I require information about stack bond brick walls when used in brick veneer wall systems with stud wall back up and outboard mineral wool insulation
Brick veneer not laid in running bond is not discussed in the TMS 402/602 Building Code Requirements and Specifications for Masonry Structures. The most information available is on the Brick Industry Association website.
Specific to the installation, BIA recommends reinforcing the veneer with at least one wire embedded in bed joints. This is because stack bond has no in-plane or out of plane structural value. Make sure you use the proper veneer anchor system also. Wall ties are only allowed with wood stud backup. Veneer anchors are required with steel stud or masonry backup. Use brick with the least amount of variation in unit size. The alignment of the units follows the centerline of the head joints. The tolerance for the variation in length for a modular size FBX brick given in ASTM C216 is +/- 5/32". The variation in straight and plumb within the same parameters. All of this information must be written in the specification and a mockup should be required as well. Call me if you need to.
Jerry Painter, FASTM, CGC, SMC
Are control joints required in CMU structural backup walls in double wythe cavity systems with brick veneer on the exterior, drywall on the interior and a drainage plane between the two wythes?
Quote from the Control Joint section of NCMA TEK 10-01A - “Because shrinkage cracks in concrete masonry are an aesthetic rather than a structural concern, control joints are typically only required in walls where shrinkage cracking may detract from the appearance or where water penetration
Control joints in the CMU wall are there to accommodate movement of the wall due primarily to shrinkage of the concrete block. Uncontrolled cracking, when visible, is unsightly and when exposed to wind driven rain may allow water to enter the wall and possibly the interior of the building. The control joints both hide the cracking for aesthetic reasons and concentrates the movement in a location (the control joint) where waterproofing can be easily applied to prevent water from entering through the joint into the structure.
Double wythe cavity walls containing a drainage plane between the two wythes offer the unique feature of both visually covering the CMU backup wall and preventing wind driven rain from reaching the backup wall. As stated in TEK 10-01A this eliminates the two main reasons for incorporating control joints into the structural backup CMU wall.
In making the determination to eliminate control joints in the structural masonry backup of a double wythe cavity wall it is important to ensure that the section of wall will indeed be neither visible or subject to exterior weather. Particularly in long sections of wall, the elimination of control joints in a single area of the wall may produce additional stress, and thus larger more pronounced cracks, in an adjacent section of the wall exposed to visual sight or weather.
Control joints may also have a structural purpose, thus elimination should not be done without the knowledge of the structural engineer for the project.
I am building a new 3600 sq ft(a/c) single story house in Palm Beach Country Estates, Palm Beach 33418. The lot is just West of the Turnpike and I95 ( approximately ten miles inland from the ocean). My Architect has asked if I want to use a bond beam or a tie beam as I am building further inland. I have always built with tie beams but those structures were East of I95 and closer to the ocean. The concern is obviously structural strength and roof security in relation to hurricanes. I am aware of the structural advantage of a tie beam but how do bond beams compare?
What do you see as the cost advantage?
Are there any design specifications that should be included?
Yes, the formed and poured concrete tie beam is stronger. Do you need the extra strength and is it worth the money? I say NO and NO. Masonry bond beams can be designed to meet all loadings and wind speeds. A standard South Florida bond beam is going to have 2-#5 or 1-#7 bar in the top course with the top two courses grouted solid. The bottom grouted course would need to be reinforced over all openings and the amount of reinforcement would depend on the roof load and span of opening. The new ICC 600 give direct guidance and I would suggest you secure a copy to have all the latest design information for south Florida wind loads.
It is also available online for viewing at https://codes.iccsafe.org/content/ICC6002020P1
All other reinforcement is approximately the same.
As far as cost difference, your local builder is going to have to give you that info. Most So Fla contractors are intimately familiar with both types of construction.
The most important items are that your bond beam (either one) is solidly hooked down to your wall at the spacing of your wall steel and that your bond beam (either one) is laterally supported by the roof system, particularly at the gable end (if there is one). I recommend a hip roof that supports your bond beam or tie beam at the entire length.
I have viewed a LOT of hurricane damage and have not seen a properly designed masonry bond beam that failed OTHER THAN a failure of an single course 8” deep bond beam. I do not recommend 8” masonry bond beams (or 8” poured tie beams!). There is not enough embedment for the vertical hook to develop into the beam.
Don Beers, PE, GC
How do you control the grounds (stucco thickness without casing) Additionally, do you need casing to separate dissembler materials?
There is nothing in the code that prevents you from putting in additional casing and control joints. The misconception that we wanted to dispel is that control joints are “required” by the code in direct applied stucco at locations other than where you find control joints in the substrate. I would reinforce the potential leakage problem inherent with all installed stucco joints. Proper detailing of joints is essential for a leak proof stucco coating. As you mentioned there should be a joint at dissimilar materials.
What is the best mud-set mortar system for the support of heavy masonry pavers that are being used on a circular drive way with heavy vehicular traffic….Fire engines, Airport buses, Vans and large, expensive SUV’s and Pick-up trucks?
“Best mud-set mortar system” is a red herring because you don’t "mud set" or grout pavers unless it is for looks – like a pedestrian path you want to look like a brick wall laying on the ground. For heavy traffic applications you place the pavers on a sand bed over a concrete or compacted road rock base. Then you fill the cracks between the pavers with sand. The shape of the pavers and the sand cause them to interlock (which is where the name “interlocking pavers” comes from).
Grouts used in heavy traffic application are subject to crushing and subsequent failure so are avoided.
If you put the pavers over a solid concrete base you have to include weep holes to drain away the water.
For circular patterns where you encounter radial forces you want good "in plain" interlocking to prevent shifting and a herring bone pattern is usually recommended.
The contractor on our job is pointing out small cracks and holes that need to be repaired/filled etc. I have been in the masonry industry for half a century and respect good workmanship but I think the imperfections that the contractor is pointing out are not significant or reasonable.
The wall is to receive direct applied stucco thus we are cutting the joints flush.
My question is - what are the criteria for judging whether or not an imperfection in a masonry wall should be acceptable.
The simple answer is that unless the specifications specifically call out for a special criteria for workmanship the codes contain one universally accepted criteria – view at 20 ft under diffused lightning. Period. This is in section 7.2 of ASTM C90-14. The current version of C90 referenced in the 7th Edition Florida Building Code is 2014.
It is understood that full head joints and bed joints are called out in the TMS 602 Code (current referenced edition is 2016) but there is no further guidance given. A mock up panel, if built and agreed on prior to construction, would govern for workmanship. In the absence of a mock up panel you are left with that most rare of commodities – common sense.
So, on the basis of common sense lets think about where our only code based criteria, 20’ in diffused lighting, might or might not apply.
It probably wouldn’t apply for the installation of a glazed block in an 8’x10’ bathroom. In that case your mortar joints are going to be expected to approach perfection. Any imperfections are going to be visible. Since the joint is tooled the mason at least has a fighting chance of striking the joints with a high degree of care.
Our 20’ criteria is regularly used for architectural block in an exterior wall. Cracks and holes that are not visible at 20’ under diffused lighting are considered acceptable.
In the case of block substrate to receive a direct applied stucco coating the 20’ criterial would be considered adequate for several reasons. The first is that the joints are not tooled. The joints must be cut flush so that they do not reflect through the finished stucco. Without tooling complete densification of a mortar joint is not possible. The second reason is that the direct applied stucco is the exterior weather barrier. There should absolutely be a solid block and filled mortar joint behind the stucco but the stucco itself is your primary protection. The third reason is that there are no esthetics issues.
My view is that without a mock up panel and without job specifications specific to the appearance of the mortar joints, the 20’ diffused lighting rule would govern as the only applicable code guidance.
There were provisions to use a fill material for hollow units to increase the fire resistance rating. In past, materials like zonolite (vermiculite) were used and a 6\" filled hollow unit would provide over 4 hours of fire resistance. Due to asbestos issues, vermiculite is no longer used. Is there a similar product that can be used?
The fill material could be a variety of material, The key is what the CMU is manufactured with. If the 6" CMU is manufactured using sand and/or limestone aggregate you cannot reach a 4 hr equivalent rating. What you fill the cores with takes on the rating as the CMU. Full lightweight CMU with cores filled will meet a 4 hr requirement. A proper blend of sand and lightweight with filled cores may meet 4 hrs. The blend will have to be verified by an independent lab. Fill material can be practically anything that is fireproof itself. Perlite, sand, expanded clay aggregate and masonry cell fill (course or fine grout) are possibilities.
The Masonry Society has an excellent book on Fire Resistance of Masonry. Chapter 7 Section 722 covers calculated fire resistance in the IBC. I am attaching a link to the NCMA TEK that covers the same subject.
FIRE RESISTANCE RATINGS OF CONCRETE MASONRY ASSEMBLIES - NCMA
Thank you for contacting the MAF. Our goal is to make sure that when masonry is designed and installed correctly the public has the best wall system available.
Jerry M Painter, FASTM
I have a non structural 8\'\' CMUvFire Wall approx. 38\' long x 12\' high, it is reinforced with a BB at the top with 2 # 5 bars and vertical every 32\'\' # 5 bar. I asked the question if a vertical control joint would be needed in this wall, as nothing was shown.
The response was to seek the advice as to what is recommended, can you please advise?
Thank you for contacting us with your question. TMS 402/602-16 (Building Code Requirements and Specification for Masonry Structures) does not address locating control joints (CJ) in concrete masonry walls. In the Commentary for TMS 602 in Figure SC-7 on page S-51 samples of constructed joint types are shown. The figure for a Fire-Rated Control Joint is the one to be used. I would highly recommend placing rebar and grout in the cells on either side of the CJ. In TMS 602 Part 2 the commentary for sections 2.5 A&B it is recommended to use NCMA TEK 10-02D. This is the Empirical Method for determining the location of CJ in concrete masonry walls. It gives a ratio formula of 1.5:1 or not to exceed 25lf maximum. In your case that is a 12'-0" high x 38"-0" long wall. Using the ratio the spacing would be 18'-0". One CJ would not be enough and 2 would be required. They could be placed as the architect decides or if he does not locate them you could decide the location based on panels not to exceed 18'-0". I would personally put a 17'-4" panel centered and a 5'-4" panel on either side because that would be modular blockwork. There are two additional TEKs that could be reviewed by the architect. They are TEK 10-01A which is a general discussion of control joints in concrete masonry and TEK 10-03which is the Engineered Method. A quick rule of thumb is locate a CJ at any change of the mass of the wall and/or not to exceed 25'-0".
I hope this is helpful. Thank you for contacting us and using one of the many services available. You can call me at 352-494-8955 if necessary.
All COLORED block made in Florida Contains integral waterproofing. The assumption you MUST make is that if the block is not colored it will not contain integral waterproofing. EVERY block that is used in a single wythe installation SHOULD contain integral waterproofing --- even if it is going to be painted or sealed. So…. If you are designing a single wythe wall that does not contain integral color be sure to request integral waterproofing!! ONE more thing --- EVERY single wythe wall SHOULD be painted or sealed.
Remember – Single Wythe -- Integral Waterproofing --- Painted and Sealed -- ALWAYS.
Jerry Painter, FASTM
Don Beers, PE, GC