if u have the rise of an arch and the span can u get the radius
tscarborough
jshuatree
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the formula in this business is production, period... I'm a layout guy, i run everything to grade flash,weep, hang the lines, 3 courses,mark the heights/poles and I'm on the next one....the bombers follow me they don't have to think about **** just lay brick...it works and i work with some talented guys if u sneeze they got 50 on u and you can sell it.
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Why wouldn't what?
code is code--nothing to do reality. What Bytor is talking about are the millions of jack arches that were (are) built before "code" or even steel that hold up well for centuries. As long as there is no spreading of the wall (caused generally by faulty foundation movement) a properly constructed jack arch will hold up just fine. Admittedly, a bit of radius does make for a stronger arch.
JVC
JVC
add steel man, you need steel under a jack arch.. it's flat .not only that it should be flashed properly as part of a drainage system in a cavity wall including weep holes.
yeah your right but they were not jack arches holding up for centuries,, jacks are flat, they can't take the load like the historic arches your refering to... none of them are flat..they all are gothic, tudor, etc, the aqua ducts are still standing anything with a curvature will last . walls built today around the average home are cavity walls intended to drain water..where does your solution fit in, no flashing, no weeps, no nothing!!bound to fail...
I know what a jack arch is--have built hundreds of them during a 35 year career. (with steel btw) Just saying that the steel is a convenience, and a proper jack (not talking a course of soldiered bricks or stone) can withstand the load without it. Can show you plenty of jacks around here that are 100-150 years old and doing just fine--of course they are over openings in real masonry walls,--not 4" veneer.
JVC
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6,626 Posts
You have the formula up there, of course you can calculate it. Personally, I do not like iron in arches, and iron does not last nearly as long as masonry. Most of the issues I see with windows have to do with the steel rusting, expanding, and popping the joints (usually brought on by poor flashing, admittedly).
The amount of masonry that an arch has to support is also calculable , and it is not a very high number in relation to the opening width. Jack arches do not need iron, and if yours do then they are decorative arches not a structural jack arch.
The amount of masonry that an arch has to support is also calculable , and it is not a very high number in relation to the opening width. Jack arches do not need iron, and if yours do then they are decorative arches not a structural jack arch.
Although a Jack arch is flat, it is set out on the radius of a segmental arch, and all the joints radiate to a single striking point, so it is really a segmental with the ends extended top and bottom to form the flats. Ideally it should be built with gauged or rubbed brickwork with joints no more than 1/8 inch thick. Done properly it will easily bridge a 4 ft opening and there are many examples here a few hundred years old still in good nick.
I was being a stubborn, argumentative, jackass last night/this morning. Sometimes I can’t see past the end of my nose, I was rereading my posts and I can’t believe I was even arguing the point..Way to much Jamison, no excuse for my behavior. I've been shut down since we got pounded with snow here, my wife is ready to shoot me in the face, from the same sort of stubbornest I displayed here. Can’t learn **** if the ports are not open, and I have a lot to learn.
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Don't beat yourself up about it ,we are all here to learn and contribute where possible .These are some of the finest masons & tradesmen around and it can be a humbling experience. & The winter can get anyone depressed, however its only 4 wks till spring.
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321 Posts
ditto....no iron needed in a properly constucted jack arch
and yes there is a formula....l have one formula thats 2 pages long and will give the dimensions of every cut and voussiors in a arch..
l should aslo clarify that l would use a angle iron on a jack arch just for the added security given that most would be on wooden framed houses and could experience frezze thaw cycles and some shifting...for me it would just be added security and in the end cant find fault with folks doing that
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2,877 Posts
To get back to the initial question, my formula is r=1/2span(squared) +ht(squared) over 2ht.....I don't know how to type this out as Bytor did....but this is a formula I use all the time in segmental arches......trial and error is for guys that don't get geometry....
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321 Posts
this is generaly what l do,,lm more hands on than a pencil pusher as theres real world varibles that dont work well with formulas sometimes,,,basicly build your form and layout and git at it
Crosby...."it works and i work with some talented guys if u sneeze they got 50 on u and you"
thats the diffrence between a journeyman and a shoemaker
this brings up another qu like over garage doors you see alot of cracking whatis the best way to prevent this
i always will lag my iron into the header when going over garage doors.this helps to keep the iron from moving.also a 6-8 inch lap over the brick is what i call for.i will also use jack legs under the iron until the wall has had a chance to set up.generally about 3-4 days.
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