To any architects out there....
I am curious about the type of framing used for multi-storey homes with ashlar stone masonry on the facades. I once read that large homes with ashlar stone walls had to be balloon-framed. I think that it had to do with the expansion and contraction of the frame. Is that true? Or may such structures be constructed using platform framing?
Tim
You're talking about veneer, right? Why would ashlar stone be any different than any other stone, or brick for that matter?
Maybe he is thinking about the need to pick up the masonry veneer load every
2 floors, although the type of framing would not make any difference that I can see. I wouldn't do it with a wood frame anyway. EDS
The only other concern I can imagine is differential expansion vs. framing shrinkage. Balloon shrinks less than western, but I'm not sure of the difference in the coefficients of expansion for brick vs. stone....I would think that brick was lower because of the internal voids but I don't think the difference is large. Western framing shrinkage can easily reach 3/4" or more once you get to three floors, depending on the usual variables.
Stone veneer is not supported on wood framing. The veneer supports itself and is attached to the framing.
As I previously said, going over 2 stories may require the veneer to be supported from the structure and a "soft" joint below the support. This is precisely because of the expansion coefficient differences. All tiebacks must allow for vertical movement.
An example: I was the architect on a team investigating leakage in a Federally owned building in the Boston area that had been built in 1968 with
185' high x 16" thick post tensioned brick piers supported at the base, with no weep holes, tied back to a concrete frame. The concrete frame shrank 3" in 185', and the brick did not. The tiebacks (4x6x1/2" with 1.5" slots) were torn apart in the upper half of the building, and the flashing at the top of the brick was shredded. Why the detailers of this architect's wet dream did not understand differential shrinkage I do not know. $2,500,000 in repairs for bad detailing. EDS
I'm having trouble picturing this...they're freestanding? It sounds bizarre.....
It was bizarre! We consulted a prestressed masonry expert from England who was amazed. The building was by Edward Durell Stone and was to be a cutting edge design for NASA. NASA was moved to Huston after Johnson became president and 120 million in buildings being constructed were left empty. Eventually the Dept of transportation occupied the buildings (It is a campus) and the labs were converted to offices with an increased building occupancy load. After 1974 the building managers cut off the dehumidifying systems to save fuel. This caused a positive vapor pressure into the building walls, trapping moisture behind the brick glazing. As this metro area has over 500 freeze-thaw cycles per year, the brick faces began to pop, a lot. Especially where the sun hit, so the falling brick slices would work around the tower, with the only safe side being North. That's when we got brought in. A very very interesting job. BTW we spot inspected the post tensioning cables and ends and they were in great shape. Major solutions were dehumidifying the building, new flashing, tie backs to the concrete, drilling new weeps, and applying EFIS over the upper third of the tower. This was done 14 years ago and 2 years ago the EIFS was in excellent condition. I've always felt that I improved Stone's building appearance a lot.
So these things were like a super-tall, super-skinny collonade?
Yes, with vertical strip windows between. Shaped like this in section, with post tensioning. Stepped to exterior. Bricks were 4x4x12 with semi-gloss glazed exterior. _______ ___l l___ __ l l___ l o o o l l__________________ l
EDS
Yes, see my section above. EDS
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