Building an Extension #7 - Roof Build-up & 3 4 5 Rule

In Part 7 Roger talks about the preparation for the roof. Amongst other things, the 3 4 5 rule explained.
The Extension project is now up to plate level so it’s time for Pythagoras’ theorem.
“Plate level is the timber plate which is going to hold the roof structure including the roof joists, hips and roof rafters.
“When you put this on you need to spend a lot of time getting this right because carpenters curse bricklayers like mad if they’ve bedded the plate on and it’s wrong and some carpenters even prefer to put the plate on themselves.
“Luckily Mark, our bricklayer, is very diligent and he bedded it the old fashioned way. It comes off the existing plate of the house and we used a laser level to ensure that it is level all the way round and we’ve also checked that the whole thing is square which is also really important.”
3-4-5- method
“You can do that using a folding square but an alternative way to check the plates are square which can be useful on larger roofs is to use the 3-4-5 method.
“Take any 3 measurement such as 30 inches from the corner down one side, then measure 40 inches down the other sid
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[@adrianhill9208]

Love these videos. A refreshing change from the deluge of American videos. Keep em coming

[@CA-sj6oo]

You sound like an Anti American A$$hole!!!

[@benh1216]

@@CA-sj6oo I wouldn't say anti American. Maybe what they mean is it's nice to see some British building videos? I mean there is nothing wrong with American building videos don't get me wrong but YT channels like Skill Builder and Stu Crompton are my 'bread n butter' when it comes to construction videos!

[@righteouswarrior7621]

Trust💯 God sent😉

[@stan4474]

Love your videos Roger , I learn all the time from them.

[@chrisainsworth2616]

I've been watching your channel for the last few months, I've learned alot through your knowledge, but your passion and inspiration is what really makes a difference. I'm just about to retire after 24 years Army service and am doing some very basic work on my house and it's helped alot. Thanks.

[@sprintervanconversions]

Your practical knowledge is never ending Roger!

[@dominikjesiolowski5760]

Such talent, hard to believe this is not scripted and rehearsed many times. Not one unnecessary word, during lockdown and schooling from home you should be a teacher Sir!

[@liambrown5375]

I luv an old school builder. Keep up the great work

[@Shakeel_._Ahmed]

3-4-5 Bravo! You can't believe how helpful i'm finding these videos! Thank you for your efforts.

[@ceesaydesignsolutions]

3-4-5, right angle triangle, Pythagoras' Theorem! I have something to teach my students in my Mechanical Principles Class Now!

[@nayheem]

Great video I like the way you explain construction methods. More like this needed - learnt something new.

[@jeffbradley8783]

I always look forward to the next episode RB, very entertaining and informative at the same time.

[@SkillBuilder]

Glad you enjoy it!

[@jeffbradley8783]

@@SkillBuilder you boys must be so busy, working and producing all this great content. 👌

[@alejvalencia1553]

3-4-5, amazing! Really enjoying this series.

[@johnlsullivan5180]

I'm in the trade and really appreciate the videos ,interesting to see other jobs.

[@callmedee123]

Hello from California! I learned something... Great content, keep up the fantastic work.

[@malipat5809]

Learn so much from Roger- cheers buddy

[@4D1989]

More of this please! Mainly American videos on framing and roofing. Great to see some English videos 👌🏼

[@cedarridgen2791]

Nice videos. I'm Tenneesse U.S. I just found your channel and I love it. I'm not a house builder but i familiar with U.S. construction. I didn't know in Britian you use brick walls as load bearing support walls. Houses here in the southern U.S. the brick is laid last, after windows doors, eaves soffit and fascia. It is strictly a veneer. You guys are great craftsman! Fun to watch.

[@SkillBuilder]

Welcome aboard! Nice to have another American viewer, there are lots of differences in the way our two countries build and it is interesting to know them.

[@peterbell4154]

Roger, me as a long time Carpenter and Joiner I have learned to Curse the bricklayer quietly as more often than not they are bigger than myself so i just have learned to get over what is thrown at me.

[@SkillBuilder]

That is a great comment.

[@MrJFoster1984]

Hi mate. Been in contact with Anthony at the Brick Brace company after seeing your other video putting the steels in. Very handy for us always changing corroded lintels and beams. Liked all your videos so far, have toyed with the idea of doing my own, just haven't found the time. I think people like your videos because you clearly explain what it is you are doing and connect with the viewers. Keep it up mate. Jerry

[@SkillBuilder]

I am glad you contacted Andy, he is one passionate guy. They are handy to have for all kinds of jobs. I reckon scaffolding companies could use them. As for making videos, it does take a lot of time not to mention the kit we keep buying.

[@tigertruckerman]

Helicrete Sydney he is great teacher, no 2 ways about that

[@roberthigbee3260]

3 4 5 right triangles rule!! I knew before about this particular "right" (90°) triangle where the legs are 3 & 4 and the hypotenuse (the long side) is 5, but I never knew that carpenters could use this trick to check if a corner was 90°. Pretty cool! Permit me to put in my own 2 cents: when you use the 3 4 5 method to check squareness, you will need to mark your end points very precisely since if you are predicting where, for example, a 9.144 meter run (30 feet) ends up, even if your 90° corner is off by only a quarter of a degree (0.25°), the other end of the 9.144 meter run will be off by 39.9 mm (1.57 inches).

[@SkillBuilder]

Robert You are so right, that marking is very important. If we have two corners we square both and run a string line between them. You can see if they are within your tollerances

[@markmackie100]

Gret Roger. Always like you r videos mate. Funny though how you bamboozled us with the maths and tables, and then said, just put a piece of timber on the drop and mark it. LOl

[@thomo74]

Bloody good videos ! I’m learning so much! Thanks!

[@billywhizz98]

Top quality workmanship

[@nickwatson2213]

three, four, five. i love it, i've learn't something new and really useful.

[@Carl-yu6uw]

great info cheers - most thorough explanation of wall plate and ridge detail.

[@bloggs692413]

Great explanation of whats involved

[@andybtec]

First time I've heard of 3 4 5 . Something I will use again and again

[@smurfman691]

Basically applying Pythagoras formula

[@SkillBuilder]

smurfman691 Yes every time I use that I send him a quid

[@SkillBuilder]

andybtec That is great, I love it when you get a little trick you can use. When I get a chance I will show you a few other measuring tricks that you can tuck away in the back of your mind.

[@4D1989]

Learnt that at college! Tried and tested 👍🏼

[@girlsdrinkfeck]

additional calculus ratio mark

[@krugby8836]

So useful, learn plenty.. 3.4.5 fantastic thanks

[@pawelbroniewski7100]

Nice. Another score for Roger 🤗

[@roberthigbee3260]

If you like old time wisdom, here's how you can check the levelness of your project using a method that the builders of the Egyptian pyramid used - The Egyptians dug a trench the whole way around and also into the the pyramid foundation site and filled it with water which created a level reference. I know you don't want to dig a trench, so, first you get yourself a long garden hose and then stick two ~12" long clear plastic tubes on the ends of the hose (water tight) and then add black circumferential lines around the tubes at their centers. Next, you securely affix one end of the garden hose at one location on your build with the black line aligned to, for example, the top of a beam. Next, you affix the other end at any other spot with that end's black mark at, for example, the top of another beam. Then, you fill the garden hose with water (use a funnel) until the water is up to the mark on the first reference end (make sure the middle of the water's meniscus is at the mark, not the outer edges). Now, if you go over to the other end, you can tell how far off level that other location is by measuring the distance from the water level at that end to the black mark on that end. This trick works no mater how higgledy piggledy the center of hose is, as long as there is water in the whole hose and as long as the center bits of the hose are below either end and as long as you are not off-level by more than half a foot. You can check the level over as big a site as you want as long as your garden hose is long enough.

[@bobhatcher5505]

Great stuff as always Roger! Thanks.

[@rex182k4]

3 - 4 - 5 otherwise known as Pythagoras' theorem

[@psymon25]

fantastic explanations again love these videos

[@mrcaboosevg6089]

"You can't expect these buildings to be spot on" Describes every single house i have ever been in, even newer ones.

[@chippyminton8711]

In an ideal world everything would be millimetre perfect, level plumb and square but the reality is it isn't. After 35 years of site work it's a welcome surprise if a building is within half a brick of level , square and plumb and i'm not joking about that.

[@billvekas3465]

Your job is great. You love the winter weather but i hate it. It freezes my fingers and i can't press the button's of my total station. I used many kinds of glove's but still i can't find a suitable pair for me until now. I can't write down wearing gloves or even to open a blue print just for reference. And i can't even think about windy days.

[@danwoodgate_bxng]

Where do you supply your timber from? it seems to be really nice quality, great vids, thank you

[@elimarr17]

how long did the extension take to complete? great videos by the way.

[@tombrehony6277]

Allways bed the wall plate , that's what ensures the load is evenly spread across the plate...

[@peterbell4154]

Roger, Could I just say you don't have to look up the internet or use a table if you have the calculator that you may use to multiply, you need not do that if you are using an ordinary calculator that has the button that shows COS: short for cosine Just take the run that you spoke about say for example, punch in 2.4 for the run Then hit the divide button then Cos button then punch in 35 =2.9298 length of rafter, so shortened version looks like this 2.4 divide COS 35 degree = rafter length it probably reads more complicated than it really is (HONEST)

[@SkillBuilder]

Great tip. We will try it on the next video.

[@peterbell4154]

@@SkillBuilder Really appreciate your reply, makes me feel a bit humble that you will try this tip. Thanks very much. I promise you it works, let me know how it goes.

[@robertoterella9864]

Roger the pice of timber over the last row of bricks is there any waterproof on the bottom of the timber ? I am not sure if this pice get wet.. Maybe it pulls out some water of the bricks ? Sorry for my English

[@SkillBuilder]

We call that the wall plate and it sits on top of the inner skin of brickwork. The brickwork is protected from damp by the roof and the cavity so it should never get wet. If the brick were just a single skin it would possibly benefit from some damp proof membrane on the underside but that would be an unusual construction.

[@robertoterella9864]

@@SkillBuilder ahaaa you guys are building always with two parallel brick walls. We build with on stone that has a thickness about 36cm in addition a insulation of EPS round about 14cm on the outside witch helps to keep the entire brick longer warm in the winter. well other countries other philosophies

[@ratchriat1716]

found this video very informative thanks .

[@TheAsa1972]

Easy way is get up to wall plate height and get a truss company in to do that ,Works out cheaper then getting a couple of Joiners in to do the roof

[@gdfggggg]

I’m a trial and error kind of guy, done lots of roofs and now I’m at the point where I can build a roof to a good standard. I’m doing a loft conversion (on a 30’s semi) at the mo and I’m fitting a new roof onto an old wall plate (from hip to gable) that is 60mm out of level and have to match the old tiles and fascia board (next door) into the new. Your method won’t work, as to match the new roof into the old and keep the eves (looking) straight at upper 1st floor window height I have no choice but to cut the roof pissed. Each rafter has to be cut individually. The new ridge is nice and level as is the new loft floor but the fascia board is pissed and the rafters have to be cut to suit. The tiles next next door are also 100mm out of line from fascia to ridge and the outer left hand wall has a 50mm bow in it....sleepless nights for me 😂 I’ll get there. Sorry to bang on, just needed a shoulder to cry on 😁. Good work though.

[@rhysevans7903]

Still probably better built than a new build estate

[@MatthewDunniscool]

Fascinating

[@TheAudiostud]

"Great work Well done"

[@MrJFoster1984]

Don't forget the wall restraint straps Roger :-)

[@SkillBuilder]

Helicrete Sydney Highlighted comment Thanks,it is easy to forget these things but they are in, all tied up and buttoned down

[@eddieharding5961]

The old rafter would be 4" and the new ones 6" so the wallplate on the new bit must be lower .

[@tigertruckerman]

What are those plates sat on , are they on mortar or straight on the blocks , couldnt quite see

[@SkillBuilder]

The plates are bedded on mortar to get them absoloutely level. Then I spiked them through with helical fixings that wind into the block. Then straps to hold them down in hurricanes. That roof is going nowhere.

[@ashrafhelu4664]

Thanks many Roger

[@dangiles5038]

I prefer to go for the diagonal measurements for checking square on plates, more accurate over a larger distance.

[@SkillBuilder]

We did that too and should have said so.

[@joeframer9642]

Just measure the rise ( top of ridge) and use your run ...a construction calculator will give you the pitch (degree) and diagonal ( rafter length) minus half the ridge thickness.....push the button again for hip or valley rafter. Always match ( dead heights) distance from top of plate to top of rafter , plumb with the outside of the plate. .....of course there’s much more ...like “drops” which is the bottom of soffit to the top of the plate to match up trim....and so on....

[@asef698]

Joe Framer i think he knows what he's doing. Everyone has there preferred way

[@SkillBuilder]

Thanks Joe. That would have helped and I might even have that calculator lying around but I was trying to run the rear rafter in and match the height above plate so the roof ran through to the existing roof. It is surprising what a difference one degree makes.

[@joeframer9642]

ashley sefton well I was trying to help since I own a construction company,building custom waterfront homes for 30yrs , still going strong. ..I believe he said he’s a plumber and the got the angle wrong the first time....using this method gives you the exact degree without error when remodeling like they are doing. .but thank you for your concern.

[@MrJFoster1984]

Joe Farmer. You can always set up a string line to work out your plumb cuts. Birds mouth is always 90 degrees to plumb cut. I would always hold the rafter in position on a small job like this and scribe/trace the PC with a level at the ridge and the same for the birdsmouth/seat cut. If you want to be fancy you can use half your roof width and with the old A2 + B2 = C2. Hip roof just uses a common rafter to determine the length of the ridge and so on. You can't always use a roofing reckoner if you are working to something out of square or level when matching new to old.

[@joeframer9642]

Helicrete Sydney it’s all math , no string is needed or placing a board up to scribe...it’s basic math, rise and run..use a construction calculator if you want to...

[@stephengreenwood11]

Are those radio ear defenders Robin wears?

[@SkillBuilder]

Yes he wears them all day long. He is tuned in to alien spacecraft, which he swears are watching us. Sometimes we catch him talking to them in strange tongues.

[@johndaniells4440]

How's robin's new gaff coming along?

[@SkillBuilder]

We need to get back down there. He is moving ahead and we are only catching bits

[@davidpalmer3040]

John Daniells ‘

[@Truevisionsolutions]

Is Jimmy Bullard a builder now!

[@noelter]

Explain down to a Tee. 🤔 Tea break.

[@millwalltopboys]

get a better tape mate that floppy things as good as my old bill

[@owenmills1596]

Who ever told you that u will never need pythagoras Thereom lied.

[@SkillBuilder]

Very few builders and carpenters know the Pythagoras Theorem. They rely on tables and apps to arrive at the measurements. Even if you do know it you still need to work the square root of the hypotenuse out to get you back to a usable measurement so you might as well let your phone do the whole thing.