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As a coalminer, I used to trust my life every day to plain, round, de-barked, timbers posts, [usually spruce] 6 to 10 feet long and 9 to 12" diameter ... and I'm still here. With good cap and foot blocks these posts would still be standing when the 6"x4" rolled steel joists they were supporting were buckling under the weight of rock above. In addition, timber 'talks to you'. As a 'weight' comes on and it is getting close to failure, timber gives you fair warning

I still remember having a 15min argument/discussion in my statics and then again in strength of materials class. My question to the prof was "who came up with 1.5 or 2X as being the right safety margin? What I thought they missed in all the eng classes was a discussion about COGS or the economics of design choices. As they say, "anyone can build a bridge that stands, but only an eng can build a bridge that barely stands"

Great and interesting video! Eu citizen here, 1 inch is 25.4 milimeters which would mean 4*4 is 101.6*101.6mm

WOW! off-center consequence is phenomenal.

Besides the Euler length curve, wouldn't it be true that the longer the post, the greater the chance of there being a defect in the wood thus raising the odds of a failure?

Thank you for the video! As a builder, it's great to get a perspective on the design side of things I construct every day!

Excellent! I have been studying this type of structural member and the effects of buckling so your segment was perfect. Well done with graphics and clarity easy to see. Thank you.

Unfortunately, code assumes that the materials delivered meet the specification. Lately it seems if it looks like wood and is the correct size it passes. Cutting 4x4s out of a 6" diameter farm grown tree is nothing at all like a 4x4 quarter sawn out of a 30" log.

It's nice to see the cost of lumber plummeting to affordable levels.👍🏻💲

This all went right over my head, but it was really enjoyable to listen to. Thanks

I really appreciate that you took the time to include reference manuals, including for other parts of the world. Solid explanations and presentation. Thank you.

Thank you for that info, you did a great job presenting it!

Interesting, thankyou. I was recently talking to an Australian engineer who used to examine old trellis railway bridges for integrity. He was saying that if you had a 40x40mm column of the hardwood used in them and had a way of preventing them from buckling, then they were capable of supporting up to 70 tonne. Amazing. Of course you can't really prevent the buckling at that size, thus why the elements of the bridge are so large.

Great analysis. Love the code vs theory comparison

Subbed for the amount of effort you put in your comments. You are clearly very committed

Physicist: First we assume a perfect wood. Me: I’m using a 6 X 6. Excellent presentation, thanks.

I prefer to build-up my posts, using 2x material, using no smaller than 2x6s. 16d every 12" staggered on the faces & an appropriate adhesive between layers. This because WARPING is a reality, & using layers tends to offset that. I know, I know...that's slow & persnickety, but along adherence to Code, I build as if my own sweet Mamma was to live there :-) We Italianos have been building that way for centuries, for we love our women! Perhaps...do a vid comparing such posts with solid wood ones?!!

This is an engineering explanation of why I don't use 4x4s for second story decks. They are strong enough but tend to bow over time. 6x6s stay stable longer with the load of the deck, even though they are overkill structurely.

Found your channel recently and love it

oh what an awesome channel cant wait till i have some time to watch more!

Great to know. I am now off to cut the primary support beam in my house in two to increase its carrying capacity.

Thanks for the metric units!

I've seen them wrap concrete columns under the freeways here in California with steel and more concrete for seismic reasons. But now I can visualize the buckling and crushing forces they're trying to protect against.

That’s why I buy construction heart rough redwood 4x4s, plentiful in NorCal. The actual size is closer to 3 3/4-3 7/8” depending on the mill. They are beefy and strong. I built a 12x12’ redwood tent platform out of them with GRK 5/16 x 5 1/8” RSS Structural screws, the best

I have a beam I installed in my barn that uses triple stacked 2x8's for the posts and beam. I have yet to see it even deflect the slightest bit when I hook something up to the electric winch attached to it.

Would be interesting to see the difference in load handling when considering a 6x6 column. I'm not an engineer, but have generally had doubts regarding structural loads on 4x4s, most assuredly when length/height exceeds, say, 8 feet. Have replaced 4x4x10ft deck supports with pronounced bows, with 6x6s. No bows!

The lesson to be learned here is that it's best not to try to improve on nature. If you want to do a very interesting comparison, do a few calculations on a whole log. A vertical log, without having been compromised by cutting the natural rings, will raise many eyebrows. Minimal shrinkage (1%), maximum strength, by evolution, and a better fire rating. If memory serves, a 200 mm diameter vertical log, 2400 mm tall, will carry 20 tons. With whole log joints, in log home building, a simple wooden wedge prevents any movement in the structure, and the extra stability is obvious.

Great video my dude! 🙌

cool analysis and nice animations!

I live here in the U.S., in Arkansas. At Home Depot, a 4"x 4" square treated post is, as has already been mentioned, really 3.5"x 3.5". But...if you get a 5"x 5" square treated post, it really is 5" x 5". I think that is interesting.

For weather and rot resistance - is an end cap a good idea, or painting the end, or some other water barrier? And how often do these need to be inspected or replaced?

This video was awesome. I am a farmer. This is great info for framers to know. Please make more videos that explain wood frame engineering.

I just lifted the Supporting beam in my basement holding up 3 stories of my old Victorian house with a 4x4 post and a heavy jack. It made some strange noises but did lift the beam enough for me to make several telepost adjustments. It was a 20 ton jack and was probably near its limit.

Would love to see a chart that continues the load capacity of column at 4, 5, 6, 8, 10 meters just to see how the curve changes

Thanks so much

Excellent job. And for the Americans out there, 89mm is 3.5” and the author of this video correctly called out a 4x4 nominal dimension like we use in dimensional lumber

Please please make a similar video when the load is applied midcenter on a horizontal wooden beam. How things change when you create a slight angle, and also move the load from center to something like 1/3rd of the length. Thank you!

Thank you. Subscribed

is this why balconies fail when 15 people walk out to see fireworks

As an engineer myself, I can definitely relate to the sentiment of I love Engineering! Coding has been such an invaluable skill that I've been able to develop and see the world through a new set of eyes. Engineering is such an interesting and ever-changing field, and the sheer variety of opportunities that it offers is unparalleled. I'm truly inspired by the passion and enthusiasm I've encountered with my engineering peers. I'm sure the I Love Engineering channel serves as a great platform to showcase the limitless possibilities of engineering and it encourages others to pursue their dreams as well. Just awesome! Keep up the great work.

Very interesting!

New subscriber from Davenport Iowa 👍

There is no way I am going to understand all of this but I do have a question. If I was to sandwich plywood ( glued & screwed ) between 2. 4x2 to make one post would that be stronger than just a 4x4 post.????

I' m just an electrician but find this vidio very interesting. Maybe 445 years ago eleven decks became popular in my area home owners never got a permit or inspection for deck they installed on their houses. Most only used two 4 by 4" post to hold up a 18' wide by up to a 16' deep deck. A few years later the city sent out inspectors and made them replace fluently undersized 4 by 4" post with 6 by 6" post which have about 250% more area. A lot of these decks were built over driveway that could easily be hit by cars parked under them.

6:17 where can I find same table for cnp steel. what I want exacly like that. ex with cnp 7x3cm 1.6mm 1m length can handle load X kg

The number of people who don't know how structural lumber is sized is staggering.

Absolutely amazing 🥳🥳🥳

The thumbnail demonstrates the load being distributed on the beams below - not just the timber post. Supporting the argument: In most situations, the timber post is just for support, and the load barring can mostly come from the material of the building.

so smart calculated for 4x4 instead of 3.5x3.5

This makes me wonder whether I could use the same volume of wood in a 4x4 post of given length to hold up more weight if it were split into multiple members even if joined by only wood interlocking joints; i.e. no additional fasteners or adhesives. I feel like I definitely could for longer 4x4s especially if I don’t have to subtract blade kerf and drilled holes, but just have the final volume of wood in the structure be equivalent.

Didn't I read somewhere that wooden roller coasters are safer then steel ones.

Was really hoping to see some posts explode in strength tests, or at least some images from failed posts in the field...

So I should be ok with a 2m square playhouse built on 6 x 89x89 posts 1.5m off the floor then?

Why not explain the difference between nominal and actual dimensions, seeing as 89mm = 3.5"

Was there an explanation why a 4” x 4” post was equivalent to 89mm x 89mm? Are these “freedom” inches by any chance?

The first illustration incorrectly identifies the post as a 4inx4in while a nearby notation identifies the post as an 89 x89. The post in fact is 3 1/2” x 3 1/2” and also 89mm x 89 mm. The post is commonly referred to as a 4x4. Please correct.

Im planning to make a 20x23 ft bungalow house..6x6inches wood column 12feet in height, 10feet post to post distance in the perimeter..no post in the middle, almost a long span truss design..hope it works..

For curiosity sake ? and not for something over 6-8ft tall, will using a metal "collar" or brace, midway on a 4 by 4 or even reinforcing with a wood brace help it support more ? & possibly help "distort" the bowing ? I have worked in the trades mostly with metal But also built MANY things,out buildings from reclaimed materials! The smartest thing I discovered by accident was using rail road & sign materials were already tested to stand up to weight and wind pressures:) thanks makes me want to still be building stuff:) Rick

Excellent presentation!

So what this tells me is that almost Every deck that've seen on a hillside may fail prematurely. I see 12 ft and even 16ft 4X4s regularly, all with no diagonal supports (because those are ugly and cost more). Look out below!

I was hoping to see an actual loaded column exploding under the pressure.

What safety factor are the manuals using? I read where the ultimate strength of a SYP 2 x 4 was in the 8 ton range which makes this fir calc seem low.

And a lot more varibales. Just started the video. And non of the main points ive already considered were mentioned. Not sure if theu will be adressed later in the video or not. But, they type of tree the timber post came from is on main factor. Not all woods are the same or have the same properties and fiber structures and grain types. There are a lot of very weak, medium, and strong veriations in the wood of trees. Alao it depends on which direction of the post beam or timber you are expecting to cary the load. Trees grow vertical and are used to carrying the virtical down force of their own weight . If you use a timber as a vertical post and ypu plant it with its natural base end up then it wpnt be as strong as if you put its natural base aa the base. That working with the natural properties and how that tree the post came from grew. Also sometimes there is a big gifference in strenght of a beam as to which side is up or down and where the loads its carrying are pla ed. In most construction with post beams and timbers. The size of them far and their robustness of streanth far exccwds the application they are being used for ao builders dont pay any attwntion to these fa tors. And there are plenty of othef fa tora ro consider also. This is just a few that sprang to mind in an instant to me. Lol hope its a vauable contribution. Thanks.

The length of a TIMBER in use should never be over thirty times its minimum thickness. Thus, a 4-inch x 4-inch shore can be ten feet long, a 6-inch x 6-inch shore fifteen feet long, and a 4-inch x 6-inch shore ten feet long. If the proportion of length to thickness is greater than thirty to one, the shore will buckle ...

The old time carpenters didn't have the math skills to calculate that, but the had the necessary knowledge to know exactly the load bearing capabilities of the wood they used.

The 4x4's I buy at the lumberyard measure 3 1/2 x 3 1/2

Short version: a standard SPF 4x4 can hold aproximately 2 tons, rounded down for saftey.

I need to calculate the load of a 12 inch by 20 inch span of plywood 1 inch thick. However, I am really not sure how to mathematically calculate it with a formula.

I used to work at a glulam place called structurelam so I know about timber frame things.

I noticed the CISC steel design guide in the shots of your desk... hence I think you are likely a canadian engineer

That depends on the wood. Spruce, Hemlock, Fir, Oak, Maple, they all have different load capacity.

if you put 1/8" grooves in the side it will make it much stronger

The similarities outside of the math, to retention walls, is interesting. A shorter retention wall, is better, even if you have to stair stack them. (tier). whereas the load behind a wall, is kicking out the middle of the wall.

My house, built in 1836 uses 3x4 studs and 3x9 joist. But of course it's timber frame with huge sills, corners and plates.

If we assume complete lateral bracing, isn't a longer post stronger than a shorter post?

4" is 101.6mm - 89mm is 3 1/2". Where I live 4" is not 3 1/2". A bit like the Imperial gallon compared to a US gallon termed a short gallon. In the case of the 4" post, 25% less material, could it be called a skinny post. Cheers

It all depends what species of timber you use, and how it was grown.

Depends on length size of knotts

Stimmt alles was du erzählst.👍👍👍🇩🇪

How much wood can a wodd chuck, chuck?

A timber post CAN be used as door and window lintels as our house demonstrates

Thank,a yuo

A 4x4 (3.5”x3.5”) It’s not called a column it’s a post when it’s nailed in vertically and a beam when it’s nailed in horizontally! When it’s framed in above a door or a window it can span up to 3Ft by Code over 3 Ft you need to use a 4x6 or sister two 2x6’s together up to 6Ft. Over 6Ft - 10 feet you need two or three 2x8’s sistered together.

I always see those houses perched on 4x4's and just wonder how in the world that got approved. They're stronger than I thought, but long 4x4s still make me very nervous.

I liked you video on this, however, there is one thing I would like to point out. It might seem like semantics, but columns and posts are not interchangeable. Although you do somewhat make a distinction, the video is rather vague about it. A post is a structural element that weighs less than 300 us pounds and is either axially loaded only or is laterally restrained be a member above. A column is a vertical member that does not coincide with those parameters. The connection requirements are significant in difference, for example, a steel post requires only two bolts to the foundation wall, while a steel column requires 4 bolts to a foundation wall. There are more differences not listed in this comment, but that’s the gist of it. Our company had to change our wording from column to post on behest of our insurance company, so it does make a difference in liability.

Rot at the base of a wooden support column is a disaster waiting to happen. Water absorption from a concrete base can cause both wet and dry rot. Check your patio support columns soon.

When you design a structure such as a Covered deck you have to consider uplift from wind loads not just compressive loading. It's called TENSION. And just using Pin connections as input will produce failures. Never assume or use Pin connections in Timber Framing analysis .

Load bearing capability depends on the type of wood used, obviously hard red woods will have better load bearing than white wood such as pine.

4 in = 101.6 mm, not 89 mm, or have I missed something in the conversion?

Wood is stronger when wet, but that allows rot to occur. So wood is kept dry.

In my country (New Zealand) the nominal size for 4x4 planer gauged construction timber is 90mm not 89mm. I guess we build them stronger here. ;)

6:00, for viewers inside of North America, 1 inch is equal to 25.4 mm, meaning 4 inches equals 101.6 mm

Cool video. Seems like you have spammers in the comments.

A 4x4" isn't 89x89 mm, it's 98x98 mm. 4" is in reality 101.6 mm, but international standards says 98x98 mm dimension. Leaving 2 mm for adjustments up to 100 mm. But if your 4" is actually 3.5" it's a different matter 😅

4inchby four inch is 25.4mm per inch is more equivalent to 100mm x 100mm

As a carpenter for 47 years, loads are influenced by clear wood, knots,and defects. Also old growth or today's garbage. And of course species of wood. Hardwood, softwood. Also where said tree grew,hillside or flat land. And twist in trunk or straight growth in trunk. And lastly cut of the post.

Depends on the timber - a fast grown less dense wood will hold significantly less and for shorter time than a slow grown dense wood of the same species.

Column?

The one thing every formula can not foresee.....TIME AND VARIABLES