Have you ever seen a brick building and assumed it must be masonry construction? That quick judgment can be misleading. Joisted masonry vs frame is really about how a building is built, not just how it looks.
In this guide, I’ll explain the difference in plain English. You’ll see how wall, floor, roof, and framing materials affect the construction class and fire-resistance rating.
I’ll also compare fire resistance, cost, durability, common uses, and insurance considerations. Most importantly, I’ll show you how to identify the construction type when the exterior does not tell the whole story.
If you need to classify an existing building, these points can help you know what to check before making a decision.
What Is Joisted Masonry?
Joisted masonry is a building type with masonry exterior walls and combustible floor or roof systems, often using wood joists.
The term sounds more technical than it is. Think of a building where the outside load-bearing walls are made from masonry, but the floors or roof contain wood joists.
The masonry walls provide a strong exterior enclosure, while the combustible members inside still affect the building's fire risk. The fire-resistance rating also depends on the materials and assemblies used throughout the structure.
This construction is common in older commercial buildings and some low-rise structures. The exact materials can vary from one building to another, so you should not classify a property from its appearance alone. Plans, permits, construction records, or an inspection can provide a more reliable answer.
What Is Frame?
Frame construction uses a combustible structural frame, commonly wood, to support major parts of the building.
In many frame buildings, wood studs, beams, joists, rafters, or related components form the main structural system. The exterior can use siding, brick veneer, stucco, or other finishes, so the building does not have to look like a traditional wood house.
This is why exterior appearance can cause confusion when you are trying to identify a construction class. Frame buildings are common in residential construction because wood framing can be practical, flexible, and relatively quick to assemble.
Fire protection depends on the full assembly, including wall construction, floor and roof systems, fire stops, and other protective measures. US Assure notes that adding non-combustible exterior materials such as masonry veneer does not by itself change a frame classification.
Joisted Masonry vs Frame: Construction Classifications
The key distinction is that Frame is ISO Class 1, while Joisted Masonry is ISO Class 2.
Frame Construction: ISO Class 1
ISO Class 1 refers to frame construction, where combustible structural materials form a major part of the building system.
Wood framing is a common example. Studs, joists, rafters, beams, and other combustible members can carry loads or form major parts of the structure. This does not mean every frame building has the same fire performance.
Fire-rated assemblies, sprinklers, gypsum products, fire stops, and other measures can reduce risk. Still, the presence of substantial combustible structural material gives Class 1 buildings a different fire-risk profile from buildings that use masonry exterior load-bearing walls. A brick veneer over wood framing can also remain Class 1 because the veneer does not change the underlying structural system.
Joisted Masonry: ISO Class 2
ISO Class 2 refers to joisted masonry construction, where masonry exterior walls are combined with combustible floor or roof systems.
The exterior load-bearing walls may use brick, concrete block, stone, or similar masonry. Inside the building, wood joists or other combustible members may support floors and roofs.
This combination gives the building more substantial masonry protection than typical frame construction, but it does not make the entire structure non-combustible. The combustible floor and roof components still matter during a fire.
That is why joisted masonry sits between frame construction and Non-Combustible Class 3 in the six-class system. The actual materials and assemblies should still be checked before assigning a classification.
Where They Fit in the Six Construction Classes
The six broad construction classes provide context for where Frame and Joisted Masonry sit within the larger classification system.
- Frame: Class 1, with substantial combustible structural components.
- Joisted Masonry: Class 2, with masonry exterior walls and combustible floor or roof systems.
- Non-Combustible: Class 3, using materials that do not readily contribute fuel to a fire.
- Masonry Non-Combustible: Class 4, combining masonry with non-combustible structural elements.
- Modified Fire-Resistive: Class 5, designed with greater fire resistance than the lower classes.
- Fire-Resistive: Class 6, providing the highest level of fire resistance in this classification framework.
These classes help insurers and other professionals describe construction characteristics. The ISO construction classification considers building elements such as walls, floors, roofs, and structural frames, along with fire resistance. Exact classification should be confirmed from the applicable classification rules and building information.
Joisted Masonry vs Frame: Side-by-Side Comparison
This comparison shows how the two construction types differ in structure, fire exposure, cost, and common use.
| Factor | Joisted Masonry | Frame |
| ISO classification | Class 2 | Class 1 |
| Exterior walls | Masonry | Typically combustible framing |
| Floor system | Often wood/combustible | Usually wood/combustible |
| Roof system | Often wood/combustible | Usually wood/combustible |
| Fire resistance | Generally better exterior resistance | Greater combustible exposure |
| Construction speed | Moderate | Generally faster |
| Initial cost | Moderate | Often lower |
| Durability | Durable masonry exterior | Depends heavily on framing and protection |
| Common uses | Small commercial buildings, retail, offices | Homes and small commercial buildings |
The right classification depends on the actual structural materials, load-bearing walls, floor and roof systems, and their fire characteristics, not the finish you see from the street.
What Materials Determine the Construction Classification?
Look at the building's structural components rather than judging it by its exterior finish.
The main factors include:
- Structural frame: Check what carries the building's main loads.
- Exterior load-bearing walls: Determine if they use masonry or combustible framing.
- Interior load-bearing elements: Check columns, walls, beams, and other supporting members.
- Floors: Identify the materials supporting each floor.
- Roof: Check the structural roof system and its materials.
- Combustibility and fire-resistance ratings: Review how the materials perform under fire conditions.
A key example is a building with brick or stone veneer over wood framing. It may look like masonry construction from the outside, but the underlying wood frame can still place it in the frame category. When classification matters for insurance, code work, or property records, I would verify the structural system rather than rely on appearance. These checks also match the main building elements insurers use when determining construction type.
Fire Resistance and Safety Differences
Joisted masonry generally has less combustible exposure at its exterior walls, but its wood floors and roof can still contribute to fire spread.
The difference comes down to the materials used throughout the building. Masonry exterior walls can provide an advantage because brick, concrete block, and similar materials do not burn like wood framing.
However, joisted masonry is not fireproof. Combustible joists, roof members, and floor systems can still burn and may allow fire to move through parts of the structure.
Frame construction generally contains more combustible structural material. That can increase fire exposure when compared with joisted masonry.
Protection measures such as automatic sprinklers, fire-rated assemblies, fire stops, and properly installed protective materials can improve fire performance.
Still, actual results depend on the complete building assembly and its fire-resistance rating. The requirements that apply can also vary by project and local code.
Advantages and Limitations of Joisted Masonry vs Frame
Both types can work well, but they suit different construction needs, budgets, and building conditions.
Joisted Masonry
Joisted masonry can be a practical choice when a durable masonry exterior and lower exterior fire exposure matter.
Advantages
- Durable masonry exterior
- Generally better exterior fire resistance than typical frame construction
- Good thermal and acoustic performance
- Practical for many low- to mid-rise buildings
Limitations
- Combustible floor and roof components remain a fire concern
- Masonry work can require more labor
- Wood joists can be affected by moisture and pests
- Seismic performance depends on proper design and connections
The main point is that masonry does not remove every structural risk. The complete building system still matters.
Frame Construction
Frame construction can make sense when faster construction, flexible layouts, and lower initial costs are important.
Advantages
- Generally faster to build
- Often lower initial construction costs
- Flexible design
- Easy utility installation
Limitations
- Greater combustible-material exposure
- Vulnerability to moisture, rot, and insects
- Requires careful fire-protection detailing
- Masonry veneer does not automatically change its classification
Frame construction is not automatically a poor choice. Its performance depends on the materials, design, workmanship, maintenance, and protective systems used in the building.
Where Are Joisted Masonry and Frame Buildings Used?
Joisted masonry often appears in low- to mid-rise commercial buildings, while frame construction is common in homes and smaller commercial projects.
Joisted masonry may be found in retail buildings, restaurants, offices, warehouses, schools, and similar structures where masonry exterior walls are combined with combustible floor or roof systems.
Frame construction is common in single-family homes, residential buildings, and small commercial structures, especially when speed and flexible layouts matter. Dixon also lists retail stores, restaurants, offices, schools, churches, and light industrial facilities as examples of joisted masonry use.
Actual applications vary. Occupancy, local building codes, structural requirements, climate, project design, and budget all affect the choice. If you are checking an existing property, do not assume its construction class from its age or appearance. Two buildings that look similar from outside can use very different structural systems.
How Construction Type Affects Insurance
Construction classification can affect insurance because insurers use building materials and fire exposure when assessing property risk.
A Class 1 frame building generally has more combustible structural material than a Class 2 joisted masonry building. That difference can affect underwriting and may influence the premium. For construction projects, builders risk insurance can also consider the construction type when assessing risk and coverage needs. US Assure notes that building elements and fire-resistance ratings can influence builders risk premium costs.
Insurers can also consider.
- Location
- Building occupancy
- Fire protection systems
- Sprinklers
- Claims history
- Building condition
- Electrical and heating systems
- Local fire protection resources
This is why I would not assume that a joisted masonry building will always have a lower premium than a frame building. Accurate classification matters, but the final insurance cost depends on the property's full risk profile and the insurer's underwriting rules.
Joisted Masonry vs Frame: Which Is Better?
There is no single winner. The better choice depends on what you need from the building and which risks matter most to you.
Joisted masonry may be a better fit when you value a durable masonry exterior and lower combustible exposure at the exterior walls. Frame construction may work better when speed, flexibility, and lower initial cost are higher priorities.
Before choosing, consider:
- Climate and weather exposure
- Building occupancy
- Local building codes
- Construction budget
- Long-term maintenance
- Fire protection
- Expected building use
For an existing property, I would verify the actual construction classification before making a decision. If the records are unclear, a structural engineer or qualified building professional can help determine whether the masonry is structural or simply veneer. A brick exterior alone does not tell you enough.
How to Identify Whether a Building Is Joisted Masonry or Frame
Start with the structural system, then confirm the information through reliable building records or a qualified professional.
- Identify the exterior wall material.Check if the load-bearing exterior walls are masonry or combustible framing.
- Determine how the floors are constructed.Look for wood joists, concrete, steel, or other floor-support systems.
- Check the roof construction.Identify the material and structural members supporting the roof.
- Identify the structural framing material.Determine what carries the building's main loads.
- Review plans, permits, or construction documents.These records can provide information that is not visible from outside.
- Consult a qualified professional if the classification is unclear.An experienced inspector, engineer, contractor, or other qualified professional can help confirm the construction type.
Key takeaway: Do not classify a building only because its exterior looks like brick or masonry. The materials behind the finish and throughout the structural system matter.
Conclusion
If you are comparing joisted masonry vs frame, the biggest lesson is simple: look at how the building is actually constructed, not just how it looks.
Joisted masonry combines masonry exterior walls with combustible floor or roof systems, while frame construction relies more heavily on combustible framing.
I would always check the plans, permits, and structural details before making a classification decision. That small step can prevent costly assumptions later.
Have you checked a building and found that its appearance did not match its construction type? Share your experience in the comments, or check our other construction guides for more practical explanations.
Frequently Asked Questions
Can a brick building still be classified as frame construction?
Yes, a brick building can still be frame construction if the brick is only veneer over a wood or other combustible structural frame.
Is joisted masonry safer than frame construction in a fire?
Generally, joisted masonry has less combustible exterior exposure, but its wood joists, floors, and roof can still contribute to fire spread.
Can a building change from frame to joisted masonry after renovation?
Yes, major structural changes can affect its classification, but the final classification depends on the completed building system and applicable classification rules.
Does joisted masonry cost more to insure than frame construction?
Not always, because insurance costs also depend on location, occupancy, protection systems, claims history, building condition, and other risk factors.
