A screen block (also known as a breeze block) spec sheet should confirm five key things: structural performance, fire performance, salt and chemical resistance, recycled content for LEED projects, and material composition, including silica content. Together, these fields distinguish independently tested engineered products from unverified decorative masonry. This guide explains how to read a breeze block spec sheet and what each field means during product evaluation.
Key takeaways
- Not all breeze block spec sheets are independently tested. Look for recognised test standards and laboratory certification, not manufacturer-estimated values.
- ASTM C140/C140M is the correct testing standard for decorative masonry units. ASTM C90 applies to structural concrete masonry units (CMUs).
- BS 476 Part 7 Class 1 measures surface spread of flame and should be presented alongside the fire performance requirements for US projects.
- LEED projects should look for ISO 14021-verified recycled content, rather than manufacturer-declared sustainability claims.
- Crystalline silica content below 1% can reduce the OSHA 29 CFR 1926.1153 compliance burden during installation.
- Breeze block dimensions are often listed in metric sizes, so check dimensional tolerances and joint sizing when specifying for US projects.
For US architects reviewing breeze block submittal requirements, these are the key spec sheet fields to compare across manufacturers
Why ASTM C140 matters — and how it differs from ASTM C90
ASTM C140/C140M-24a is the correct testing standard for decorative masonry units, including architectural breeze blocks. It measures key performance characteristics such as compressive strength and water absorption. By comparison, ASTM C90 applies to structural concrete masonry units (CMUs) used in load-bearing construction. Although both are masonry standards, they serve different purposes. Specifying ASTM C90 for a decorative screen block applies the wrong performance standard. Jonite cites ASTM C140 breeze block certification as the appropriate benchmark for evaluating decorative architectural masonry units.
BS 476 Part 7 Class 1 — what this British fire standard means on a US project
BS 476 Part 7 measures the surface spread of flame, with Class 1 representing the highest performance classification under this standard. If you're reviewing a BS 476 fire rating on a US project, it should be treated as supplementary fire performance data rather than a US code-compliance standard. It can be presented alongside project-specific requirements such as ASTM E84 or NFPA 286, but not as a substitute for the project's required fire testing. This is particularly relevant for commercial and hospitality facades where fire performance is an important design consideration.
Silica content — why this field belongs on every spec sheet you evaluate
Crystalline silica content directly affects the level of OSHA compliance required during installation under 29 CFR 1926.1153, the US construction silica standard. Standard concrete typically contains 15–25% crystalline silica, while Jonite's engineered stone contains less than 1%. OSHA requires employers to assess and control worker exposure when respirable crystalline silica reaches the action level. A lower-silica-content product can reduce the compliance burden during cutting and installation, making silica content an important specification field that many decorative masonry spec sheets do not address.
Recycled content and LEED certification fields
For LEED v4.1 and v5 projects, recycled content should be verified under ISO 14021 rather than simply declared by the manufacturer. When specifying breeze blocks for LEED projects, Jonite's engineered stone contains at least 30% verified recycled content, supporting LEED MR Credit 4. When reviewing a spec sheet, look for the ISO 14021 verification statement, the percentage of recycled content, and the manufacturer's USGBC membership. LEED v5 places greater emphasis on embodied carbon and product transparency, making independently verified sustainability information increasingly important during specification and product evaluation.
The independent testing gap — what to ask when values aren't certified
Not all performance values published on a breeze block spec sheet are independently tested. Some manufacturers rely on estimated material properties rather than certified test results, making it important to verify how the data was obtained. Look for recognised test standards, certification dates, and confirmation that testing was carried out by an independent laboratory. You should also ask whether a full test report is available on request. These questions help reduce specification risk and give greater confidence that the product will perform as expected once installed. This makes comparing architectural screen block specifications much more reliable than relying on estimated performance values alone.
Dimensional tolerance and how metric specs translate for US projects
Jonite's breeze blocks are specified in metric dimensions, including approximately 7.9 × 7.9 × 2.4 in (200 × 200 × 60mm) and 7.9 × 9.8 × 2.4 in (200 × 250 × 60mm), rather than US nominal sizing. For US projects, the submittal should include metric-to-imperial conversions together with installation guidance specifying uniform ¼–⅜ in (6–10mm) mortar joints. Within CSI Division 04 Part 2 (Products), dimensions, tolerances, and joint requirements should be clearly documented to avoid installation discrepancies. As a quality assurance measure, TMS 602 also recommends constructing a mock-up panel to verify alignment, joint consistency, and the finished appearance before installation begins.
Frequently asked questions
What is ASTM C140 and why does it matter for breeze block specifications?
ASTM C140 is the recognised US standard for testing decorative masonry units. ASTM C140 breeze block certification gives architects and specifiers confidence that compressive strength and water absorption have been independently tested using the appropriate US standard, making it easier to compare products using consistent performance criteria.
Can I use BS 476 Part 7 Class 1 as a fire rating on a US commercial project?
BS 476 Part 7 Class 1 is not a US code-compliance standard, but it provides recognised fire performance data by measuring surface spread of flame. On US projects, it should be included as supplementary performance information alongside the fire testing standard required by the project, such as ASTM E84 or NFPA 286.
What recycled content documentation does a LEED project need from a breeze block manufacturer?
For LEED projects, look for ISO 14021 verification of recycled content rather than manufacturer-declared claims. The spec sheet should identify the percentage of recycled content and confirm the manufacturer's USGBC membership where applicable. This provides the documentation needed to support LEED material credits.
Does silica content on a spec sheet affect my OSHA compliance obligations?
Yes. Crystalline silica content influences the level of OSHA compliance required under 29 CFR 1926.1153 during cutting and installation. Products with less than 1% crystalline silica, such as Jonite's engineered stone, can reduce the compliance burden compared with conventional concrete products that contain significantly higher silica levels.
How do I request a full submittal package from Jonite?
Contact Jonite through the trade inquiry page to request the latest technical submittal package. This includes current specifications, certifications, installation guidance, and supporting documentation to assist with product evaluation and project specification.
