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Wood Guys - This a Problem?
4

Wood Guys - This a Problem?

Wood Guys - This a Problem?

(OP)
***I'm wholly unaffiliated with this project***

Driving home over the weekend and saw these condos under construction. Thought the framing was interesting so I stopped for a look.

Any concern with the checks/splits in those cantilevered 4x8s? Or is this already considered in the lumber grading?




RE: Wood Guys - This a Problem?

That's actually a pretty cool detail. I know what you mean about the checking though. It feels as though that would totally compromise your horizontal shear capacity and render the thing two independent pieces of lumber. However:

1) Pretty much every beam and column in every ski lodge in all of Canada has this.

2) Some massive glulam columns at the university of British Columbia have this.

3) When I've looked into it myself in the past, the answer seamed to be that if it was truly partial thickness checking rather than actual shear failure, it was okay. Sadly, I failed to file my hard won research and am unable to produce it here.

4) Part of me feels as though this is just something that woodies choose to turn a blind eye to because their woodies.

RE: Wood Guys - This a Problem?

Those are two 4 x 4's stacked. Run the numbers. They might be spiked together, ?? The wood is not pine, probably red wood. Strong stuff.

RE: Wood Guys - This a Problem?

Splitting or just water mark?

RE: Wood Guys - This a Problem?

Looks like a future Balcony collapse thread in 8 years time to me. ...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Wood Guys - This a Problem?

And you commenters are engineers??

RE: Wood Guys - This a Problem?

Since the Berkley collapse I hate the idea of timber balconies. You can’t rely on the weathering detail to prevent decay.

What’s up with the ground floor lateral stability here?

RE: Wood Guys - This a Problem?

Hmmm, I don't like it. It's not just that the checking exists. But, that it exists at this stage of construction. I've seen checks like that in wood that's been exposed and drying out for 20 years. But, at this age?! If I were the engineer on the job, this would make me want to (at the very least) switch to an engineered wood product for similarly sized beams in the future.

I'm not saying it's inherently dangerous. Things like this can be optical illusions, after all. And, the wood had to be rated in that condition. Presumably, that means it would still satisfy stress requirements.

Lastly, I actually kind of like the long back-span detail for the cantilever. That bodes well for the future safety of the balcony. Someone else mentioned decay. But, we don't know what architectural detail there will be to prevent that. I don't do enough of these types of decks to say that they shouldn't be done out of wood. Especially if they're a one-off family home. For condos and apartments with a balcony like this repeated 100 times, it might be worth it to use some other material. But, tough to justify another material for a single family home.

RE: Wood Guys - This a Problem?

Quote (MIStructE)

What’s up with the ground floor lateral stability here?

That's almost always the way of it with these row house looking things over here. One hopes for an interior shear wall hidden away in there. There was a fun LinkedIn video a while back where somebody tapped the side of one of these with a backhoe and it pancake racked just like you'd be afraid it would. Of course, that changes nothing.

RE: Wood Guys - This a Problem?

I actually saw that LinkedIn video! Yeah, hopefully there’s a shear wall behind there somewhere.

RE: Wood Guys - This a Problem?

I feel like:

1) The guard rails on the sides of the balcony will be sturdier than usual but;

2) Not so much with the guard rails on the front of the balcony unless the rail's meant to span to the sides maybe.

RE: Wood Guys - This a Problem?

(OP)
Here's a shot of the finished condition.

RE: Wood Guys - This a Problem?

Well that covers up all or any evidence of rotting wood alright.

The fact that there are only two beams is what causes me the issue and the fact non one will know they are a bit dodgy until the balcony gets rather "spongy" or just plain collapses one day when a bunch of people lean on the rail admiring the view.

Putting the drain right by the joist could be very bad if the detailing and sealing of the drain isn't perfect.

Remind me never to sit on a a balcony where you can't see the beams or attachments to the building....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Wood Guys - This a Problem?

That stucco facade has no weep capability at the bottom of the balcony. It will cause the wood to rot behind the stucco...unseen until too late. Makes me suspect the other waterproofing details as well. If this were in Florida, it might be one of my projects in 4 or 5 years!sad

RE: Wood Guys - This a Problem?

I'm curious:
> what holds the joists onto the beams? are they just toe-nailed in place?
> is the gap between the bottom of the joist and the left side beam supposed to be there?
> is the slope of the deck typical?

TTFN (ta ta for now)
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RE: Wood Guys - This a Problem?

OK guys. That's two 4 x 4's one above the other. If you go to a typical lumber yard ask for a 4 x 8 and you likely won't find any. However, ask for a 4 x 4 and they have plenty. May explain the situation. Was there a design for a 4 x 8 or two 4 x 4's? Likely a 4 x 8. Or no design?

RE: Wood Guys - This a Problem?

@oldestguy, based on the pictures I'm looking at it's definitely not two 4x4's stacked on top of each other.
The following two pictures show splits/checks that are obviously not straight, which would be required for two 4x4's





The end of this beam isn't split at all, indicating it is one piece:


Go to a typical lumber yard and tell them you need lumber to build a condo and they will order it all for you from their suppliers, it won't come from their stock.

RE: Wood Guys - This a Problem?

I really can't tell if they are two 4x4's or single 4x8's. (I've really zoomed in on all the photos too)

Some of the photos showing the end grains makes me think they are single 4x8's, but then the side elevations make me think that maybe it's two 4x4's with beat up edges.

I think AzCAT needs to go back into to the field and get us better photos. glasses

RE: Wood Guys - This a Problem?

Joists onto the beams looks like gravity to me...
Gap is supposed to be there as it seems the two beams are at different heights. Interestingly it shows on the RH beam that the cantilever is about 1/3: 2/3 You assume the LH beam des the same thing
Slope looks a little steep but pooling water is a big issue on decks so maybe they go for a 1: 20 or something

The other thing about stucco is to the uninitiated it makes it look like the frame is brick or concrete not timber, ditto the important bits holding the balcony up.

I'm sure one of the balcony collapses recently looked like that.

this one I think https://www.eng-tips.com/viewthread.cfm?qid=389494



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Wood Guys - This a Problem?

Just curious, is rot much of an issue in Arizona like it is in other climates?

RE: Wood Guys - This a Problem?

Of course it's a 4x8 and not two 4x4's. I thought oldestguy was just being a smart ass. You guys either need to view this on a PC rather than your phones or hit the optometrist.

RE: Wood Guys - This a Problem?

Quote (Ron)

That stucco facade has no weep capability at the bottom of the balcony.

The balconies pitch heavily to one side. It may just be that we're seeing the other side in the photo with the stucco.

RE: Wood Guys - This a Problem?

Or the drainage is getting routed here.

RE: Wood Guys - This a Problem?

Little Inch -

Thanks for the link to that previous thread.... For those of us who don't deal with this issue often, it's helpful to have links like that in this thread. :)

RE: Wood Guys - This a Problem?

How's come every shot on the sides shows that line between two 4 x 4's, in the exact middle, full length. Not a natural split on every one. No joke. Makes the job look even more questionable.

RE: Wood Guys - This a Problem?

(OP)
Here are some zoomed shots from my original photos.


RE: Wood Guys - This a Problem?



RE: Wood Guys - This a Problem?

Not much doubt about azcat's shot.

BA

RE: Wood Guys - This a Problem?

Based on what we've seen so far, I feel that this looks like an uncommonly well detailed and constructed building of this sort. Ever since that damn SF balcony incident, we all seem to get frothy at the mouth every time that we see any balcony that's not an extension of a concrete slab.

I've been involved in a few wood/cfm projects where precast balconies were substituted for durability and that institutional feel. Anybody who's had a look a the fragile connections back to the stud walls in those setups is likely to feel safer on cantilevered wood, even with the rot potential.

RE: Wood Guys - This a Problem?

The member should have been rejected, rather than incorporating it in the structure. A better choice would have been a galvanized steel beam.

RE: Wood Guys - This a Problem?

The split beam is inviting troubles down the road. The stress flow of 2 - 4x4 wouldn't be exactly like 1 - 4x8, which was the base in design.

RE: Wood Guys - This a Problem?

Don't shoot the messenger. Obviously, a full width, mid depth crack over a prolonged length has to have implications for horizontal shear transfer. It's pretty rare for that actually to be the case however.

RE: Wood Guys - This a Problem?

Wow! Glad that I am not a wood guy.

RE: Wood Guys - This a Problem?

Meh, every material's got its issues.

Steel / CFM: buckling, buckling everywhere.

Concrete / Masonry: can't really ever figure out your loads or deflections with any certainty & minor detailing errors are catastrophic.

Wood: Tension perpendicular to grain and checking.

I'm holding my breath for structures built from monolithically site cast, 36 ksi steel rectangular sections.

RE: Wood Guys - This a Problem?

Yeah checks are common in wood. I wouldn’t pretend to know the acceptable limits.

Not sure anyone in this forum does from the sounds of it!

RE: Wood Guys - This a Problem?

This document is a little older but searching checks gives some good breakdowns on the impact. American Wood Council (PDF)

Repeated row houses like this are typically done as cheap as possible in some instances that means if its a big developer like Pulte, etc. pay a little up front premium to get some performance based design to side step some code criteria and satisfy the AHJ (Authority Having Jurisdiction) if it will net them material and labor savings. Part of the penny pinching is also the grade of lumber I wouldn't be surprised if they were using stud or standard grade lumber which would explain the checks and some of what looks like twist also.



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https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:
https://github.com/open-struct-engineer

RE: Wood Guys - This a Problem?

Which one below is better description of the defect in the OP's photo?

RE: Wood Guys - This a Problem?

I don't even see a check in the picture on the left that you posted, r13.

But, based on this picture below the wood is checked, not split, as the crack does not go all the way through the timber, it terminates at the center of the timber (probably the center of the tree) and does not go all the way through.


Here is a decent blog post on the subject of splits/checks http://www.woodscienceconsulting.com/wood-science-...

RE: Wood Guys - This a Problem?

The photo was taken from the referenced material, it gets me too, so posted for comment. The definition below each seems good though. The earlier reference material referred to several ASTM documents, which may contain grading guidelines and acceptance criteria.

RE: Wood Guys - This a Problem?

1) I believe that these would be the National Lumber Grader's Association specifications for this.

2) No limit at all for #2 or lesser.

3) In my opinion a more reasonable limit for #1 and better.

4) One would think that "ends" would really be the high shear location at the start of the back span for a cantilever.



RE: Wood Guys - This a Problem?

After checking on all referenced material, I find the contractor is quite experienced and smart in leaving the face with checks facing out, and leave the smooth (assumed) face inward to support the interior joists, and not violating the rule - not to glue or use strap to close the checks, for which may impede the wood from expand/shrink during the next drying cycles.

From KtooK's latest excerpt, can this 4x8 graded as No.1 lumber, with the checks near/at ends less than 1/4 of the thickness? Seems the check outside of the end region does not count towards grading.

RE: Wood Guys - This a Problem?

OK Ya proved it. This OG gives up. One piece.

RE: Wood Guys - This a Problem?

The drainage on the top of the balcony doesn't matter. It looks like a t-bar drainage system on the balcony, but unless that's flashed incorrectly that doesn't matter either. The problem is that stucco is not waterproof and neither is the paint....water will get in there and without proper weeps it won't get out....thus the rot.

RE: Wood Guys - This a Problem?

Of course the drainage on top of the balcony matters. It's a bucket of water otherwise. But, if what you're referencing is a lack of weep screed at the soffits then, sure, I take your point.

RE: Wood Guys - This a Problem?

If it is a t-bar perimeter system on the balcony (which is common), the drainage is under the slab, not on top. Yes, you want most of it to run off, thus the conductor head, but there has to be waterproofing under the slab.

Yes, that's the type of weep to which I was referring.

RE: Wood Guys - This a Problem?

I certainly close my eyes and trust the system. The Australian code simply limits the opening width (3mm) and length of the check (L/4 to L/2), but not the depth of the check. The depth just needs to be less than all the way through the stick. Got 1mm hanging on at one edge? That's a check, not a split. Check is fine for half the length; split of any length would be rejected. Internal checks are limited to 10% of the cross-section though. ponder

Moving to USA because you have more documents explaining code provisions, TFEC Tech Bulletin 2018-10 says "the tabulated allowable shear stresses [in the NDS] are based on the conservative assumption of the most severe checks, shake or splits possible, as if the timber were split through its full thickness for its full length." It also says there are limits on the depth of check for the higher grades which is more encouraging than the Aust requirements.

What I don't get is the reasoning behind only reducing the allowable shear stress because of the hypothetical full-length full-width check. That could halve the bending strength if located at mid-depth, whereas I picture two parabolic shear stress distributions that sum to the same as the single full-depth distribution. More than happy to be set straight here.


RE: Wood Guys - This a Problem?

I suspect that the TFEC verbiage was not crafted with sufficient precision. A check that goes full width becomes a split and there are limits on splits which seem geared toward the preservation of horizontal shear capacity where you'd want it for composite behavior. So it's spurious to imply that there's such a thing as a full width check.

RE: Wood Guys - This a Problem?

Quote:

That (full length, full depth checks) could halve the bending strength if located at mid-depth,...

Why's that?

RE: Wood Guys - This a Problem?

Because you'd be effectively assuming no horizontal shear connection between the upper and lower parts of the beam. No VQ/It shar flow stresses.

RE: Wood Guys - This a Problem?

Quote:

What I don't get is the reasoning behind only reducing the allowable shear stress because of the hypothetical full-length full-width check.

They reduced the allowable shear stress, means there is some shear stress passing through the checks (not completely lost). By limiting the shear stress, the span length and intensity of loading will be reduced as well, which in turn reduces its effects - moment and normal stresses.

I shall have highlight the word "halve". Thinking 2 4x4 stack together, what is the moment capacity - with limit set on loading, and without?

RE: Wood Guys - This a Problem?

If you don't have shear flow, you essentially have a pair of 4x4s. Since moment capacity of a rectangular section is proportional to the square of its depth, a 4x4 would have 1/4 the bending capacity of a 4x8. Stack two 4x4s without a connection for shear flow, and the resulting stack has half the moment capacity of a single, solid 4x8. So long as the check is a true check as KootK describes (doesn't pass through the entire width of the member), there's a shear flow connection that allows the whole section to act together.

RE: Wood Guys - This a Problem?

My fault, as I didn't make my point clear.

A 4x8 is rated to carry the shear due to 100 plf uniform load. Due to the presence of the seam (in mid height), the allowable shear is reduced to effect a 50 plf uniform load (by code). Does the code needs to further stating limit on the bending strength of the 4x8? No. My point is through "reduction" in shear capacity, the code has already reduced the moment capacity without the need to limit the consequent flexural stresses.

RE: Wood Guys - This a Problem?

I'd agree with that. As long as your horizontal shear capacity at the check meets your horizontal shear demand, you've got the bending capacity that you were expecting in the normal way. I think that steveh39's thing was that, if you have NO shear capacity at mid-height because you've got full width air space there, then surely your bending capacity must be that of two independent pieces rather than that of a single composite piece.

RE: Wood Guys - This a Problem?

This thread shall be carefully reviewed - Stacked Beams, Link

RE: Wood Guys - This a Problem?

r13,

In your last sketch (boards bonded together), the end slope should not be vertical.

BA

RE: Wood Guys - This a Problem?

Picky eye:) Agreed.

RE: Wood Guys - This a Problem?

I think that this is a really bad construction detail/method. I won't go as far as saying that this is downright dangerous but it looks pretty bad. I've seen engineering drawings for wood frame buildings like this (especially multi-res) and the detail can be pretty lacking at times. It's usually just a slathering of joist/beam sizes, post locations, etc... along with a bunch of typical details. Some of the more complex framing gets overlooked at the builder has to 'wing it'. Scary stuff sometimes. Also worth noting is the fact that this building is using a floor truss system (instead of engineered joists or cut lumber). This can sometimes lead to a disconnect between the main structural consultant and the truss supplier. Quite honestly, the truss suppliers would be well-off paying their own engineers good money and just do up the whole structural system for the wood framing instead of the owners paying two separate firms to work against each other.

Framing residential housing with a wood truss system gets complicated quickly. The rim board (or rim truss or whatever they would call it in this case) highlights the extra complexity. The balcony framing still looks a little convoluted none the less. If the ceiling is the same height as U/S of balcony they could have simply cantilevered the floor framing out at least until the exterior wall over. The house on the left has the floor system cantilevering out but I think it has a different balcony. If the slope (for drainage) ends up being lower than the inside floor height they can still make a truss that accommodates for that without much additional cost (it's shop fab'd anyways). Maybe I'd understand their approach better if I saw the drawings; perhaps they didn't want a beam getting 'squished' by that corner post but there's not much load there anyways. If it were my house I would have really preferred to see a 3rd cantilever for some much needed redundancy. I don't quite get why the truss attachment at the bottom-right looks so flush/square and the bottom left looks so out of wack - it looks like somethings off there. They would have had to do something their prior to closing and installing the exterior finish (stucco?). The trusses look like there is no positive connection to the cantilever beams (maybe I missed something but hopefully it's not toe nails). Quite honestly I think they could have framed the balcony without trusses but I'd have to see the bigger picture. The cantilevers need a strap or some sort of hold down at the interior. Maybe it exists but is hidden by their temporary guard rail. Hopefully this is a very favorable climate. It would have been much wiser to go with an engineered product, or at least a pressure treated product (I forget how much weaker PT'ing makes wood though). A lot of the issues we're seeing on the wood could be due to weathering. Maybe it was really wet followed by a dry period.

My best guess is that the engineer came to site, saw this, and made them fix it up before they closed the building in. Unless that exterior finish is something special I think it's going to crack.

Just my disorganized thoughts...

RE: Wood Guys - This a Problem?

I'm a bit late to the party here. Its been a record crazy month.

I spent a couple years around the old parts of town on the west coast doing alterations on existing timber framed buildings. They dont build them like they used to, thank god for that. I have seen timber do some pretty impressive things for an impressive amount of time.

Have seen more than a few sets of 18' long 2x4 roof rafters at 24"OC, on low slope roofs that have seen a century of winters.

2x4 stud walls balloon framed that have supported 3 levels of occupants - where the floor framing was notched 2" into the 4" depth of the stud. that have served as boarding houses/brothels/gambling dens since the 1800s.

Seen plenty of old houses where 3 levels of significant tributary area of framing will be bearing down on a single 4x4 post. resting on a 10" round rock as a footing.

None of these applications come close to meeting modern building code. But they demonstrated proof of performance.

This framing attached, even if it doesnt meet code, will survive. So long as the end of that cantilever is strapped down (which i didnt see).

And it doesnt matter how grunty your framing is, it will eventually rot out with a face sealed cladding like that shown, unless you are in the desert.



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