Dan Cox Answers Your Roof Construction Questions

Dan Cox answers some of the many questions posted in the comments section.
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[@thetallcarpenter]

Dans huge experience of roofing is clearly evident as he casually and comprehensively answers the questions put to him😎Really glad we are seeing more and more of him on Skill Builder👌Cheers guys.

[@Ultimate-roofing-square.]

Thanks Del, much appreciated. 🙌

[@terrym2482]

G'day dan how much for the hinge jig to Victoria preston 3072

[@terrym2482]

Australia

[@SteveAndAlexBuild]

Dan the man ! Great to see more of him sharing his vast knowledge 🤜🏻🤛🏻🧱👍🏼

[@Ultimate-roofing-square.]

🙌🏻. Thanks chaps. 👊🏻

[@garulusglandarius6126]

Wow, Dan doesn’t even realise he’s a genius, love this guy and his work is second to none 👍

[@edthompson9337]

If you have ever stripped off an old pitched roof you will quickly see the reason why the timber is fixed bow up, the timbers will always dip over time, quite considerably on some.

[@robertjones3694]

been using dans square now about 4years can not fault it brillint

[@peefor135]

Always great stuff from you pair. Love the old metric imperial/measurements.. 1inch over 5 metres.

[@kiwigrunt330]

I prefer metric jellybeans over imperial cauliflowers. Don't understand why everyone doesn't use that...

[@stephenmccoy898]

I bought dans square, ive been doing roofs for long time, the square is just brilliant and the app, never fails, great job and i recommend any roofing joiners to grab 1 they really are tbe the dogs

[@Ultimate-roofing-square.]

Thanks Stephen. 🙌

[@cliffcarlo180]

If I had to choose between an armchair warrior and Dan Cox to build my roof, I know which one I'm choosing. Dan Cox 👍👍👍👍

[@Ultimate-roofing-square.]

Thanks Cliff.

[@DouglasCarnall]

Appreciated the bow up/bow down discussion. Bow down might close up attached slates, but a rafter's primary function is structural so I agree with Dan

[@kiwigrunt330]

I doubt you would be able to see the difference in the length of a slate.

[@paulhiggins9492]

Bow up Dan , joiner here for 50 yrs…. Who are these people.

[@johncrannastructuralengine8177]

from a structural engineer I would say bow up as any load will make the rafter deflect down (and not up!!) but also in all deflections of the allowable deflection that engineers do there is an amount of creep that has to be added into the instantaneous deflection from the load applied. That is (the creep) that over time there will be an added deflection due to the nature of timber coming from a living source!

[@sparkyobrian6417]

I bought the imperial version and its the bees knees, great tool, nice and solid.

[@mrsbradpittiful]

Crown up

[@LeeTillbury]

Good work fellas👍🏻

[@thesmallnotesduo]

Awesome skill and knowledge

[@DuncanEdwards.]

I live in the UK and prefer Imperial measurements

[@I-am-not-a-number]

Reference; The Carpenters Metric Roofing Ready Reckoner by W.E. Gray. A simple little blue book with all the tables and diminishes.

[@gbwildlifeuk8269]

* dimensions!

[@I-am-not-a-number]

@@gbwildlifeuk8269 The diminish, in roofing terms, is the difference in the lengths of the jacks in terms of spacing and centres. Example, at 35 degrees with 450 mm centres each jack will decrease 549 mm from the common.

[@BillyMustang101]

​@@I-am-not-a-number can work your diminish out on a calculator as well

[@trevormorgan6611]

I would not recommend marking your plumb cuts with a bevel as shown. Any dip or camber in the top of the rafter will be reflected in your plumb cut! Use a string line just clear of the tops of the rafters, and plumb down with a level. Nice to see that you have altered the design of the locking knobs on the square too. I bought one of your earlier ones, with the small smooth knob, and found it a pain in the butt to grip. in the cold or wet. I soon abandoned them, and replaced them with two wingnuts. It's a great tool though, and saves no end of time! No more trying to line up heavy pattern rafters.

[@kiwigrunt330]

I usually use a bubble stick to mark them. But because Dan had his string below the rafters, he is likely to have the bottom of the facia straight. The top matters less as the gutter will hide it.

[@garys628]

Go Dan......👍👍😀

[@paulcloona9331]

On long rafter lenghts bows up . Nailed to purlin generally straighten them. Dans square is brilliant. If a young carpenter left his phone at home a day with no app to look at for rafter lenght🤔 . They should be taught a few ways of doing it. One is get 2 straight rafters make a big right angle square useing 3-4-5 on the ground. At the point of 90degree's is the mark for half the span, sometimes youd have height of ridge so mark it on the vertical 90 degree timber. Get a 3rd straight rafter it will be your template rafter lay it on the made up square top of it at the ridge height mark, other end passing over the other end of the horizontal square. The birds mouth marks perfectly and ridge plum cut .also soffit heights. And can mark purlin birds mouth. This probably sound harder than im writing it😂.

[@girlsdrinkfeck]

id say bow up is better structurally , think of how wood fibres compress on eachother when bowed , like a brick bridge or arch does , under bow or flat the fibres have nothing to compress against

[@nickhaley4663]

Bow up ..... Bow down ........ I have a very old roofing text book which specifically says to fix bow down as a uniform dip in the roof is far better than any sort of bump. In fact on a cut roof with purlins it recommends fixing the purlins a half inch low and then nailing the rafters down to it. Easy enough with 4x2 but not with anything much bigger though.

[@SingleTrack66]

This drives me mad. It’s bows down on rafters, bows up on joists. It always was. I don’t know when this crazy idea of putting them bowed up came along but it’s just wrong. If you knew how to cut a roof properly (with purlins) then you’d understand why. The trouble these days is bloody structural engineers can’t calculate a roof with purlins and over specify rafter thickness and want to put steel everywhere.

[@TheBrick2]

Here is another one. Your opinion. Lean to into a tapered gap. Level wall plate and steepening pitch (as gap narrows) vs constant pitch and sloping wall plate?

[@Ultimate-roofing-square.]

Think I’d probably prefer a level wall plate, fascia and soffit and a out of level ridge. 🤔

[@TheBrick2]

@@Ultimate-roofing-square. Thanks mate, its hard to think what will look best!

[@amazing451]

Can Dan do a video on how to cut a purlin into that model please?

[@Ultimate-roofing-square.]

We can look into it Kevin.

[@willfollins9972]

Hi love your work and a top chippy. Can you please do a video on a cropped hip as theres not many out there 👍

[@nZebco]

The App has diferent maths formula than the charts Dan has. I have checked them and they provide diferent results, by some margin.

[@Ultimate-roofing-square.]

The app does take the ridge into consideration, unlike the paper chart. I’ve just randomly checked a few and it was fine.

[@nZebco]

@@Ultimate-roofing-square. Ohh I see. It makes perfect sense now, thanks for clearing that Dan.

[@Ultimate-roofing-square.]

@@nZebco no problem. 🙌

[@aliones]

my question to dan, who's no.1 in roof construction, dan or robin?

[@jamesgreen9665]

In my opinion Dan

[@Ultimate-roofing-square.]

@@jamesgreen9665 thanks. I follow a few American framers and they are definitely next level.. cutting roofs up in their workshop then fitting them.

[@oreallyoreilly6576]

Can forget oul Del boy the tall carpenter

[@Ultimate-roofing-square.]

@@oreallyoreilly6576 oh yes! He’s a great chap.

[@denty32]

@@Ultimate-roofing-square.thanks for introducing me to the Roofslayer Dan he really is on another level. Hope your well mate

[@ladytradiej8027]

You said, 'in the olden days you used to keep the ridge higher' why is that? I've never heard of bow down.

[@Ultimate-roofing-square.]

I’m not sure but many years ago we was taught it at college. Perhaps it was better for the ridge tiles.

[@villaman2261]

Be nice for some to show how to work out a cropped / Dutch roof on gable ends 👍🏻

[@covecarpentry]

bow up, 100% of the time

[@gavmorley]

Spelling whoopsie in the title 👍

[@kermitefrog64]

Put the crown or bow up for carrying weight. By the way the metric system is a lot easier once you get the hang of it because all of the measurements change based on groupings of 10. A yard is very close to a meter within 3 inches. So approximately 30 centimeters is very close to a foot. Once you see a few comparisons and start working with it going to metric is not that difficult. All automotive equipment has been using metric for decades so its not that big of a deal to switch over to what most of the world is using for measurement.

[@grantconnor2664]

Bow up and the slater should grade over it. Simple

[@gavincollins9376]

Noticed Dan hasn't a single grey hair...Good going mate..

[@Ultimate-roofing-square.]

I’ve got a few grey ones popping through if I don’t shave.. 😬

[@vintage5532]

Dan, your skills are impeccable but I need to know one thing. Can you put a Rowntree's fruit pastel in your mouth without chewing it?

[@Ultimate-roofing-square.]

No…😂.

[@vintage5532]

@@Ultimate-roofing-square. haha well we can't all be perfect I guess mate 😂

[@Ultimate-roofing-square.]

@@vintage5532 😉.

[@stephenmccoy898]

Hi dan, is the bevel you are using your own as in the roofing square

[@Ultimate-roofing-square.]

Hi Stephen, I did make it, however I’m going to get some made up soon.

[@stephenmccoy898]

Cheers, I'll have 1 when available 😉

[@danh2015]

Dan, would you usually keep your roof plane true as your square does birdsmouth from top of joist? Some joists as you know can be over 5mm bigger and I keep the inside plane true with my pattern rafter for plasterboard. Keen to buy one just need bit of advice. Thanks

[@Ultimate-roofing-square.]

Hi Dan, I always keep the top of the rafters flat for the tiles or slates. If plasterboarding underneath then you will probably need insulation, so you can batten it out accordingly. Thanks. Dan.

[@danh2015]

Thanks Dan, ordered one of your squares today. Can’t wait to try out and see how much time it saves on these 6m rafters .

[@Ultimate-roofing-square.]

Thanks @@danh2015 for ordering one. It great especially for long rafters, no more heavy patterns. 🙌

[@villaman2261]

Roof master square is far better imho , easier to use , no paper flying about in the wind ,

[@summittaedae2323]

100% put the crowns the wrong way. Gotta sacrifice the roofs structural integrity to keep the slatters happy. After all he does offer a tail light warranty 😂.

[@davewarner157]

Hi Dan Building my own garage with a tile pitched roof and I am about to fit the wall plate I have measured across from one plate to the other and the wall is 10mm in a 10m length do I have to get it bang on the same?

[@Ultimate-roofing-square.]

Hi Dave, You will lose the 10 mm.. Just cut them to the longest plate to plate measurement.

[@davewarner157]

Cheers Dan

[@TheToolnut]

I'd split the difference, subtract 5mm from the widest dimension and add 5mm to the narrower dimension.

[@bilpat5123]

@skill builder can you cut lay board angles with the ultimate roofing square?

[@SkillBuilder]

yes

[@bilpat5123]

@Skill Builder thanks skill Builder, is this included in the instructions or is there a video online?

[@girlsdrinkfeck]

bow UP 100% , think how the wood fibres act, if they are bowing up they arch like a brick bridge the fibres compress on themselves will never fail , bow down the fibres will continue to spread and split

[@patricmahony1250]

Dan were u get the bevel

[@Ultimate-roofing-square.]

I made it Patric, but hope to get a few more made up soon for sale.

[@patricmahony1250]

@@Ultimate-roofing-square. happy days great bit of kit

[@jwhite7303]

If my roofs being slated , don’t use bowed timber , simple.😂

[@MrBez007]

The hip rafter actually doesn't carry any load other than its self weight. It's a bigger section purely as the span is longer and to take the plumb cuts

[@kiwigrunt330]

Same goes for the ridge board. A ridge beam is only required if you can't stop the rafters from spreading lower down.

[@MrBez007]

@@kiwigrunt330 👍

[@plumpii7177]

Consturction.

[@SingleTrack66]

BOW DOWN ! On rafters. Up on joists. Always was. No one wants a roof with a hump in it. A bow down looks better and keeps slates tight. If you cut a roof properly and use purlins then it’s essential. Drives me mad. Look in any old text book. Ask any retired carpenter. Stop putting them up. It’s wrong.

[@LupusMechanicus]

Ya calculation app is great, you still need to know what and how you are calculating. It doesnt help you if you don't know cheif soh cah toa.