Masonry project specifications can be intricate and complex, especially for masonry contractors, often requiring a high level of attention to detail and subjective interpretation. The format of project specifications follows the same format set forth by the Construction Specification Institute (CSI) and is broken down into three parts. These include General, Products (materials), and Construction.
The governing building standard for masonry TMS 602 Specification for Masonry Structures follows the same three-part format. The three-part format of TMS 602 was intentionally developed so that it would parallel the CSI format, which is the basis for the layout and content of project specifications.
Project designers will either outsource or internally task specification development without direct involvement in the process. The biggest drawback in this process is that specification writers typically follow the practice of cutting and pasting the entire masonry specification with only a cursory review. Any inaccuracies in previous project specifications will be transferred to the new project when cutting and pasting. Additionally, because every job is unique and singular, provisions that applied to a previous job will not necessarily apply to the job at hand.
When developing field and design documents, assumptions and ambiguities can lead to problems with interpretation by the contractor. Design and contractor interpretations may not always be the same.
Although certain provisions may be clear to the designer, the contractor may interpret those same provisions based on experience rather than designer intent. Holding a pre-construction meeting provides the opportunity to clarify any questions by the contractor and the designer about design intent, job functions and responsibilities. While not a code requirement, a preconstruction meeting of interested parties can resolve issues or questions before construction begins instead during the construction process.
Also problematic with project specifications is keeping up-to-date with the requirements of ASTM Standards. Each Standard has a dash after the Standard designation; for example, if a standard was published in 2017, it will have a dash 17 next to it, as in ASTM C90-17. If the Standard is published more than once annually, it will have a letter added to the year designation (C90-17a or C90-17b).
To illustrate this point, ASTM C90-13, Standard Specification for Loadbearing Concrete Masonry Units, required 1,900 psi as the minimum average compressive strength of concrete block. The next year, ASTM C90-14 required 2,000 as the minimum average compressive strength of concrete block. Without a specific year reference of the Standard, there is confusion on minimum required compressive strength of the concrete block.
Contractors should be aware that designers often insert provisions in project specifications that are already part if the Code or material Standard. This redundancy can be a result of a problem encountered on a previous project so the designer wants to be clear that the contractor understands the specific requirement. The drawback is that with cutting and pasting, as the Code or Standard may change, the provisions contained in the specification may become obsolete or actually conflict with current Code or material Standard requirements.
Even today project specifications contain Grade and Type requirements for concrete masonry units conforming to ASTM C90. Unfortunately, the Grades were deleted from the Standard in 1990 and Types deleted in 2000 in favor of the more stringent requirement.
Mortar is another masonry component that is frequently overspecified. Many designers believe that every masonry component must be at least as strong as the masonry system strength.
While this is a logical assumption, it does not hold true for masonry mortar. Mortar is not the weak line in the chain.
There are 3 ASTM Standards relating to masonry mortar; ASTM C270, Standard Specification for Mortar for Unit Masonry, ASTM C780, Standard Test Method for Preconstruction and Construction Evaluation of Mortars for Plain and Reinforced Unit Masonry, and ASTM C1586, Standard Guide for Quality Assurance of Mortars. All three Standards state multiple times that field tested mortar (often blended by proportion) should not be tested for the strength values (property requirement) listed in the table in ASTM C270. As indicated in that table, the values are for laboratory prepared mortar.
In an effort to get the best of all, designers will specify that mortar meet certain proportion criteria and at the same time, meet minimum compressive strength property requirements. This is in direct conflict with the provisions of the mortar Standards listed above and one of the most overspecified masonry issues.
When tested, the masonry mortar specimen is cast into a 2 inch cube or a 2 inch by 4 inch cylinder. Both of these forms do not absorb water. The combination of the masonry unit absorbing excess water from mortar as units are laid, along with the much stronger aspect ratio of a 3/8 inch tall mortar joint, contribute to a misrepresentation of tested mortar compared to strength of a mortar joint in the wall.
“I recommend that designers not over specify,” said John Chrysler of the Masonry Institute of America. “Redundancy isn’t necessarily a good thing unless there’s a good reason for it.”
Problems That Mason Contractors Experience
Normally, contractors will follow the path of least resistance. For example, when project specifications list both proportion and property requirements, the contractor will try to provide both rather than requesting of clarification on which of the two methods will be acceptable to show conformance, by taking a risk that mortar will meet both the property.
Another shortcoming that mason contractors experience is the inability to be up-to-date with existing codes and standards. By staying up-to-date, mason contractors can obtain considerable information regarding standards that could be of help with future projects.
Even though the basic installation of masonry, one unit at a time, has not changed in generations, Codes change every three years and material Standards even more frequently. Contractors should keep up top date with the requirements since many changes work to the contractor’s advantage.
In the ASTM C90, which is the standard for concrete block, at project completion the inspector, owner, or architect might declare that the blocks are not perfect. The next step would be for them to approach within feet of the wall and start analyzing it while also picking it apart.
The inspector, owner or architect may criticize the quality of installed concrete block during construction progress. This visual observation may be at a distance of two feet. Contractors should be aware that the designer cited ASTM C90 as the criteria for concrete block and there are provisions for tolerances and acceptability. ASTM C90, Section 7.2 states that exposed concrete block is to be viewed at a distance of 20 feet under diffused (indirect) lighting for acceptability. The same section also references acceptability of chips in concrete block.
The inspector, owner, or architect need to understand what the benefits are for the standards. In order for them to understand these standards, they need to comprehend what these standards are.
If they understand what is in these standards, they can be a powerful force when it comes to backing and advocating the information that comes down from the designer.
The designer, contractor and inspector all need to fully understand the requirements contained in the applicable Standards of the project. When there is misunderstanding or partial application of the Code or Standard, the informed contractor should diplomatically discuss issue and if there is still no resolution, then an independent party familiar with masonry requirements should be consulted.
When a contractor is not immediately familiar or is unsure with how a project proceeds, they move forward with how a certain way that they feel it should be done rather than inquiring as to the best method.
Contractors that proceed with the project when there is uncertainty or conflict with the project documents will likely lead to problems during the course of construction. Once built, correcting installed masonry is difficult, if not impossible. If the designer is not satisfied with the installed work, the outcome is never acceptable. The two obviously outcomes are that the project ends up in litigation and that the designer will never specify masonry again.
Avoiding Masonry Problems Moving Forward
Preventing what a designer does is not something that can be altered. New designers will put information on the specification documents based on what they feel fits best. Moving forward, it’s essential for them to ask questions in order to solve the uncertainties that are bound to exist.
Preventing what a designer has done or specified is not easily altered. Communication with the designer prior to construction will bridge the gap between design and construction. Young designers will specify information based more on what they have been taught, not on experience. Going forward, the contractor should communicate with the designer explaining the construction possibilities and drawbacks and at the same time the contractor needs to listen to the designer to understand the design requirements of the project. This is a form of education for both the designer and contractor.
As always, quality and effective communication is essential. The best way to do this is to meet with all parties involved and share needs and expectations. This approach is beneficial for the designer and contractor in both the short and long term.
By applying these principles, mason contractors can avoid problems they might run into and ensure a successful job for the client.