cut rafter roofs

[gangman]

The easiest way to understand this is to draw it.

Use a protractor and draw a 40 degree angle then draw a perpendicular line at a right angle to the horizontal line. The resulting angle at the top will be 50 degrees.

The pitch of a roof is the angle between the slope of the roof and the horizontal, ie the angle at the wall plate not at the ridge.


If you still aren't convinced, buy a ready reckoner.

Roof pitch 40 degrees, common rafter - seat = 40 - ridge = 50

If you're building a new roof you can't really go wrong using the reckoner. All the angles are there, as are the rafter lengths.

 

[justlead1]

Hi It is normally the ridge height that causes problems with planning, so i would suggest before you start cutting at 40 degrees. Put three pins in the lawn or drive and connect with a string line and mimic measurement of height in relation to wall plates. This should give you the confidence with common rafters, ridge board etc.

 

[noseall]

The easiest way to understand this is to draw it.

Use a protractor and draw a 40 degree angle then draw a perpendicular line at a right angle to the horizontal line. The resulting angle at the top will be 50 degrees.

The pitch of a roof is the angle between the slope of the roof and the horizontal, ie the angle at the wall plate not at the ridge.


If you still aren't convinced, buy a ready reckoner.

Roof pitch 40 degrees, common rafter - seat = 40 - ridge = 50

If you're building a new roof you can't really go wrong using the reckoner. All the angles are there, as are the rafter lengths.

you seem to do things backwards to me gangman?

on a 40 degree roof my ridge plumb cut will be 40 degrees and this is how i set it on my saw.

i have never needed to use the 50 degree thing at all.

ever.

 

[gangman]

Noseall
Next time you are around your local town, check the book shops for the Roofing Ready Reckoner by Ralph Goss. A brilliant little book, costs about £14. I've just bought a new one, it was a case of lending my old one out and not remembering who it was.

When you look at the tables you see the way I do it. On a 40 degree roof the ridge is 50 degrees. Also for a hip roof it gives you a ridge and seat angle for the hip and also the top cut for the jacks.

It too me less than 30secs. to find out that on a 40 degee roof the hip plumb is 59.5 and the seat is 30.5 and the top cut on the jacks is 37.5. No calculating, no trial and error, so much easier.

If you've not used this book Nose, trust me, have a look mate. It's like a mobile, once you've got one you don't want to do without it.

 

[noseall]

If you've not used this book Nose, trust me, have a look mate. It's like a mobile, once you've got one you don't want to do without it.

i trust you gang, and if i get the chance, the book will be in my works 'man bag'.

 

[alan49]

gangman your very right in what you say books brill ,but i thought i was marshall goss he is the roof cutter master have his books but all in foot runs ,him being a yank

 

[AtoZ]

it is possible to set a bevel gauge to 40 degrees, place it on a rafter and have it read 50 degrees. it depends where you place the bevel.

i place it along the length/side of the rafter but a friend placed it on the end/cut of the rafter. thats how i know this is possible.

the plumb is cut at the ridge. that cut will be at 40 degrees.

my apprentice is taught the same way at college; as the way i do it.

it may well be possible to do it another way but that does not make it more 'correct'.

as for that .5 hip cuts.
roofs are cut in rise and run and they are mostly worked out in inches.
i should like to see someone cut a .5 angle on a hip or rafter. it wont happen.

i'll stick to my way of doing it as i can read it from my framing square and dont need a book from someone ive never heard of to tell me different.

why complicate things! particlarly as most times a chop saw will be used and most c/saws wont cut 50o cuts.

each to their own i suppose.