How to work out rafter lengths for different height wall plates***UK ROOFING CARPENTRY/FRAMING***
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- Опубліковано 12 тра 2023
- In this short video I show the simple method I use to determine the rafter length when pitching onto different height wall plates.
I always watch your videos, even if I can't understand what you are doing. LOL
That's very kind of you Randy🤗 Cheers Del
Yes, so do I! I guess a few of us agree!
Very clever. I have never done it that way. But if you know how. It works. Follows on nicely to a comment I read on another UA-cam channel. A guy had written regarding learning maths essential at school for being a Carpenter. The basics yes. Got to watch your wages. I have never been a calculator. Most of the old guys who taught me weren't either. The guys that built the complicated old Cathedral and Church roofs were mostly uneducated. They probably got their measurement with a piece of string. Currently in Australia there is a massive shortage of all trade type skills. A Senator recently suggested that we start looking back and release kids interested in these trades early, as they used to. Instead of trying to force everyone to complete school. Go to University. And join the dole queue. Or start learning a trade, when you could have been qualified. You have the best of both. You have the smarts and the hands on skills. But less bright people with common sense and training can still make good Carpenters. Not a lot of schooling required.
Hi Dave🖐It frustrates me that I cant have a proper, face to face, conversation with you about this, and feel that responding in text will never due the subject justice😩 All of what you say is correct, and we are heading for BIG problems in the next 10 to 15 years as the last of the generation who's parents encouraged them to get a trade, slowly retire😬 Great comment as always bud👍Cheers
Gotta luv a traditional roof, the things that you learn are invaluable. Gr8 video mucka
I do enjoy traditional, hand cut roofs Steve👍like you say, there's always things to learn😎Cheers Del
Hey Del. Really good explanation.. Dave Taylor (ahead of me) makes a cracking point about calculation. all the old guys I worked with were NOT mathematically good but time serving, watching and gaining experience as they went along. Grammar school education was just not working.... many, like me passed 11plus but as we had no certificate and were just told we could or could not attend Grammar school we just went to local Secondary Moderns as directed.... 18 to 20 percent of kids did not get "the chance" due to home life, parental income etc. or even worse living in a council house were thrown into the mix! I was told by my original teacher that I had passed but due to "the system" did not have that chance. She told me in 2005 ( my 11 plus was '64/'65. As time went by it was realised that I was discalculate but managed years in the aircraft Industry and then building trade by experience and care for "the product". I feel that our education has been let down by what was really a "social experiment" not a planned attitude to what the country needed. Rant over and thanks as usual. Bob (Weston super Mare)
Hi Bob🖐As I said to Dave, I'd love to have this kind of conversation in person, as everything you say is spot on, and the reason we are now in a very dire situation with the lack of youngsters in ANY, vaguely, manual type jobs😬 Our education system, and wider society in general, needs to understand that a lack of academic achievement does NOT equal a lack of intelligence🤔Thanks for taking the time to watch and leave your great comment😎Cheers Del
Cheers for sharing Del 👍👍👍and making easy sense 🙏
I'm glad you understand it John😉Thanks for your comment🤩Cheers
As always T.C. A great explanation of your carpentry skills to the layman like me ‘ keep up the great work and videos 🔧🔧👍👍😘
Hi Brian🖐I always appreciate your comments bud, and you even blew me a kiss, which I have caught, and will return😘😆Cheers Del
Brilliant explanation thank you 👍🏻
My please Matt🤩Thanks for watching 😎 Cheers Del
Understood! Loud & Clear!
Nice one GL🤗
Hi Del Great explanation , some times I use the tangent on my calculator to find the difference but if the batteries go down i go back to the framing square and set like you did. thanks for a great video.
You're spot on about using a calculator as well to work this out Peter👍I also use a simple right angle triangle calculator app, that I could just put in half the drop, (opposite), the pitch, and it then give me the the amount to reduce or extend each rafter. (hypotenuse)👊
Well thats made my day as i actually grasped all of that 😆😉👍
I'm not surprised Andy, and I'm glad you got it🤩Thanks for watching fella👍
@@thetallcarpenter 👍
Great video !!! 😊😊😊😊😊😇😇😇😇😇
Thanks for watching Michael 😎
My boss and I here in Perth, Australia, use a mathematical calculation that we figured out to work out our rafter lengths when pitching down to different plate heights, it must be the easiest method as you are just given 2 seperate lengths on a calculator and don’t have to mess around with marking the rafter as you showed here - which is still awesome as I had never seen that method so thanks for that! Anyways, this is the formula, you should give it a shot as we have pitched 100’s of roof’s to different plate heights using it without fail!
So you need to know:
1) your rise constant and rafter constant for your ° of pitch
2) the vertical height difference from top of one plate to the top of the other
3) and lastly you must know your full span/run from outside of low plate to outside of high plate (pitching lines)
The first step is to DIVIDE the plate height difference by your RISE constant, as we know the VERTICAL measurement from top of plate to top of plate so by doing this it now gives us the HORIZONTAL run difference, the way we get the different rafter lengths is by using seperate half spans (rafter runs) to work out the lengths. To do this, you now get your full span/run, add the horizontal difference measurement we just attained to it and divide it by 2. This will be your half span for the longer rafter to the lower plate hence why you added the difference. Now to get the half span for the shorter rafter you simply minus that same horizontal distance from the full span/run and also divide it by 2, this will be the shorter rafter half span that goes to the high plate. Now finally, with these two seperate spans, you can go back to basics and simply minus half the thickness of the ridge (if using one) before multiplying your half spans by your rafter constant for your lengths. I feel as if I just wrote an essay to explain a simple way of doing something, but trust me it’s easy! I’ll do a quick example if it helps?
Let’s say we are working with a 35° pitch (700mm of rise per 1m of run, and a 1.221 rafter constant)
We have a full span from pitching line to pitching line of 6000mm
And we have a plate height difference of 300mm from top of plate to top of plate. Calculations would go as follows:
300 (plate height difference) -•- .7 (rise constant)
=428.6mm
6000 (full span) - 428.6 -•- 2
=2786mm this is your is your short rafter half span.
6000 (full span) + 428.6 -•- 2
=3214mm this is your long rafter half span.
2786 x 1.221 (rafter constant)
=3402mm this is your short rafter length!
3214 x 1.221 (rafter constant)
=3924mm this is your long rafter length!
Let me know what you think @thetallcarpenter, this method also allows you to find the ridge position prior to pitching as you have the separate half spans/runs for the different rafters.
Hi Marcus🖐Great to have you watching from down under🤩and I really appreciate you taking the time to explain another cool way to find the differing rafter lengths👊I'm pretty sure I follow what you're saying, and will be trying it out the next time I'm on a split plate height roof👍One of the best things I've found since posting videos on UA-cam is how we can all share the ways we do things, which just makes us better and more efficient at our trade👌All the best(and for your Wallabies up here in France😶) Del
This is awesome Marcus👊 I'll be giving you a shout out if I use your method in any future videos😎Cheers Del
nice one buddy. also when i have the guide rafters set up i mark the soffit cut that way because the plate is level they will all be the same and you can cut them all on the deck which is much easier. then when its all pitched you only have to do the cuts for the facia.
Hi there🖐 That's a great idea, and, as you say, saves having to do the rafter foot seat cut in situ👍 My problem is, I never actually know exactly what the soffit detail is until the roof is on and I've gone over it with the builder/customer🙄Thanks for watching and your comment😎Cheers Del
Great explanation Del. 🙌🏻
👊🏻
Cheers Dan🤗Appreciate your comment bud👍Cheers
Dan, your roofing square, Can it be used by left-handers, by plumb cut on the left or is it set up for the convenience of right-handers. Thanks
Hi @@gavincollins9376 , the square isn’t universal and only works one way. It’s not so much set up for right handers however it’s more working down the rafter on one face. I work with a left handed chippy at time , and he uses one. As I know you’ve seen my videos, you can see I cut the plumb cut then measure down.
Any other questions please fire away. 🙌🏻
@@Ultimate-roofing-square. Thanks, Dan for the reply.
Excelente trabajo 👌👍🧱
Thanks you Vianka 🤩
👍well explained
Thank you Paddy🤗Cheers
As always. 👏👏👏👏👏👏
Thank you Alistair🫡Cheers Del
Thank you for sharing
No worries Martin🤩and thanks for watching😎Cheers Del
Good tip 👍
Cheers🤩Thanks for watching 😎
Thanks del👍
You're welcome 🙏 EJ🫡
👍👍👍Thank you.
Cheers Pete👊
Outstanding Del, 👍🔨🇮🇪
Thank you TN🤗I hope it makes sense🤞Cheers
@@thetallcarpenter That's a good way of doing Del, there's a few other methods as well. More than one way to skin a cat as they say. It looks like you got the weather for it anyway, don't forget you hat and sun block, 👍😁🌞🔨🇮🇪
@@TheToolnut I did this roof about a month ago no TN🤯As soon as the clocks changed, its gone all wintery again🥶Cheers
@@thetallcarpenter 👍😁🔨🇮🇪
@@thetallcarpenter ua-cam.com/video/IA-riDdC3Ak/v-deo.html.
🤘😎🤘
Top man you mate, defo need your help on a few jobs 😂😂
Cheers Ashley🤩Thanks for your comment 😎
👍
🤩😎🤩
We’ll explained del top man 👍🏻
Cheers John👍and thanks for watching
I just did a massive hand cut roof, with different roofs all meeting and this was the case on part of it, but it was coming off the existing roof, i took measurement from ridge to wallplate for rafter length then straight edged off the existing for birds mouth depth as the part i edged off was creeper rafters on the valley rafter,, if you can get what I'm saying😅😂😂😂
I get what you mean Stephen, and on many occasions like that, running the level over existing rafters is the best way to get the right measurements👌 Your roof sounds like fun🤩Cheers Del
@@thetallcarpenter well dunno about fun lol, not a kick in the ass of 60,, 🤣🤣 the body is slowly but surely saying no, but i do love roofing, so I'll carry on for now 😜😂
Hi Del was it just luck that when you marked the 1st plumb cut, and swivel your tape down the line 195mm that it hit the bottom of the timber exactly, from where you squared back for the 2nd plumb cut. This being the shorter rafters true length ? On that roof the true run is outside of wallplate to face of double ridge you birdsmouth over yes ?
Yes Kevin, it was pur luck that the plumb cut was exactly the same as half of the plate height difference😉And yes, the true 'run' of the rafters is from the outside of plate to the ridge. (be it minus half the ridge board or not in my case). All the method does is gives you how much, either longer or shorter the 'run' is for each side without having to actually work it out. (it's basically the seat cut line I drew from the 195mm down back to the top edge of the rafter)👍Cheers bud
Sorry Kevin, I just re read the last part of your comment, and NO, the true run of the rafter is from the outside of wall plate to the RIDGE plumb cut. (I didn't deduct the ridge thickness from my 'run' calculation as the rafters meet each other and not either side of the ridge, they are only sat 'on' the ridge, and not 'in' it) I hope that makes sense🤞
@@thetallcarpenter It was basically half the span of outside of wallplate to wallplate then.
@@amazing451 Spot on Kevin👌andcI wish I could have had more time to go through that in the video, but as usual, I have to crack on🫡
@@thetallcarpenter OK mate hope to see you soon 👍👍
So in the scenario where you cant mark the divide of the plate difference on the 6x2, what do you do. Say the plate difference is 600mm
Great question bud👌and, in the case of the video, it was fortunate that half of the difference in the plate heights wasn't a greater measurement than the length of the plumb cut👍But, if half the drop measurement was longer than the length of the plumb cut, as you suggest, I would simply tack a short length of rafter material under the rafter and extend my plumb cut down onto it the 300mm and then square/level across as per the rest of the video👊 Also, be super easy if you used a framing square to do your roofing as you'd just read straight off it😎Cheers Del
Is it easy to have different level wall plates but still get connected to an existing roof? Not much information I know but I doing an extension are the current ceiling height is quite low so would good if I can increase it on the extension section
Hi there🖐Yes, it's easily possible to connect one roof to another in this way when the ceiling heights are different👍You may need to keep an eye on the valley line though to make sure there is a stub rafter far enough back to catch it👊Cheers Del
@thetallcarpenter I was thinking to get a truss company to design the trusses which in theory should be easier as they should design it accordingly?
@@sajhussain26 I'd imagine any decent truss designer will be able to come up with a split plate level roof👊
My builder has told me we can't have different hight wall plates and that he needs to follow the hight of the crack beams which now means my facia boards not lining with my nioughborys house! And
Hi there🖐It would be unfair of me to comment on what you're builder has said/done without seeing what he was faced with🤔As you can see from my video though, you can have different plate heights👍Cheers Del
What's the rule for putting up all the overhead covering? I see lots of that in England. Must send cost through the roof
Hi there🖐The roof structure typically has a breathable membrane fitted, then 2x1 tile 'battens' fitted running the length of the roof, these are spaced anywhere from 4" to 10" depending on roofing tiles/slates, and finally either slate or concrete tiles are nailed to the battens overlapping from the bottom up.
I guess it's more expensive than 1/2" sheathing and bitumen shingles, but the roofs, pretty much, last a lifetime👍Cheers Del
Is there an easy way to work out plate height if your new rafters are 6x2 and you're extending a roof made of 4x2 or 3x2?
Yes DP👍Simply put a plumb mark of the existing pitch onto a piece of 6x2 and mark your birdsmouth in the usual way). Then go your existing rafters and get the height above plate measurement. (effectively finding your existing birdsmouth). Now measure down the plumb line on your 6x2, the HAP measurement from your existing rafter, and difference between the two will be how much lower the new plate will be👊Hope that makes sense🤔Cheers Del
@@thetallcarpenter Top banana, cheers Del
I would have went the full 390 the first time and had some firewood to take home.
I like your style Stevie 🔥 😎
Have you got a video on how to work out rafter angles on lay boards
Your plumb cut at the top is the degree of the roof you are pitching, The foot cut of a rafter on a layboard is a seat cut of the roof you are pitching with a compound cut of the roof the layboard is on, mark the angle of the seat cut on the side of the rafter then flip your circular saw to the degree of the roof you are pitching on to and cut along that line. Simples.
This might help also.
ua-cam.com/video/PmD8ViTt8NQ/v-deo.html
Yes I have Richard👍It's the most viewed video on my channel👊 Search, cutting lay boards and jack rafters' 👍Cheers Del. (and Robs reply to your question is also SPOT ON)
I couldn't of explained that any better myself Rob🤩Cheers bud
@@thetallcarpenter Happy to help dispel the mysteries of layboard jacks!
Hi Del, is there an easy way to work out rafters where the wall has two different cavity depths?
Hi Dan🖐If you want the soffit and fascia to match, then you must calculate your rafter length by measuring from outer brick/block skin to outer skin👍 Once you know your rafter length, you can use the lower plumb mark, (this would normally be your height above plate and the verticle/plumb part of your birdsmouth), and then plot back up the rafter your cavity width giving the the true 'outside of plate' mark. From here you can set your birdsmouths. Remember that the birdsmouth on the side with the wider cavity will not be as deep as the one on the side with the smaller cavity👊 You can just add on past the lower plumb mark how much you want for your soffit overhang 😎Hooe that makes sense🤞Cheers Del
Del, thanks that does make sense. The change of cavity is in the same run of wall so a bit awkward, but I always try to work off HAP. Just didn’t know if there was an easy way to work this out like you demonstrated the different wall plate heights.
@Dan H There may well be a quick and easy way Dan🤔but I can't think of one yet, and I've not seen anyone else do it. Maybe someone will read these comments and enlighten us both🤞
👍🇮🇪☘️🤗
Cheers John😎
How do you figure out when your rafters sit ontop of your ridge? With that notch out? As apose to usually butting into the side and flush with the top. Cheers.
Hi Christopher🖐It's super simple. When setting for your rafter length, DON'T subtract the ridge thickness from the overall span, this will then leave the rafters to but together at the top. Then just mark out the birdsmouth at the heel of the plumb cut to suit whatever you want them to sit on, be it timber or a plate on a steel👍Cheers Del
@@thetallcarpenter ahhh so don't subtract ridge thickness then from that plumb cut go down 2/3 same as birds mouth?
@@christophercrowle9753 BOOM👊
@@thetallcarpenter thanks very much all the best great content.
@@christophercrowle9753 Cheers bud👍
How do you calculate the ridge position cos if you have different plate heights and pitch is equal the ridge won’t be central
Hi Ron🖐The ridge positions itself when the rafters go to it👍What I did in this instance is cut both my rafters, held them in position, put a screw in through top to temp fix them, and then attach a prop down to the floor to hold them up. Then I slid the double 'ridge' beams in, propped them up and cut the rest of the roof. The brickies then built the ridge in as they finished the cable and the other end into the original roof, and then had a 4x4 king post under it down onto the steel beam below👊Cheers Del
@@thetallcarpenter thanks for that, I’ve never used a roof calculator didn’t have them in my day, cheers 👍
@Ron Bowen To be honest Ron, I never used a special roof calculator for years either, as its only right angle triangles which are simple to work out👍
@@ronbowen9250check out my comment on this post for an explaining on how you would find the ridge position prior to pitching. You simply need the individual run of either the longer or the shorter rafter and measuring that off the pitching line then plumbing up shall give you a rafter accurate ridge position.
Hi del, what if the measurement is greater than the depth of your plumb line,
Hi Stephen🖐I would simply tack an extra peice of timber on the underside of the rafter and run the plumb line onto it and then mark it at the correct drop👍Thanks for your comment 😎 Cheers Del
Hi del
If the difference was say 180mm and you were using 6x2 timbers would it work if you measured 90mm down the plumb line then marked across with your seat cut line then mark another plumb line and measure the other 90mm then finally Mark another seat cut line
I haven't tried this myself but I was thinking if this worked it would save tacking a bit of timber on
Just like to say it was a great explanation on your video 👍
@@ilijadjujic5911 Sorry bud, I cant quite get what you're saying into my head, but I think what you've suggested is correct🤔🤞Cheers
@@thetallcarpenter when I get a chance I'll give my suggestion a go then try it by tracking some timber as you suggested and report back
Ever concidered a carpentry novel Dell?
It would take too long bud, as I only write in CAPITOLS🤪Cheers Del
What app is it you use ?
Thanks.
Hi Sam🖐hope you are well bud🤞I actually have a list of the multiplication for pitches from 10° to 50° degrees printed on a piece of paper that Dan Cox gave me👊It's that or his app at Essential Carpenter Tools. Failing that any right angle triangle calculator on line will do the same thing👌Cheers Del
@@thetallcarpenter You can work out the run per metre for any pitch roof by using the equation:
1/Cos x Pitch in degrees. example: 35 degree pitch roof. On a calculator press 1, divide sign, 35, Cos button, then equals button. that'll give you 1.221 which is the run per metre. (times this by your clear run for true rafter length)
For Rise it is Pitch Tan x Run. (Run being 1 will give rise per 1m of run)
Lol, oh it just dawned on me lol,, 😅
I'm wishing I would have taken more time with this video and explained this kind of thing, but I'm always in a rush😲
So does that mean the edge isn't in the centre of the building then?
Hi there🖐If you mean the ridge, then yes, it will not be in the center of the building👍Cheers Del
Yes sorry I meant the ridge. Thanks for the reply Del. I’ve never come across this before but this seems like a great way to over come the issue. I’ll keep this tip in the arsenal. 👍 great video
Up an till today this is how I worked out using formula shown in this video....
ua-cam.com/video/IA-riDdC3Ak/v-deo.html
Hi Adam🖐I've just skipped through that video, and it's a bit more long winded than how I do it. However, essentially my method will give you the difference in the 'run' measurement by just adding or subtracting from the plate to plate measurement, the distance of the level/seat mark I made between my dropped 195mm mark and the top of the new plumb cut at the upper rafter edge👍(don't know if that's last bit makes sense🤯). Cheers Del
@The Tall Carpenter yeah totally get what your saying. As I said until I see your video that how I used to do it short of hold a pair of rafter up at the right degrees. Your method is alot easier. I feel the method in the video I linked still useful in situation where there is a massive difference in plate heights? I've had it where there's been 1500 - 2m difference in height. Would you still do it the same way by adding timber to bottom of rafter to get you line struck? TIA
@Adam Padmore If the plates were 2m different, then I would do it even simpler🤔 I would just get an online right angle triangle calculator and put in the pitch and half the drop/rise, (opposite), which would give the rafter measurement,(hypotenuse), then I would just add/subtract this from the original, equal height rafter measurement as per the video👊Really easy🤩 (you do need Internet service though😉)
@@thetallcarpenter ah never thought of doing it like that will bear that in mind thanks!
I second Randy , click like then watch even though you might as well be talking Chinese 🤔😵💫🫠😆😆🧱👍🏽
I appreciate your comment Steve🤗Enjoy the rest of your weekend bud👍Cheers
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Cheers Richard🤩