Blind Valley Jacks

summertime

could anyone tell me how to work out the angle of the side cuts to the valley jacks on a blind valley, I have allways scribed them on a piece of scrap with a plumb and foot cut on it, there must be a better way, good at trig and maths, I live in Manchester UK

Grumpy

Yeah ummmm welcome to the site. I'm moving this thread because it has nothing to do with introductions.

Double-A

Blind Valley Jacks... Didn't he play with the Yardbirds back in the '70's'?

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K2

Yea welcome. I'm thinking a blind valley is what I might call an overbuild with no actual valley rafter?? Probably need to get the terms down because I think youse guys in the UK have a funny interpretation of the English Language. And maybe I might call the cuts you are looking for the bevel??? Ther'll be some guys along that are more up on framing than me and better at the English language. But welcome again.

joasis

Around here a blind valley is running into a straight roof line on an intersect, building up, or running the valley from the existing roof deck....the cuts are really simple, since the roof pitch is the only angle, the rafter end is the reverse of that angle. No math needed.

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Joe Carola

We call them false/blind valleys, if that's what you’re talking about. A valley lays flat on top of another roof.

If the pitch of the new roof is 8/12, I mark the 8 for the plumbcut and the 12 for the level cut and cut that out of a piece of rafter scrap and use that as the pattern. It's the most accurate and fastest thing I've ever used.

You just need to know the pitch of the roof it sits on. If the roof is an 8/12 like the new one, then when you make the cheek cut bevel for the level cut that sits on the valley by setting set your saw to 33.69º or 36.5 – 37°.

If the roof sits on is a 12/12, then you set the bevel cut for 45°.

I hope this is what you’re looking for. I’ve attached a drawing with 1-2-3 on it. Can you tell me which angle you’re talking about?

Attached Thumbnails

 

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Joe Carola

maj

I use a framing square with stair gauges when cutting rafters (common or jack). One gauge is at 12" on the blade, the other at the corresponding rise on the tongue. ie. 8/12 pitch.... one gauge at 12", the other at 8" on the tongue. The 8" side (tongue) is your plumb cut, thew 12" side (blade) is level cut. The bevel would be the corresponding angle of the roof pitch for which the rafter is sitting on.

True valley framing is a bit more complex, but similar numbers game.

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summertime

Many thanks to all who answered my query, Hi to Joe Carola , the angle is nummber 1. I am an allround carpenter who deals with everything from fitted furniture to formwork so you see roofs come up about once a year. great forum, will send picture of the job as it goes on if it is of any interest to anyone, thanks again

maj

We love pictures.

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Bradracer18

I'd think.....and I don't know for sure, so Joe please correct me....but for angle number one.....you must first draw the pitch of the roof its running into(the roof on the left)......and then also set your saw to that pitch(but in degrees)......

maj

Yeah Brad, that's the bevel cut we're talking about.

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Bradracer18

....so then what is complicated about it........or in otherwords, what is still not understood?

maj

Did I miss something?
Who's not understanding?

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Bradracer18

ok........guess I thought he still didn't understand......must have missed the post, sorry

Joe Carola

You don't have to draw the pitch. You just check the pitch on the existing roof however you normally would do it. Look on your speedsquare, Construction Master Calculator or whatever way you figure it for the angle of that pitch and then set your saw tilt to that angle.

Also, for the ridge cut that sits on the existing roof, the angle for that is easy too. If the existing roof for example is an 8/12 pitch all you need to do is hold your square 8 on one side and 12 on the other side at the top of the ridge for example in this same draw, the 8 would be on the ridge side and the 12 on the left side.

Just scribe the 12 side and that’s the angle that sits on the roof.

Attached Thumbnails

 

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Joe Carola

summertime

Thanks for your help, halfway through job in picture, did footcut on jacks with handsaw, rest with mag 77

Attached Thumbnails

 

Joe Carola

What do you mean "Footcut" with handsaw?

Is that the level cut on the bottom of the jack that's sirs on the blind valley?

What angle did you have to cut that you needed a handsaw?

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Joe Carola

Bradracer18

First let me say.....looks like a mess of roofs. Next.....I'm with Joe....why the handsaw. Should just be able to cut normally, with a bevel(certain degrees) set on your saw.

summertime

Hi joe and all, I am over 60 and was brought up on hand tools, the axe and cut wooden plugs etc, I have never used a chop saw to do a compound miter cut, allways sawn em by hand, but trying to teach my boy its the power tool age, but its hard to teach an old dog new tricks,
only do a roof every now and then, so fall back on what I am used to
going to have a practice at home

Joe Carola

If your talking about the level cut at the bottom that sits on the blind valley and the angle going up the roof, then just set the circular saw you have sitting there in the picture to the angle of the roof it's sitting and run the saw down the level scribed line.

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Joe Carola