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… See illustrations below:
“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.
I am always hearing about the Perm Rating of walls and wanted to know if perm rating of masonry walls is something that is a big concern in Florida?
The Perm rating of stucco is a red herring. Climate zones 1 and 2 strictly LIMIT the perm rating of vapor barriers because you don’t want to trap moisture in the wall. Standard stucco is a Class III Vapor Barrier with a perm rating between 5 and 10 which would also make it a Vapor Permeable which is better yet in Florida. Stucco is accepted as a suitable weather barrier throughout the code – and that is what you are looking for in climate zones 1 and 2 – a weather barrier – not a vapor barrier. Check out 1405.3.1 and 1405.3.2. The code is RESTRICTING the perm rating of vapor barriers – not requiring low perm barriers. Stucco, and CMU, serves as a good weather and air barrier. If you are keen on low perm vapor barriers then move up North. We don’t need them in Florida.
Correct code to use to certify CMU for a project designed under a previous edition of the FL Building Code.
Our project calls for 2 hr rated block and was permitted under the 2010 FL Building Code. The engineer is not approving our submittal because the manufacturer is certifying the block under the 5th Edition, 2014 FL Building Code. He is saying that the block must be certified and tested under the 2010 code? What is going on?
Your reviewing engineer is being a bit obsessive over a moot point. Table 721.3.2 in the 2007 FBC with 2009 revisions is EXACTLY the same table as 721.3.2 in the 2010 FBC which is EXACTLY the same table as 722.3.2 in the 5th Ed FBC which is EXACTLY the same table as 722.3.2 in the current 6th Ed FBC. And I do mean EXACTLY the same table. There have been no changes in this table for the past 30 years or more. 4 inch Eq Thickness of limestone agg gets you a 2 hour rating in 2007 and in 2019 - period, end of story. Additionally, the C140 testing procedures have remained exactly the same over the same 30+ years. The project was permitted under the 2010 FBC and thus is ALLOWED to be constructed under the requirements that governed at the time it was designed and reviewed (so you are not required to completely redesign the project under the current codes). It is my understanding that this does NOT mean that everyone supplying materials to the job have to climb into a time machine and retro backwards 10 years to resurrect and construct the job by historical - and out of date - standards.
That being said, your standards in the certification are not correct either way (neither 2010 or 2017. My view is that you should be testing and certifying your product under the current code (2017) and that the engineer of record should accept the current codes and standards governing construction in Florida. The question is moot because the governing procedures, and tables, have not changed.
Don I have a GC client that’s asking me a question that I cannot answer.
For a 1 hour / non load bearing masonry wall that would be between two floors, do you need to have any special caulking (fire or other) at the top on the masonry wall, besides the mortar joint.
This is new to me so let me know your opinion on this.
As long a there is a full mortar joint the face shell thickness on both sides of the wall there should be no question about the overall fire rating of the wall. Consider that the entire wall is FILLED with joints filled with mortar the face shell thickness of the wall. The joint at the top of the wall would be no different.
I am building a home in the panhandle and am having an argument with my architect on how much insulation to add to the walls. Do you have some basic rules of thumb I could use in determining insulation requirements?
Most of the energy lost in a home is through the infiltration of outside air into the house, the hot water heating system, the efficiency of the AC unit, heat gain through the ceiling from the attic space and through the windows. The opaque exterior walls really do not contribute that significantly to the heat gain/loss, usually in the range of 6% – 10%. That being said, a modest amount of well-placed insulation can pay for itself in 2 – 3 years of energy savings.
The most common type of masonry insulation is foil backed paper stapled between the furring strips. This adds about an R3 of insulation and is the minimum amount recommended. The great thing about Florida is your temperature gradient is, by and large, small – usually less than 20 degF and for much of the year less than 5 degF. The maximum insulation recommended anywhere in Florida is ¾” Poly Iso with a foil backing. The non-foil side is glued or attached directly to the masonry and the furring strips go directly over the foil backing creating a ¾” reflective air space between the foil and the drywall. This arrangement gives you an approx. R7.8. You might want to use this on a large expanse of west facing wall where the heat gain in the afternoon can be more intense.
Any more insulation than the R7.8 is a dead loss money wise and will NEVER pay for itself in energy savings. You can prove this to yourself by simply running the analysis in Comcheck or energy gauge software. You will quickly see that the exterior walls are not where your energy loss occurs.
We have a project in WPB, the plans are calling out a Compressible Bond beaker at the control joints. We did not include this (Rubber, PVC CJ) in our contract, however, we did account for leaving the 3/8” of an inch as gap the control joint. Our walls are 8” CMU with a 2 hour fire rating.
The EOR indicated that he wanted the joint to be 2 hr fire rated.
My question is what determines the use of a rubber or PVC material verses the 3/8” gap for a control joint?? Are either of these fire rated?
Please see the attached detail and EOR response.
A "compressible bond breaker" in a control joint, as shown in his detail, would mean a backer rod. The backer rod or "compressible bond breaker" is pushed or "compressed" into the joint prior to caulking the 3/8" joint. It's purpose is to control the amount of caulking that goes into the joint, but more importantly, to "break" the 3 point "bonding" that occurs in the back of the joint and thus prevents the caulking from tearing open at this location.
The EOR is confused about the need for a COMPRESSIBLE material. He does want a fire rated system which is not what was called for either in the plans or in his response. His detail does not call out for a key way so that is clear. But it simply does not indicate what he is asking for. The language, as I have said, is simply another way of asking for a backer rod which he has already shown. He needs to go to https://submittalwizard.3m.com/# and pick a caulking that will give him the 2 hr rating he desires. A piece of "compressible rubber" does not carry a 2 hr fire rating. Whatever is in the control joint does NOT have to be compressible because the joint will never be compressed. Conc masonry walls shrink - always. He may be thinking about a clay brick product that would be EXPANDING and thus compressing the joint. You can fill masonry control joints with mortar if you want because they DON'T COMPRESS. Brick expansion joints have to be completely clean of mortar because the wall expands and the joint does get compressed.
At this point he could solve the problem by simply changing to a fire rated caulking and eliminating the rubber filler. What he is asking for in his response carries no fire rating and is not what the words on the plans say.
Another solution would be to provide a min of a 2" deep mortar joint on each side of the wall. After raking out the mortar for your backer rod and caulking you would have the usual 1 1/4" of mortar left in the joint - the same as every other head joint in the wall. This would meet the 2 hr rating by simply matching the amount of mortar as every other joint in a typical 2 hr masonry wall with face shell bedding. You would not have to go to the extra expense of using a fire rated caulking.
I would be happy to discuss this with the EOR. Proper control joint construction is an area of common misunderstanding. It was nice to see that he had actually bothered to include control joints, an essential part of preventing random masonry cracking.
Detail for Compressible bond breaker detail.docx
Do you know if there is a guide to residential construction in Florida? I have been asked a couple of times about one.
I refer you to R302.2.1.1 linked below. In NE Florida you can still use the MAF Guide if you are nestled into an cozy residential development and can argue Cat B – but only up to 130 (see fig 301.2(4) below). 115 doesn’t hit the state at all and the only reinforcement provisions in the FBC Residential - Chapter 6 are for seismic cat C and D (and there is no seismic in Florida). The rest of the masonry stuff in Chap 6 is just spec stuff better left in TMS. So, for the rest of Florida your best guide is the ICC 600.
We are building a project with 9’ 4” walls. The walls have vertical steel in poured cells at 16” on center and a single 8”x8” bond beam one course down from the top of the wall. The top course is regular block with only every other core grouted above the vertical poured cells. We would like to pour this wall in a single 9’ 4” lift however the building official is telling us we must pour the wall in 5’ 4” lifts because of the bond beam one course down from the top.
The salient code section governing this discussion is out of TMS 402-2016 Section 3.2.1 and TMS 602-2016 Section 3.5 D – Grout lift height. A copy of these code sections is attached to this blog (I hope). Since the 2008 TMS 402/602 we have been allowed to grout up to 12’ 8” in a single lift if three conditions were met: 1) the masonry was at least 4 hours old, 2) the grout was fluid – 10-11 inches and 3) there were no intermediate bond beams to be grouted where we would need the grout to flow horizontally to fill the bond beams.
The next section of the code (3.5 D.1.b) tells us that if the first 2 conditions are met and we have intermediate bond beams we can grout to the bottom of the lowest bond beam above 5’ 4”. In this case that would be 9’ 4” subtract 16” or 8’ of height. So, by the book, we would place an 8’ lift then come back with a second pass and grout the bond beam and the course above.
The normal spacing of vertical and horizontal bond beams is 48” oc throughout the seismic regions of the country. In Florida we do not have the minimum 48”x48” seismic grid requirement and our bond beams are normally at the top of the wall. Thus, the code is written to ensure that the grout will flow at least 24” into any horizontal bond beam. In this particular case the grout need only flow 4” horizontally into the horizontal bond beam (remember the poured cells are only 16” on center).
It would be my hope that in this particular case common sense would prevail and the inspector or EOR would ignore the intermediate bond beam realizing that 1) it is virtually at the top of the wall and 2) the horizontal flow is MUCH, MUCH less than the distance that the code is set up to accommodate.
Failing common sense, section 3.2.1 of TMS 402-2016 provides for a solution through the use of a demo panel showing that the variance from the code does not affect the ability of the contractor to solidly grout the spaces in the wall receiving grout. The commentary to Section 3.2.1 gives additional guidance on the demo panel.
We are a residential engineering and design company in Central Florida, and have several builders inquiring about removing as many grouted filled cells as possible to reduce cost. They comment that we are more conservative than our competitors. We have completed our own wall calculations based on TMS 402-13 (and confirmed with NCMA software), and are comfortable with our grout filled cell spacing calculations; however, the code is less clear about filled cell requirements around openings. Some of our competitors only place a filled cell (typically with (1) vertical #5 bar) on one end of shorter window and door openings. I’ve heard several engineers cite FBC 222.214.171.124 (see below), but of course this is only for High Velocity Hurricane Zones, and that section has several other requirements for “tie columns;” namely 2126.96.36.199 & 2188.8.131.52. In my view you can’t follow one section of the code, and ignore the others.
I’ve spoken to plans examiners and inspectors, who cite Figure R606.11(1) showing reinforced filled cells on both sides and above and below openings; however, this section is prescriptive, deals with anchorage, and has unclear requirements (“Wind loads less than 30 psf,” is that design or ultimate pressure?).
The most relevant code citations I can find are in R301.2.1.1, which points me to FBC, Section 2107: Allowable Strength Design, which references back to TMS 402-13. I can’t find any clear-cut requirements about reinforced filled cell placement around openings. Assuming we don’t need the reinforced filled cell for the loading requirements, or buck fastening, is there a code citation, construction guide, white paper, or other source we can reference regarding filled cell requirements around openings. If not, what is your view as far as best practices or typical industry standards.
Referenced code section:
When openings are between 3 and 8 feet (914 mm and 2.4 m) in width, such openings shall have one #5 vertical reinforcing bar at each side. The vertical bars shall be placed in concrete filled cells and shall extend into footings and into tie beams. All such bars shall be continuous from footing to tie beam. All splices, where needed, shall be 30 inches (762 mm) minimum.
Tie columns shall be not less than 12 inches (305 mm) in width. Tie columns having an unbraced height not exceeding 15 feet (4.6 m) shall be not less in thickness than the wall or less than a nominal 8 inches (203 mm), and, where exceeding 15 feet (4.6 m) in unbraced height, shall be not less in thickness than 12 inches (305 mm). The unbraced height shall be taken at the point of positive lateral support in the direction of consideration or the column may be designed to resist applicable lateral loads based on rational analysis.
Tie columns shall be reinforced with not less than four #5 vertical bars for 8 inch by 12 inch (203 mm by 305 mm) columns nor less than four #6 vertical bars for 12 inch by 12 inch (305 mm by 305 mm) columns nor less reinforcing steel than 0.01 of the cross-sectional area for columns of other dimension nor less than may be required to resist axial loads or bending forces. Vertical reinforcing shall be doweled to the footing and splices shall be lapped 30 bar diameters. Columns shall be tied with #2 hoops spaced not more than 12 inches (305 mm) apart.
Great question: Short answer - up to the registered engineer or architect - not specifically addressed in any code that would usurp the judgement of the design professional....period.
Lets start with section 2121 of the 6th Edition FBC - Building. These are historic prescriptive requirements and there has ALWAYS been confusion as to where and how they apply. Thus, we (the industry) inserted the following section into 2122 - Reinforced Unit Masonry - to try and drive home that 2121 just does not apply to masonry designed in accordance with the provisions of TMS 402/602:
The provisions of TMS 402/ACI 530/ASCE 5 and TMS 602/ACI 530.1/ASCE 6 are hereby adopted as a minimum for the design and construction of reinforced unit masonry. In addition to TMS 402/ACI 530/ASCE 5 and TMS 602/ACI 530.1/ASCE 6, reinforced unit masonry structures shall comply with Sections 2122.2 through 2122.10.
Section 2121 shall not apply where design and construction are in accordance with the provisions of this section.
Thus you are completely correct that the provisions of 2121 are unique and independent and offer no guidance in properly designing your masonry structure - unless you want to use them in their entirety in designing your structure.
Ok, now to the residential code. Not much help there. As you indicated, Figure R606.11(1) shows some interesting stuff but nothing that gives you the guidance you, as a designer, are looking for.
The provisions calling for steel girding all openings is a seismic provision dealing primarily with shear. For shear in residential wind design you are generally going to distribute your shear to solid wall sections depending on their stiffness and utilizing only the un-reinforced value of masonry. If your un-reinforced shear value of the individual solid panels is not sufficient and you have to design a reinforced masonry shear wall you would generally be reinforcing around all sides of openings --- but --- that is almost never going to be the case with residential design based on wind (Florida has no seismic requirements) - and is rarely the case with low-rise commercial design. Bottom line is you are generally not going to see masonry under an opening unless it is there for crack control (not structural reasons).
R301.2.1.1 references the ICC 600 in which section 405.3.2 "Openings in Masonry Walls" gives some common sense guidance to put a bar on either side of openings over 6' wide and to make sure that any bars interrupted by the opening get distributed to both sides. For openings in residential structures this is about as good as it gets.
For large openings you have to make sure that the wall segment on either side will take the out of plane bending load from 1/2 the opening width. Where you have a number of large openings in a row this can be challenging.
Obviously, you are always going to put a bar over the opening.
I always recommend placing a vertical # 5 at all corners. Although this is not a code requirement it is standard practice. I also place a vertical #5 on either side of control joints – not a code requirement either.
What is the acceptable vertical tolerance allowed in CMU and brick construction?
1/8\" in 10ft and 1/4\" in 20ft?
Acceptable vertical tolerances in cmu and brick are covered in TMS 402/602 Building Code Requirements and Specification for Masonry Structures. The specific location is TMS 602 Part 3 paragraph 3.3 F.2.b. It allows for a +/-1/4" in 10 lf, +/- 3/8" in 20 lf and a 1/2" maximum. Remember when checking these tolerances that the TMS 402/602 may not be the best from an atheistic standpoint. The architect can put tolerances in the project specification that are more stringent than given in the code. They may also reference documents from BIA or NCMA. Read your specifications very carefully to insure that what is stated in the specifications won't require workmanship of a higher level (more costly). Brick workmanship should always be approved using a mockup.
Remember!! There is no ASTM standard for acceptable masonry workmanship.
Jerry Painter, FASTM
Don Beers, PE, GC