Frequently Asked Questions (FAQ)
Q: Can you help me in locating a general diagram in plan and another one in elevation that shows one where the best locations for Expansion Joints &/or Control Joints should be placed in an all masonry building? Your help would be greatly appreciated.
A: Can you be more specific, what kind of building, what is the composition of the envelope, how large is the building, how much modulation is on the elevations and is it a veneer system if so what is the backup system?
In general, you should have Control joints @ 40' oc but that is for a simple plan without modulation. If you are using a brick veneer with a CMU backup system you will need to coordinate the Control Joints CMU will shrink and brick will grow overtime. You also need to isolate locations where steel structure would restrict the movement of the masonry and cause sheer cracking. If the plan has reentrant corners you will need to provide Control Joints at those locations. Avoid Control Joints for approx 4' on either side of a building corner.
And be certain not to hide your control joints behind anything like a downspout for example. Control Joints need regular maintenance and if they are concealed they will be forgotten until they have failed.
Q: I am an architect and I had a technical question about the proper ventilation of cavities within brick veneer walls. Have you ever heard of a case where a cavity space between the brick veneer and the exterior sheathing of the exterior wall would be ventilated to reduce the amount of moisture within a cavity, either by the use of vent holes somewhere in the cavity or by some mechanical means? Is ventilation of the cavity through either of these methods considered standard practice in the industry? Would these types of ventilation systems even be considered desirable within a brick cavity wall?
A: To answer your question there should be a minimum cavity behind your veneer system of 2". At the bottom of that veneer above grade you should provide a mortar bed w/ a flashing the flashing should pass through the veneer and at 24" oc you should provide a weep hole in the head joint of the veneer. You can also provide an equal # of vent holes at the top of the veneer system. The upper vent holes are typical in areas of high wind to reduce pressure behind the veneer.
This system does not reduce the amount of moisture in the cavity it is there to allow any moisture that could be trapped in the system to find its way out with the aid of gravity.
Mechanical ventilation behind a veneer is not required and would present additional problems.
Q: What is the proper method for judging the aesthetics of an exterior masonry wall?
A:Both the Brick Industry Association (BIA) and the National Concrete Masonry Association (NCMA) recommend that you follow the established standards of ASTM C90 for block walls and ASTM C216 for brick veneer walls. Judge most finished masonry walls form a minimum distance of 20 feet under diffused lighting conditions. (Brick veneer walls comprised of Type FBX brick can be viewed from a distance of 15 feet.) You should be perpendicular to the wall, not sighting down the edge of it. The standard requires diffused lighting conditions because direct lighting or a grazing light will magnify imperfections in any flat wall system. You are asked to stand 20 feet away from the wall so that you will view the wall as a whole, not placing extreme emphasis on each brick, block or mortar joint.
Any imperfections that show up from this distance may be significant enough to make it to a punch list.
Q: How should I use a sample panel?
A: A sample panel is used to determine the specific level of quality that is acceptable for a given job.
Q: At what point in the project should the sample panel be erected?
A:The panel should be erected at the beginning of the job prior to the mobilization of the mason contractor. Inspection of the sample panel should take place prior to the masonry contractor commencing work.
Q: What is the minimum/maximum size of a sample panel?
A: The minimum size is approximately 48"x48". The maximum size of the panel is for you to determine. If the panel is going to be large consider having it be a portion of the final work that way the owner will get better value from the sample panel.
Q:How large of a job does it take to make a sample panel worthwhile?
A: You should have a sample panel on every masonry job. Furthermore you should provide construction drawings for the sample panel so that you can be certain to have every aspect of the job that is critical be represented. And by designing the sample panel you will be giving the masonry contractor a line item in their bid that they can identify and you will be certain that it was not overlooked at bid time.
Q: What kinds of things should I specify to be represented in the sample panel?
A: It should incorporate all of the various masonry materials on the job in their designed application. It should include lintels, precast materials, sills, jambs, heads, bond beams copings, weepholes, insulation, ties, wall-anchors at least one outside and one inside corner and an expansion joint. When completed the panel should be cleaned with the specified cleaning agents per the specifications. Cleaning is an extremely important portion of the sample panel and must not be overlooked.
Q: What level of craftsmanship should I expect on the sample panel?
A: It should accurately represent the work that is to be installed. It will not and should not be perfect, construction is not a perfect science but it should be a representation of what is acceptable for that specific project.
