in BC but I don't believe their range includes Ontario.
Rats are very adaptable everywhere, and they can chew through wood easily. That damage looks too big for a mouse, too small for a raccoon, and not somewhere a squirrel would go.
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Scote64 wrote: Rats are very adaptable everywhere, and they can chew through wood easily. That damage looks too big for a mouse, too small for a raccoon, and not somewhere a squirrel would go.
Fair point. I've previously dealt with rats that made a mess of things in odd places but I am most familiar with rodent-caused wood damage as something they chew through to get somewhere, not to burrow a nest in the wood itself. It's why I asked about wood rats. Regardless, I would set out a rat trap.
[OP]
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CaptSmethwick wrote: Fair point. I've previously dealt with rats that made a mess of things in odd places but I am most familiar with rodent-caused wood damage as something they chew through to get somewhere, not to burrow a nest in the wood itself. It's why I asked about wood rats. Regardless, I would set out a rat trap.
Rat eh Expressionless Face... Does rat leave droppings behind?
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They do. Rat droppings are fairly large - like double the size of squirrel droppings.
[OP]
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For when I get to rebuilding the beam, is there anything good or recommended that I can lay on top on beam to prevent water going in between the 3 2x8? Looking at those butyl joist sheets but reviews are mixed.

Or pre-treat the wood with oil stain?
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boyohboy wrote: For when I get to rebuilding the beam, is there anything good or recommended that I can lay on top on beam to prevent water going in between the 3 2x8? Looking at those butyl joist sheets but reviews are mixed.

Or pre-treat the wood with oil stain?
I would recommend G tape for your beam. The crap you get at Home Depot / Lowe’s doesn’t adhere very well (Resisto Joist Guard). You could probably grab the right width at Deck masters or deck shoppe.
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boyohboy wrote: For when I get to rebuilding the beam, is there anything good or recommended that I can lay on top on beam to prevent water going in between the 3 2x8? Looking at those butyl joist sheets but reviews are mixed.

Or pre-treat the wood with oil stain?
Joist tape may not be wide enough to cover (3) 2x8's in width. It may also get expensive.

One option is to simply use roofing felt:
https://www.rona.ca/en/roofing-underlayment-0951003

You obviously have some work to do with cutting it but you will get whatever length / width you are looking for. I used this for all my joists / beams on my recent build and it only added an extra 20-30 minute to cut / staple. When tearing off my deck it is quite apparent why covering the joists is a good idea - you can see rot on the top of it but it doesn't go very far down. It seems with just some covering it would be significantly improved and greatly increase the life of your structure (obviously still have to change boards).
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Wouldn't metal flashing be ideal to cover the joists?
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TrevorK wrote: Joist tape may not be wide enough to cover (3) 2x8's in width. It may also get expensive.

One option is to simply use roofing felt:
https://www.rona.ca/en/roofing-underlayment-0951003

You obviously have some work to do with cutting it but you will get whatever length / width you are looking for. I used this for all my joists / beams on my recent build and it only added an extra 20-30 minute to cut / staple. When tearing off my deck it is quite apparent why covering the joists is a good idea - you can see rot on the top of it but it doesn't go very far down. It seems with just some covering it would be significantly improved and greatly increase the life of your structure (obviously still have to change boards).
I used Bluskin - turned out to be a more expensive option, but it worked. Comes in different widths. Pick something that self-seals since you're gonna be deck-screwing on top of it.

A friend used silicone caulk - not sure if that's worth it either.

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