Writing Better Masonry RFIs

Words: Block Design Collective
Photos: Block Design Collective

The RFI process is one of the most valuable touchpoints between contractors and the design team. Whether this occurs during bidding or after award, it’s where questions of intent are resolved before they become field problems. Many of these issues can also be resolved during pre-construction meetings to ensure that all parties are on the same page before the first block is laid. The Block Design Collective (BDC) can provide standard agendas for pre-construction meetings that address the most common areas of conflict.

On masonry scopes, even small clarifications can matter. Details that seem minor can affect production or reinforcement placement once construction is underway. The following masonry details help keep construction predictable from the beginning.

Compressive Strength and f'm Requirements
Compressive strength requirements are one of the most common areas where masonry projects encounter avoidable confusion. Structural notes may specify a required masonry compressive strength (f'm), but that specified strength may not be readily available in the project market and can add cost to projects.

For discussion purposes, f'm is not based solely on the compressive strength of the individual CMU but is instead based on the masonry assembly. TMS 602 provides two accepted verification approaches: prism testing or the unit strength method. The unit strength method uses the CMU manufacturer’s net area compressive strength, tested per ASTM C140, together with the specified mortar type to establish an allowable f'm using code tables, and is usually the easiest method of verifying compliance.

This distinction matters because unusually high specified strengths can affect unit availability, increase costs, and trigger additional testing that impacts the schedule. If the specified f'm appears higher than typical for the wall type, or if prism testing is implied without explanation, confirming the design team’s intent before submittals begin can help avoid downstream complications. The BDC can help design teams by providing “typical” unit compressive strengths for a project market to ensure we are using the most economical materials.

Contractors should also confirm grout requirements at the same time. TMS 402 and TMS 602 require grout compressive strength to meet or exceed the specified masonry compressive strength. If grout strength is not clearly addressed in the documents, clarifying early can prevent field confusion and rework. Grout testing continues to be a major issue in most markets, and there are resources available to mason contractors to ensure that the testing is being performed correctly according to ASTM standards.

Mortar Type Requirements
Mortar type is another area where project specifications can quietly limit constructability. Documents often prescribe a specific mortar type without explaining whether that selection is tied to performance requirements or simply carried over from a standard specification.

TMS 602 requires masonry mortar to conform to ASTM C270 and to match the type and color specified in the contract documents. ASTM C270 permits cement-lime, mortar cement, and masonry cement systems, and in many regions, there are no code-based restrictions on which system may be used. Limitations typically apply only to specific structural elements in higher seismic design categories.

Because mortar type influences material sourcing, batching practices, and consistency in the field, overly restrictive specifications can create unnecessary constraints. Mortar selection also ties directly to testing, and ASTM C270 is clear that compressive strength testing of field-tested mortars cannot be used to determine compliance with the specifications or for approval or rejection.

Movement Joints
Movement joints are critical to masonry performance and are frequently underdefined in project documents. Contractors may see general notes requiring movement joints, but without locations shown in the plan or elevation.

TMS 402 requires that contract drawings include provisions for dimensional changes resulting from shrinkage, temperature, moisture, and creep. In masonry assemblies, movement joints are the primary means of accommodating these movements, and TMS 602 identifies joint type and location as information that should be shown on the drawings.

Movement joints affect more than crack control. Their placement influences water management, reinforcing continuity, flashing terminations, and how masonry interfaces with adjacent materials. Treating joint layout as a field decision rather than a design requirement increases the risk of performance issues and rework.

Wall Intersections
Wall intersections are another detail where design intent should be clearly defined. When drawings do not indicate how intersecting masonry walls are intended to behave structurally, contractors are left to interpret details that can carry high cost and constructability implications.

TMS 402 requires that the size and location of structural members be shown on the contract drawings. The masonry code recognizes three basic wall-intersection conditions: independent walls isolated by a movement joint, walls connected without composite action, and walls intentionally designed to act together as a single structural element.

Many masonry walls are not designed for composite action at intersections. In those cases, simple mesh connections may be used to provide temporary stability during construction without transferring significant forces between walls. Problems arise when drawings are silent on intent, and contractors default to more robust connection methods that aren’t required.

Joint Reinforcement
Joint reinforcement is often specified uniformly across a project, even though not all walls require the same level of reinforcement. Contractors may encounter specifications calling for heavier wire sizes in CMU construction where joint reinforcement is intended primarily for crack control.

Industry guidance for typical CMU walls can often be satisfied using standard joint reinforcement at common spacing. Heavier wire sizes can introduce constructability challenges, particularly when standard mortar joint thickness is assumed. TMS 602 requires mortar joints to accommodate reinforcement thickness, and heavier reinforcement can complicate placement and finishing.

Where joint reinforcement is intended to serve a structural role, such as shear reinforcement in walls that are part of the lateral load-resisting system, heavier reinforcement may be appropriate. These conditions should be clearly identified on the drawings so they can be distinguished from walls where joint reinforcement serves a nonstructural function.

Additional Details Worth a Closer Look
Strap anchors or ties are shown without explanation
Confirm whether force transfer or composite action is intended.

Control joints are shown with continuous reinforcement
Request clarification on whether reinforcement terminates or passes through joints.

Grouted and reinforced cells are not clearly identified
Ask for a wall schedule or marked elevations showing required locations.

Clear design intent is what keeps masonry work predictable. When key details affect how a wall is reinforced or allowed to move, a focused RFI helps ensure the work in the field aligns with the engineer’s assumptions.

The Block Design Collective is available to assist masonry contractors in reviewing plans and preparing informed RFIs. Think of the BDC like having an experienced masonry engineer on call to support your team when questions, big or small, arise.

Menu

Primary Navigation

Quick Links

Writing Better Masonry RFIs

About: Technical Talks

Add a product...

Checkout

Interested in these Special Bundle Deals? Continue to check out

Bonding with Masonry 2026: Q2

The Thirty-Year Mason: Ergonomics as a Retention Strategy

Acme Brick Company Releases 2026 Pocket Guide to Brick Construction

Masonry in the Media: Casa Azul, Chapultepec Castle, & More