Retrofitting circular window into stone
Pascanale
| Posted in General Discussion on
Here’s a challenge to all you stone masons…I need to retrofit a conventional wooden sash circular window into an existing quarry stone veneered stud wall. The stone is approx. 3″ x 4″ by random lengths. I can cut the stones out at the mortar lines, water saw their ends to form the circle and regrout them back in. Or….what’s the alternative(s)?
Were it a square/rectangular window I’d use a diamond saw and have at it. But, you can’t cut curves with them.
Any suggestions?
Pascanale
Replies
If you want it to look like a real stone wall, you would probably cut out (at mortar joints) 8 or 10 inches extra from what you need for the window. Lay a keystoned arch big enough for the window, then cut the stone to fill in from the old mortar joints to the arch.
Your way of cutting stone out at mortar joints, then cutting it to fit the window will work well enough, as long as the stone is well supported by a stout window buck. Mortar is mud, not glue, I don't use it in tension. Stone is meant to be laid so that it would be stable without the mortar.
zak
"so it goes"
Holy Cow! I just completely overlooked the issue of weight. There's no header if I simply trim the stone in a circular fashion. A square window would at least have a embedded steel ledger. And your suggestion, albeit more elaborate, but more aesthetic, addresses this, too. Your term "window buck" is essentially what I'm calling a ledger, steel angle iron like I've used over glass block windows in cement block walls, right?
You know, I was so engrossed in cutting the stone on a curve I overlooked this weight-bearing issue. The keystone is a great idea and straightforward. The homeowner will make that decision after I tell them the cost increment. The alternative is not so simple either nor as straight forward--fabricating the buck. Could you expand on that? I'm making the window from scratch. Its mahogany with a custom profile on the interior to match the other trim--that's my specialty. This stone issue is not.
One of the great things about a stone arch is that it is self supporting, as long as the piers or capitols that form the base of the arch can not spread.
The stones refitted to the sides of the window and the other stones of the wall will provide all the lateral bearing necessary to support an arch without the need for a lintel.
You will need a form in the opening to match the curve of the window as you lay up the stones. Once you set the keystone wedge you can remove the form and install the window. When the arch is completed fill in the area above with the stones removed at the start of the job.
You can prefit all the stones to a template on the ground before you start the actual layup.
Ok, well I didn't say more about the weight because I've never worked on one of these stud wall/stone wall things. I've only done pure stone.
By window buck I mean something that would form a rough opening, so wood might be the easiest thing, but to make it curved like that while still being durable and strong makes it more tricky. This is really the perfect spot for an arch.
A curved top makes it a natural, too. The stone should form a kind of corbel arch by itself, and then you can build your arch inside of that. Without looking at it, I'm not sure about how risky it is to rip a big hole in the stone wall. I would think that if it was built well and tied to the stud wall, it should'nt move, but I'm not guarunteeing anything.zak
"so it goes"
I've looked at this problem from the builders perspective a long time and here's what I've come up with. Cut a plywood disc casing dia + 1/4 inches,have a piece of 14 ga. steel 3-4 inches wide cut to circ. length. welded into a circle around plywood disc-use that for the "buck". if you want to leave it in, have it powder coated, if you want to slide it out after the mortar sets, wrap it with poly so it slides out easier.wedge the disc into the center of the steel to keep it round while you close the masonary around it. Works well for arches also. Jim Devier
Jim,
This idea is what came to my mind, too. After the effort of building it and the concern of weight-bearing I'd be inclined to leave it in place afterwards, too. So, powder-coating is a good idea. Furthermore, I'd leave the plywood disc in place and fasten it to the exposed studs to hold the buck in place. Do the stone work, reinforce the studs from the inside, then cut the hole out. Sounds like a plan.
The other response suggested a true keystone arch which still requires the buck. But, its also a considerably larger hole and a greater expense. That decision I can leave up to the client.
Thanks for the advice.
Pascanale
sounds like you got the path. Jim
Zak,
The buck would be temporary until the stone arch was in place. That much I understand. And the corbel design is clear, too. And, as you mention, I do have some concern as to how well the stone was tied into the stud wall. This alone really determines if/how I remove the stone before installing the buck and rebuilding the arch. Good news is that I'd remove the stone in an arch fashion to begin with so there would be some arched support albeit not a keystone fashion. I'd leave the stud wall intact until the stone work was done, then open it up from the inside after sheathing the studs with plywood or cutting a header into the studs.
Another reply is what I was anticipating you'd suggest as an alternative. Have a steel arch fabricated and powder coated since I'd intend to leave it in place. 1/4" steel the full stone's depth. I'd fabricate the brick mold to match this inner radius for the window. Any thoughts on that?
Thanks for the advice. I'm comfortable moving ahead on this now.
Pascanale
How big is this window? Where is it located in the wall, distance from top plate etc. ?
The wall is standard 8 foot height (interior), on a north-facing wall, should be conventional stick framing. The window's location is not specified yet but essentially 3 feet in diameter and would be placed aesthetically beginning about 18" down from the ceiling. There is no second floor and the roof is literally flat (epdm and gravel I think). The house's design in general is a la Falling Water/Frank Lloyd Wright.
Pascanale.