The IBC And Masonry

Tscarborough

I admit that the IBC is meaningless to me, and I have never even looked at it. I use only ASTM, NCMA, and BIA standards. From the stone pillars post, I googled "IBC 1405.6" and this is what I got:

1405.6 Stone veneer. Stone veneer units not exceeding 10
inches (254 mm) in thickness shall be anchored directly to
masonry, concrete or to stud construction by one of the following
methods:

1. With concrete or masonry backing, anchor ties shall be
not less than 0.1055-inch (2.68 mm) corrosion-resistant
wire, or approved equal, formed beyond the base of the
backing. The legs of the loops shall be not less than 6
inches (152 mm) in length bent at right angles and laid in
the mortar joint, and spaced so that the eyes or loops are
12 inches (305 mm) maximum on center (o.c.) in both
directions. There shall be provided not less than a
0.1055-inch (2.68 mm) corrosion-resistant wire tie, or
approved equal, threaded through the exposed loops for
every 2 square feet (0.2m2) of stone veneer. This tie shall
be a loop having legs not less than 15 inches (381 mm) in
length bent so that it will lie in the stone veneer mortar joint
The last 2 inches (51 mm) of each wire leg shall
have a right-angle bend. One-inch (25 mm) minimum
thickness of cement grout shall be placed between the
backing and the stone veneer.

2. With stud backing, a 2-inch by 2-inch (51 by 51 mm)
0.0625-inch (1.59 mm) corrosion-resistant wire mesh
with two layers of water-resistive barrier in accordance
with Section 1404.2 shall be applied directly to wood
studs spaced a maximum of 16 inches (406 mm) o.c. On
studs, the mesh shall be attached with 2-inch-long (51
mm) corrosion-resistant steel wire furring nails at 4
inches (102 mm) o.c. providing a minimum 1.125-inch
(29 mm) penetration into each stud and with 8d common
nails at 8 inches (203 mm) o.c. into top and bottom plates
or with equivalent wire ties. There shall be not less than a
0.1055-inch (2.68 mm) corrosion-resistant wire, or
approved equal, looped through the mesh for every 2
square feet (0.2 m2) of stone veneer. This tie shall be a
loop having legs not less than 15 inches (381 mm) in
length, so bent that it will lie in the stone veneer mortar
joint. The last 2 inches (51 mm) of each wire leg shall
have a right-angle bend. One-inch (25 mm) minimum
thickness of cement grout shall be placed between the
backing and the stone veneer.

Both of these methods sound somewhat poor. Is this the way ya'll do masonry veneers? They do not resemble anything I have ever seen specified, drawn, or installed in 30 years construction in the South, residential and commercial.

__________________
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concretemasonry

Like all standards, it is a minimum standard created by interested parties including contractors, manufacturers, engineers and users/builders. A standard like ACI 530 has no legal power or effect until it adopted by a body like a code authority, agency or specification writer.

It is a minimum and not a how to do it right.

Anyone that cares to spend the time and very, very little money can get involved. It just takes time and patirnce, since standrds are hard to change wthout any documentation or contacts (like suppliers/manufacturers). Average is a couple of years or more depending on the standard updating cyle.

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Tscarborough

That may be true for the IBC but it is not true for NCMA, BIA and ASTM standards. They are not "minimums", they are "best practice".

__________________
It ain't Rocket Science unless you are building rockets.

artisanstone

I've never seen anyone use this method, but I don't see why it's inferior to corrugated ties, for example. I've seen demolition done on brick veneer, and the corrugated ties pull out of the mortar joints rather easily. I would say that one third of the ties pulled out of the backing wall, and two thirds pulled out of the brick work. This is with an excavator ripping large sections off. Stonework does not lend itself to installing these ties with any degree of efficiency (because of the irregular joints), so I can see a wire run along the joint being better and grabbing more. I certainly don't know how one would attach a 2"x2" mesh with nails though.

__________________
Bill Baddorf
Bill@artisanstoneworks.net
www.artisanstoneworks.net
www.stonefoundation.org

tkle

Thanks for enticing me to review my IBC and ASTM Standards. Now I have not only wasted half of my Saturday morning but I am also thoroughly confused and getting a splitting headache...
Basically this is the way I have done it for 30 years using wall ties instead of the wire. I have worked in several parts of California, in rainy areas, extremely cold areas, windy areas, earthquake zones, and combinations of all the above. Having seen many of these jobs several years later, I am assured they will be there until torn down.
Pull them apart with enough force and something has to give. The ties will pull out or fail. They are designed not to fail therefore they will pull out. Under normal conditions they hold.

concretemasonry

The NCMA does not have standards, but does have a series of over 100 TEK Notes. These are written to generall apply with the accepted practice for most of the U.S. The are reviewd by a number of industry people. They are not intened to be totally technically complete, but frquently they cite selected portions of nationally accepted standards and other documents like the IBC. Because of the review/upadting systems, they are not intended to be totally technically accurate at all times because codes change with the times.

The engineering standards always address the specific verionsin effect, although the staff that writes rhe TECK Notes is very active in the preparation of the ASTM and MJSC (ACI 530), which write the material standards and the codes/standards that are adopted or integrated into the final codes like the IBC and IRC. Many of the TEK Notes are educational/iinformative, and are intended to be educational like the notes on staining, efflorescence, sound transmission. These usually are the usual practice, but are not the only solutions.

For most masonry, the codes just refer to the ACI 530 (written by MSJC) since the technical content is beyond a model code. The one thing to look at is the version of IBC/IRC code you are dealing with. They are usually referenced to the latest approved version of ACI 530, which may be released before the IBC is adopted locally. If you look at the structural design of masonry, you will see it generally refers to minimum strenths, or maximum stress, so it is a minimum standard. If you are talking about a stuctural situation, an engineer can use his own interpretation of how the portions of the structure work and design accordingly to probuce a result different from the usual interpretation. That is because it is impossible to write a prescriptive method that works for every situation. This engineer's right can be challenged by a code official, but the engineer with a license can govern because of his license and back-up of the analysis.

ASTM generally has several different type of standards. The METHODS portion of ASTM is very exact because itis used to determine the properties of materials, both for specification compliance AND for comparison to previous testing. There are some minor points that are not specific like the minimum accuraty used to measure a brick or block dimensions. When you get into the MATERIALS part of ASTM, many of the requirements are minimum like the minimum strength for brick or block or any approved gradation for aggrements. In the materials portions there is frequently a provision for an engineer to acceptnon-complying materials if a satisfactory history of use can be shown.

The specification for moratar is really a means to decribe where the lines are drawn between the different types since there is so much overlap of proportions. The mortar spec is a hodge-podge of old tradtions and is an attempt to show why the prescriptive part of the spec (voumes controlling) cannot be used in conjunction of the perforance part (strength controlling). Mortar can be made by the specified proportions may not meet the strength requirements, so the specifier must specify one way or the other, but never both. The appendix of the mortar specs (ASTM 270) does a good job of explaining the tremendous importance of workability over strength. In a block wall, the compressive strength of the mortar has little effect on the strength of a wall.

A little off the point of the original poster, but the examples relate to masonry.

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

tkle

Concrete units being more absorptive than stone requires a greater water retention ratio from the mud. Block walls also expand and contract to a greater degree. Bonding and flexural strength take priority over compression strength. For equal flexibility, the final density of the mortar should be comparable with the material laid.

concretemasonry

The appendix for the ASTM mortar specs says to use the weakest mortar possible to carry the applied loads (compressive, wind and shear). I think the comments attached to the ACI 530 have the same comments.

A similar situation applies to grout where the grout should be about the same strength as the masonry units and there are upper limits on how much stronger it can be. That is the reason grout should never be used to increase the compressive strength of a wall.

The more cement, the more shrinkage since the masonry units are essential cured when laid There is a minor problem since the brick have long term expansion and the cement, concrete and block have a long term shrinkage, which is more compatible with the mortar.

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

Tscarborough

Good stuff. Also, when you are thinking of wall ties for a veneer, the purpose of the tie (sesmic not included) is to hold the veneer OFF the backup, not to prevent it from falling outward.

As noted, all mortar should be specified as weak as required to do the job. Bond and flexural are the 2 important properties, not compressive strength. Portland and sand does not have good bond or flexural properties, it needs something else, lime being the most common.

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artisanstone

I disagree with part of that. The primary function of ties is to resist lateral forces such as wind. These forces may be pushing the veneer toward the backup, or sucking it away from the backup wall. Therefore the ties work both ways. In the case of the wire, the grout behind the stone is performing the function of holding the veneer from moving in the direction of the primary wall, and the tie only has to work in a tensile manner. A common specification I've seen for large ashlar stone that cannot be supported every 2 sq. ft. because of its size, is that the tie system be capable of supporting some multiple of the entire weight of the veneer, if the wall assembly was turned sideways with the veneer hanging from it. This requires some variation of dovetail anchors.

__________________
Bill Baddorf
Bill@artisanstoneworks.net
www.artisanstoneworks.net
www.stonefoundation.org

concretemasonry

A lot depends on whether you have a veneer, which intended to have a space or adhered veneer. If you have grout behind the veneer it is a bonded wall.

Suction is less than the wind pressure, so is usually not so critical.

For a venner, it is ironic that the veneer is usually stiffer than the back-up (wood or steel studs).

__________________
Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

artisanstone

None of this discussion so far is about adhered veneer.

__________________
Bill Baddorf
Bill@artisanstoneworks.net
www.artisanstoneworks.net
www.stonefoundation.org

Tscarborough

"Veneer" is the dirty word. Simply put, a veneer is a finish applied to an underlying structural component.

There are three basic veneer makeups in masonry:

Bonded or Mass Masonry, which means each course is bonded to another using the masonry units themselves as ties. It is structural, and may contain a veneer of decorative units.

Airspace veneer, which provides a 1 to 2 inch airspace between the masonry unit and the substrate. Not structural, and technical to build properly.

Stucco masonry, including adheered veneers. There are many ways to skin this cat.

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artisanstone

And the one you started this post with. Stone veneer not exceeding 10" thickness (not an adhered veneer) with the cavity fully grouted.

__________________
Bill Baddorf
Bill@artisanstoneworks.net
www.artisanstoneworks.net
www.stonefoundation.org

Tscarborough

Technically, that is a cavity wall, you are just filling it with grout instead of insulation, pea gravel, etc.

I am still not clear on why that is a good thing though. Tell me more about it.

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artisanstone

It's not a good thing in itself. With rough large fieldstone of very uneven dimensions, it is necessary to backfill as you go in order to stabilize the next stone you're setting. If you are working with quarried stone that has relatively even bed dimensions, I think you are better off leaving a space. Btw, in the first instance, I don't backfill with just mortar. I use smaller unusable stone carefully stacked with mortar in the same way that the center of a structural stone wall would be built. My bed dimension is determined by the size of my largest stone. It may be between 6" and 8". Most quarried stone is fabricated to 4", so I would work in a 5" bed depth.

__________________
Bill Baddorf
Bill@artisanstoneworks.net
www.artisanstoneworks.net
www.stonefoundation.org

Tscarborough

Parging the backside is a good thing, but filling the airspace does not seem to have any advantages for a non bonded design. Even in dry climates, moisture can penetrate 8 to 10 inches of masonry over the course of a year, and with a veneer, that must be adressed.

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It ain't Rocket Science unless you are building rockets.

artisanstone

It's less than ideal from a moisture management point of view. This is why we're required to use two layers of felt with weepholes to provide a drainage plane. As an upgrade, we offer this. http://www.mtidry.com/products.html

__________________
Bill Baddorf
Bill@artisanstoneworks.net
www.artisanstoneworks.net
www.stonefoundation.org

Tscarborough

To me, that is not an upgrade, it is standard. Moisture barrier, air space, flashed, and weeped. That is standard modern cavity wall construction, hence my confusion with the IBC.

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It ain't Rocket Science unless you are building rockets.

tkle

The IBC tends to change when there has been a problem. Technically this is in issue. In practice it isn't. It's easier, cheaper and it works.