Review of basic geometry, Pythagoras' Theorem and Similar Triangles, needed for roof calculations
Пікірлер: 159
@MichaelDavidHiltner9 жыл бұрын
I'll be building a 12x18 shed to join to my existing 12x12 shed (will remove the sheathing from the joining side), remove my existing roof and tie it in to my new shed, later this spring. This has been extremely helpful for my understandings. Thanks Professor! This is what I use the internet for!
@glennunderwood46907 жыл бұрын
Very nice explanations and drawings. ..thank you for your help. Clearly shows the need for math skills and some knowledge of building.
@montaguechristian110 жыл бұрын
Great break down. Thanks for the informative tutorial.
@tammyghashghaie34069 жыл бұрын
Dear professor amazing and informative lecture truly Tammy
@michaelnauth9 жыл бұрын
Thank you Tammy
@tammyghashghaie34069 жыл бұрын
i will look forward to watch more of you video by the way your tone of voice makes audience to understand and follow you more
@allamericanhandyman76339 жыл бұрын
Detailed explanation. Worth watching!
@KennethDFranks18 жыл бұрын
Great math lesson with practical uses of Pythagoras' Theorem.
@michaelnauth8 жыл бұрын
+Kenneth Franks Thanks Kenneth
@jrquidi25723 жыл бұрын
I love it .... learning is the BEST way to get to be the best in subjects
@flankerroad74144 жыл бұрын
Great video offering detailed insight on the math of cutting rafters...the better grip you have on this the more confidently you'll approach your work.
@michaelnauth4 жыл бұрын
Thanks Jacob
@bobalicon10003 жыл бұрын
Finally after looking over 20 videos I found this one that I understood how to measure and cut the rafters properly.
@michaelnauth3 жыл бұрын
Excellent!
@MariaSearsmercy139 жыл бұрын
Explained well. Even if ones math skills are rusty. Thank You.
@robindevellen70384 жыл бұрын
Maria Sears if I had math skills to begin with🥴
@unclemony59394 жыл бұрын
Hello professor, ur lecture is impeccable, BUT!! Simplicity is what I live for. I have paid dearly, but mastery is never too far around the corner.
@BushcraftPaolo4 жыл бұрын
Clear, polite... Perfect! Tanks a lot.
@michaelnauth4 жыл бұрын
Thank you.
@machia07055 жыл бұрын
Good lecture professor , but I can do all of this with a pencil and my tool belt. A circular saw and a T-square on the bench too. As for design work, I have a book of tables . However your in depth look at this and explanation are impressive. Great presentation.
@timbarry50804 жыл бұрын
That's why its easier to measure your span and run from the inside of the top plate rather than the outside. This way your measuring line is on the bottom edge of the rafter than being inside the width of the board. And your measuring line ends right at the edged of the ridge board instead of its center. Don't forget to subtract the thickness of the ridge from the span before calculating the run..
@markpenn48316 жыл бұрын
Very clear and concise ! Many thanks...
@michaelnauth6 жыл бұрын
Thanks Mark.
@gabrielgonzales81636 жыл бұрын
buenos videos construccion #1
@AFFarms4442 жыл бұрын
Superb explanation! Thank you.
@mariosioannou43468 жыл бұрын
Hi Michael, I found your lecture very interesting and informative. I think its good to explain fully how it all works. I, personally, will remember this lecture and put it to good use in the future. I just have one question at 18:13 onwards where the small triangle at the top shows a ratio of 1:1.5 re the slope. Is this a mistake or maybe I'm not fully understanding this. Can you please clarify?
@michaelnauth8 жыл бұрын
+Marios Ioannou Hi Marios In the Canadian Building Code the roof slope is given as a ratio relative to a rise of 1(Metric or S.I.). So a 1:1.5 roof slope is the same as 8:12 in Imperial terms and also the same as 150:250 when using the Metric (SI) framing square. Good catch - I forgot to note that. First guy in 351 000 to ask that.
@naturalmystics-kd9vt3 жыл бұрын
Mr Michael nauth thank you for this video I learn a lot from you video you are a good gentleman and a good teacher I thank you
@michaelnauth3 жыл бұрын
You're welcome.
@calbinoIa9 жыл бұрын
I used to cut roof rafters for framing conventional roofs with a calculator also and then built them. I understand how to do this, but after listening to you explain this I see why I hated math in school. Sorry, but while this is an excellent explanation, it is dry enough to put me back to sleep.
@wallacelux5 жыл бұрын
Ungrateful.
@arturovarela83955 жыл бұрын
I felt like a was back in high school too!!! I rather skip class and go take 3 lunches!!!
@someonespadre4 жыл бұрын
I'm building a small shade structure. In order to figure out how to frame the roof I watched carpenters on KZbin with their speed squares and their framing squares and their construction master calculators and figured out all the pieces and parts then, like this guy, I sat down with paper and pencil and broke down all the little triangles. It's all just Pythagorean theorem or simple proportions, don't really need trigonometric functions except to calculate angles for a miter saw. Then I did it again in my cogo (coordinate geometry) software to confirm my numbers.
@michaelnauth4 жыл бұрын
You're correct David. It's simple geometry.
@emilyeilene9 жыл бұрын
Thank You for making this!
@kenjimrankin74857 жыл бұрын
hi useful refresher worked out roof in 15min thks, however i could have did it on the computer in 2min, and got my purlins sized into the bargin.
@Chevy-ud1ec7 жыл бұрын
how did you come with the number 15Thanks Harvey
@davido30263 жыл бұрын
Excellent including Metric equivalences!!!
@michaelnauth3 жыл бұрын
Glad you like them!
@samanthayau31416 жыл бұрын
thanks for showing. It is a very tutorial, educational video. I built a roof and did the calculation. The rafters always came off a bit and could not fit right in. The problem is the rafter with a birth mouth that accutally sit two inches or whatever inches inside from the outside walls. You have mentioned about this problem by dropping the ridgeboard height. Can you explain to me how you get a 3/4? And why use 16 as a base when calculating ridge drop (x)? And what did you mean by cut/left on the flat? I am not sure i got it. Appreciate any help.
@michaelnauth6 жыл бұрын
For a roof that has a 7 in 12 slope, 7 is the rise (vertical) and 12 is the run (horizontal) . You would compare it to a similar triangle that has a run (base) of 3/4 of an inch or one-half the thickness of the ridgeboard. So the vertical (rise, r) of the small triangle would be found using ratios: r ÷ (3/4) = 7 ÷ 12; r = 7 x (3/4) ÷ 12 ; r = 7/16 . If the ridgeboard is 1½" thick then, the drop for the ridge is the unit rise (in this case 7) over 16. This works for any roof slope as long as the ridge is 1½" thick. An 8/12 slope would have an 8/16 drop or ½".
@samanthayau31416 жыл бұрын
Thanks so much of your information. Appreciate so much. I am not in this trade. But i love to build and design houses.
@SuperCyril24 жыл бұрын
Remember to add on your overhang to your rafter length.
@jonienglish32313 жыл бұрын
Michael @17.37 - X Calculation getting to Technical just say the 5ft + HAP 4 1/2 - Ridgeboard Width = the Actual Height for the Ridgebeam Pending the Width of the Ridgeboard .
@charlesgreen2394 жыл бұрын
Very well explanation of the geometry. I still did not see how you calculate the rafter stand or HAP? You had 4 1/2 on the drawing.
@michaelnauth4 жыл бұрын
Hi Charles Sorry it took so long to reply. I started to and then thought that a diagram would make it easier. I still haven't figured out how to post a diagram in the comments section. Well, here goes - in words. I had just stated that the Stand was 4½", I did not calculate it, but I measured it after the birds mouth was laid out. To calculate it, you would use Similar triangles and Pythagoras's theorem. First, to get the length of the plumb cut on a 6 in 12 sloped roof (1:2), draw a Ridge Plumb Cut line on the end of the 2 x 6 rafter and you will form a right triangle that is 5½" on on side, 2 3/4" on the other and the hypotenuse can be calculated using Pythagoras to get 6 1/8" [or you could just measure the plumb cut line]. Second, setting the horizontal Seat Cut line at 3¼", the Heel Plumb Cut line would be a half of that or 1 5/8" (again because it is a 6/12 roof slope). Subtracting 1 5/8" from 6 1/8" gives you 4½".
@Koumondji8 жыл бұрын
wow, this is a lot of Math. Good knowledge tho, I just cannot keep up, lollll
@LouieHarmston8 жыл бұрын
+Angelo Koumondji, lol don't even try to, this is useless information..
@majorkonfuzion10078 жыл бұрын
+Angelo Koumondji me too my head is spinning.
@ArtisanTony6 жыл бұрын
It is really not this complicated. It is basic math and can be done in seconds mostly i your head. You just need a basic calculator that does square root which every calculator does.
@omarcortez59625 жыл бұрын
Easy way kzbin.info/www/bejne/mWW1pYGhmK2SlbM
@juginstr10196 жыл бұрын
Great video!.Thanks a lot.
@gregwarner37534 жыл бұрын
All of these calculations can be done on an old fashioned framing square . All you need is a set of instructions .
@defy25984 жыл бұрын
Yes but this is only the beginning this math builds on its self alowing you to do octagon Pentagon and any other gon roof
@unclemony59392 жыл бұрын
@@defy2598 🤣🤣🤣
@zero000444 жыл бұрын
Seems much easier to eyeball everything. Didnt understand half of this because things like trigonometry and calculus arent taught in all high schools and never in the basic math classes. Just the optional classes. Heck, I dont even know what trigonometry and calculus are. Most we got was algebra and I dont remember 99% of it lol.
@mrreason96975 жыл бұрын
I'm really struggling with the rafter stand part ad the actual length, done some practice cuts and keep screwing up
@michaelnauth5 жыл бұрын
Hi David I am not sure how to help. Maybe you can give me the dimensions of the building and the slope of the roof and the lumber dimensions so that I can respond in context.
@jonienglish32313 жыл бұрын
@17.00 Michael is making it Confusing Ridgeboard STAND = Total Rise + 4 1/2 ( HAP) then Subtract Width of Ridgeboard ( 2x8 or 2x6)= Ridgeboard Stand
@hillcountrygarage8 ай бұрын
Very, very informative and helpful. Two questions: how important is it to subtract the ridge drop from the actual rise calculations? Wouldn't the total rise plus the rafter stand calculations be sufficient for most structures?
@michaelnauth7 ай бұрын
The subtraction is mainly a test for carpentry competitions where the ridge is flat on top (a standard 2x6) as opposed to one that has been bevelled to a peak.
@michaelfahandez50423 жыл бұрын
Thx u sir godbless clever made it easyer for me
@michaelnauth3 жыл бұрын
Thank you Michael.
@roxydog-db1pu6 жыл бұрын
If This Old House talked about this it would have lasted about two episodes
@ebroevets95429 жыл бұрын
I think I'm just going to steam bend some long boards into shape...hehehehe then all I have to do is cut the birds mouth on them.
@blueXRPdynamite.6 жыл бұрын
OOOOh. If only i was intelligent. Life would be so much easier..
@foobar31393 жыл бұрын
You’d think so...
@Valentina_-lw9ui3 жыл бұрын
Winner of a video, been searching for "what is the maximum span of a roof truss?" for a while now, and I think this has helped. Have you heard people talk about - Beybigail Nonpareil Breakthrough - (search on google ) ? It is a good one off product for discovering how to create better sheds and improve your woodworking without the hard work. Ive heard some amazing things about it and my cousin got cool results with it.
@neilarreola78418 жыл бұрын
Just draw the truss diagram in autocad, right click on any line to show its properties and the length will be given. No need for calculations.
@ricardomontalvo9638 жыл бұрын
+neil arreola Haha, yes super easy, but not everyone has that soo the old school way is the way to go
@JohnzeeMr8 жыл бұрын
Leonardo De Mao: Very nice finding the length of the rafter is exactly what children who do child's play need to get into mathematics, if I was a kid and got hooked into the practical application of triangles and somehow become aware that it is my social responsibility or necessary for a bright future then transitioning into more complex mathematics would have been a breeze if I learned the basics. Individual buildings may be child play but imposing structures have complex mathematics build into them like take into account the ever important but not visible sway of tall buildings as a result of wind, new materials have to be developed and chemistry comes into play to test the elasticity of various new substance made. Most people are good at climbing and hammering and it takes a lot of their brainpower to have no time to dream but a very few who just have enough experience as a carpenter or an excellent craftsman will have imagination to create innovation and an entire civilization will depend upon this people for its survival and prestige, Edison, Newton, Einstein etc, including the ultimate personification of cuteness the Supreme Leader Uncle Kim Jung Un.
@jimmy21480_midnight_special8 жыл бұрын
what the??
@brentstarkes96822 жыл бұрын
Well done!
@michaelnauth2 жыл бұрын
Thanks Brent!
@germaniumoxide63827 жыл бұрын
Are you Mr. Smith from the Matrix movie..!!!!!????
@sbk1627 жыл бұрын
can you do your calculation without using calculator
@michaelnauth7 жыл бұрын
To find the hypotenuse of a right-angled triangle you can use the framing square and similar triangles. For instance, locate 5" on the tongue of the square and 12" on the body and measure from 5 to 12 and you will get 13" which is the square root of 5 squared + 12 squared. Also this number is etched on the framing square on the body under 5". You would then take the RUN of the roof in feet and multiply it by the 13" and that will give you line length of the common rafter from the centre of the ridge to the outside of the wall which is where you will cut the birdsmouth of the rafter.
@sbk1627 жыл бұрын
thanks for the info
@nilsbruhner19836 жыл бұрын
Sketchup
@addaimartin62373 жыл бұрын
I like the way you are teaching
@michaelnauth3 жыл бұрын
Thank You Addai.
@HsingSun3 жыл бұрын
What do they call "side by side triangles" under both sides of roof rafters?
@michaelnauth3 жыл бұрын
Not sure - together they form the Gable End.. Each one is a mirror image of the other.
@TR-rn3pd3 жыл бұрын
Can you or someone tell me what the hip/valley line length ratio “secant “ is of a 5/12-8/12 bastard roof is . I don’t know if I’m doing the math correctly or not.
@michaelnauth3 жыл бұрын
When calculating rafter lengths for an Unequal Slope Hip Roof, all measurements need to be made to the fascia line in order to maintain an equal projection on all sides. For the roof in question, let's call the 5/12 side the 'Side Roof' and the 8/12 side the 'End Roof'. For a Side roof run (to the fascia line) of 2' or 24", the rise would be 2 x 5" or 10". Therefore the End roof rises a total of 10" with an 8/12 slope and thus the End Run is 10" x 12 ÷ 8 = 15". The Hip or valley rafter then has a run equal to the hypotenuse of the 15/24 triangle or SQ Root of (15 squared + 24 squared) or 28.30". But it still has the same rise of 10". The length of the Hip/Valley rafter would then be SQ Root of (10 squared + 28.30 squared) or 30.01". [you can skip a step and take the SQ Root of (15 sq'd + 24 sq'd + 10 sq'd). The Hip angle is found by taking the INV TAN (ARCTAN) of 10 ÷ 28.30 or 19.5°. You can also take the ARCSIN of 10 ÷ 30.01 .
@TR-rn3pd3 жыл бұрын
@@michaelnauth when calculating the run for the unequal slope hip. Do we use the run of the shallow side or the steep side.
@michaelnauth3 жыл бұрын
@@TR-rn3pd When calculating the rise for the Unequal Slope roof, you would use the run of the shallow side, measured horizontally from the fascia line to the centre of the building.
@TR-rn3pd3 жыл бұрын
@@michaelnauth made sense to me after reading your last comment a few times . Thank you for your help.
@00skeletor004 жыл бұрын
You can enter into the calculator 4sq + 3sq =25 2ndF sq = 5
@framingvagrant Жыл бұрын
Simple. Thanks pal.!
@michaelnauth Жыл бұрын
Glad it helped
@moods51144 жыл бұрын
You have to come with some practical examples its difficult for new learners , like you have to out values and calculate
@michaelnauth4 жыл бұрын
Check around 21.00 mins on the video.
@jackf4984 жыл бұрын
how does the .839 get converted to 10in 1/16?
@00skeletor004 жыл бұрын
Jack F .839 x 16 = 13.424 or 13/16 not sure where the 10 1/16 comes from...
@michaelnauth4 жыл бұрын
. 839 ft. x 12 = 10.068", .068 x 16 = 1.09 which rounds to 1, hence we have 10 1/16"
@thakery57203 жыл бұрын
So now I know why I was taught trigonometry....... still haven't found a use for algebra though........
@michaelnauth3 жыл бұрын
Solving similar triangles is algebra in action. Anytime you use 'x'.
@felixgonyo18093 жыл бұрын
Thanks for your teaching
@michaelnauth3 жыл бұрын
You're very welcome.
@glennunderwood46907 жыл бұрын
The outside of a birds mouth does not sit flush over the sheathing, it sits flush over the top plate...😊
@russelleldridge37267 жыл бұрын
And then your notching he plywood around every rafter?
@glennunderwood46907 жыл бұрын
Some framers I've seen run the sheathing up to the the rafters, some up to the soffit nailer, I've never seen birds mouths' up against sheathing, Although after thinking about it, it's a good idea To not have to cut the sheathing to length. Unless you live in an area with high wind loads And have to install hurricane ties, which would have to be inspected before sheathing goes on. That being said....thanks for the input, and your Drawings, they're very nice.😊
@russelleldridge37267 жыл бұрын
glenn underwood I always have sheathed walls and stood them up and then install rafters.....or I'll add an extra 1/2nor 5/8" to the seat cut so I can slide plywood up if the rafters are already installed
@mohamedissakamara61423 ай бұрын
Thank you Sir 🥰
@JoseSanchez-xd1oz7 ай бұрын
Thanks Michael
@okusitinotahitua10207 жыл бұрын
sounds academically steps by steps , the other carpenter don't know how to add 2 + 2
@elfantasmadeatx88074 жыл бұрын
I don't get how you get to 3/4 (19) from 12 ?
@michaelnauth4 жыл бұрын
3'4" (19 mm) is one-half the thickness of the ridge board, which is 1½" thick.
@simonrosoery9467 Жыл бұрын
how do you work out A ? total run is 4940m which is B . Trying to work out A on a 12 12 pitch roof?
@michaelnauth Жыл бұрын
Not sure what you mean by 'A'. For a 12 in 12 roof, the Total Rise is equal to the Total Run.
@cb-vp5gp4 жыл бұрын
from where the 3/4 (19)?
@michaelnauth4 жыл бұрын
3/4" (of an inch) is 0.75 inches or 19 millimetres.
@jrquidi25723 жыл бұрын
👍😎
@MH-qg1ky4 жыл бұрын
So basically if you take trapezoid and a triangle and smack them against the wall it will turn into a circle. Is that what you're saying????
@michaelnauth4 жыл бұрын
The trapezoid plus the triangle together make a Rectangle.
@MH-qg1ky4 жыл бұрын
I was just trying to be funny dude
@leoayoroa72172 жыл бұрын
Good stuff
@michaelnauth2 жыл бұрын
Thanks Leo
@mafirearmsafety7 жыл бұрын
Gads! I don't feel like any of this is 'simple'......
@guillo23886 жыл бұрын
You can bypass all the time-consuming math by using any drawing program and or using a Speed Square
@hillcountrygarage8 ай бұрын
Or you can take the time to understand the geometry behind the calculation and have a better understanding of the construction. Lazy and stupid is no way to go through life.
@brianfield7924 жыл бұрын
Does measuring and cutting roof rafters have to be this difficult,I think not, get a good roofing square, read the numbers imprinted on the square,or learn how to read it, it will give you everything you need to know, including rafter length of any pitch down to the birdsmouth,
@michaelnauth4 жыл бұрын
True - just follow the correct steps.
@gerrigerbils14137 жыл бұрын
I still don't understand
@JoseSanchez-xd1oz7 ай бұрын
Good class
@MedelGeorge7 ай бұрын
Very helpful thanks
@michaelnauth7 ай бұрын
You're welcome , George.
@addaimartin62373 жыл бұрын
And the professional carpenter know that they knows everything but not yet every day new are coming
@benl16123 жыл бұрын
can you please do one with millimeters instead?
@michaelnauth3 жыл бұрын
Hi Ben I will work on an SI version (mm) and post it ASAP.
@michaelnauth Жыл бұрын
Hi Ben (sorry for the late reply). In the SI system, roof slope is stated as Rise : Run, but with the Rise being '1'. So a 6/12 Imperial roof slope would be a 1:2. Using that ratio, and Similar Triangles, a roof with a span of 8m (run of 4m or 4000mm) and a slope of 1:2, would have a Total Rise of 2000mm (or 1/2 times 4000) and a rafter length of 4472.1mm (√(2000² + 4000²)). For the same roof with a slope of 1:1.5, the Total Rise would be 2666.7mm (1/1.5 times 4000), and a rafter length of 4807.4mm (√2666.7² + 4000²)).
@davidgentile45764 жыл бұрын
how about just laying it out on the slab itself. little math and actually gets done quicker
@michaelnauth4 жыл бұрын
Works well also.
@carpentryzucconiltd78753 жыл бұрын
Why making things complicated. In ancient carpenters brotherhood calculations, we calculate hypotenuse using your given run measurements Multiplied to the secant at your given pitch and that's it. Example your run measurement is say 345.8 cm and the pitch is 45 degrees, just do 345.8 X 1,4142 ( secant number from periodic tables at 45 degrees ) equal 489.03. that is exactly your hypo. However good lessons for beginners it yours.
@mickmac33602 жыл бұрын
There is no need to calculate the length of rafters and framers will not be interested in getting into the math. All you have to do is mark run and rise at right angles on the flat, put the rafter in correct position with respect to wallplate and ridge and mark as required.
@valhallanews5675 Жыл бұрын
What if you have a tall building with long rafters? Are you gonna climb and place 6 meter wooden studs at 10 meters above the ground while your assistant applies a tape measure? Don't be a fool.
@jaferalmoosawi61163 жыл бұрын
Thanks
@michaelnauth3 жыл бұрын
Welcome
@russelleldridge37267 жыл бұрын
I thought your video was awesome. I see a lot of people complaining and it's obviously because they only know how to do one thing. Take away their rafter book, and square and they are lost. I wanna see calculations for rafters with a ridge already set. How would you do that?
@Redandranger6 жыл бұрын
Just subtract half the width of your ridge beam from the horizontal measurement of "B" before you use it in A2 + B2 = C2
@edwardcharles97645 жыл бұрын
This is a math lesson nothing more.
@chamroeunsdoeung44224 жыл бұрын
I'm not good at math, this video is not for me.
@nguyenhiep5803 жыл бұрын
This was great, thanks, I been tryin to find out about "how to build rafters for a shed" for a while now, and I think this has helped. You ever tried - Beybigail Nonpareil Breakthrough - (just google it ) ? It is a smashing exclusive product for discovering how to create better sheds and improve your woodworking minus the normal expense. Ive heard some great things about it and my brother in law got great results with it.
@atv5580311 ай бұрын
4+3 =5 no it doesnt its 7
@microtrance12343 жыл бұрын
Many thanks, I have been researching "how far apart should rafters be on a shed?" for a while now, and I think this has helped. You ever tried - Beybigail Nonpareil Breakthrough - (should be on google have a look ) ? It is an awesome one of a kind guide for discovering how to create better sheds and improve your woodworking without the normal expense. Ive heard some awesome things about it and my co-worker got excellent success with it.
@marauderconvoymcoc42597 жыл бұрын
If you Really want to learn about how to build a Roof - please look up the best " Larry Haun" Seriously - I fell asleep watching this video - then woke up and still the video was on when I woke up. Learn to teach - no disrespect to the author 😬
@jeremyfoster69426 ай бұрын
There are plenty of apps and ready reckoner books that do all this maths for you, even a basic knowledge of how to use a framing square will do the trick, this is archane and pointless