What Is the ISO Construction Type for Concrete Block?
Concrete block walls are usually rated ISO Class 2, masonry construction, which often costs less to insure than wood frame.
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How the insurer classifies it
The underwriter looks at the exterior walls, not the frame inside or the roof. If the house has concrete block walls, it typically falls into the masonry class. The interior framing and roof structure don't change this rating, only the wall material does.
Why it affects your quote
Masonry walls resist fire spread better than wood frame, so insurers often price these homes lower for fire risk. This isn't guaranteed on every policy, since other factors like roof age, location and wind exposure also factor into what you're quoted before closing.
What your declarations page shows
Once your policy is issued, the construction type should appear on your declarations page or in the underwriting file. If you want to confirm the house was rated correctly, this is the document to check rather than guessing from the exterior.
What it doesn't cover
Masonry construction can lower fire risk pricing, but it has nothing to do with flood or earthquake coverage. Concrete block walls can still crack or shift in a quake, and a standard homeowners policy won't pay for flood damage regardless of what the walls are made of.
Construction type is only one piece of the quote
Masonry walls can mean lower fire pricing, but roof age, location, and wind exposure still shape what you pay. Comparing quotes before closing shows whether this house is priced the way it should be.
Does concrete block mean a lower wind or hurricane rate too
Masonry walls help with fire, but wind is a separate question. A hurricane or windstorm doesn't care what the walls are made of if the roof lifts off or a window breaks and lets pressure in. Insurers in wind-prone states look at the roof shape, the roof covering, the age of the roof, and whether the windows and doors are impact-rated or protected by shutters. A concrete block house with an old roof and unprotected windows can still carry a high wind premium.
Some states split the policy into two parts, one for wind and hail and one for everything else, especially along the coast. If that's the case where the house is, the construction type mentioned above applies mostly to the fire portion. The wind portion gets its own rating, sometimes from a separate insurer. The block walls may only count for a small credit rather than the main driver of price.
The declarations page will show this if it applies. Look for a wind or hurricane deductible listed separately from the main deductible, usually as a percentage of the dwelling coverage rather than a flat dollar amount. A windstorm mitigation form, if one is in the underwriting file, is where the roof age, roof shape, and opening protection get recorded. Asking whether that form was filled out and submitted is worth doing, since a missing form can mean paying for wind coverage without credit for features the house already has.
None of this changes what the walls are rated for fire. It just means the masonry classification answers one part of the quote and not the whole thing. A house can get full credit for concrete block construction and still be expensive to insure if the roof is older or the location sits in a high wind zone. The construction type by itself isn't a reliable signal of what the total premium will look like before closing.
Will concrete block cost less to insure than brick or stucco
Masonry covers more than one material, and insurers don't treat them all the same. Concrete block, brick veneer over wood frame, and stucco over frame can land in different classes depending on how the underwriter reads the exterior wall. Brick veneer is often just a facing over a wood frame structure. That can pull the rating back toward frame construction rather than true masonry. Stucco is applied over a base material, and that base, whether it's wood frame or block, is what the underwriter is actually rating.
Concrete block walls that are the structural wall, not a veneer over something else, are more likely to get the full masonry classification. The fire rating follows the load-bearing material, not the surface finish. If the exterior looks like stone or brick but the structure underneath is wood frame, the pricing can end up closer to a frame home than a reader would expect just from looking at the house.
Underwriters can describe the same house differently, so this is worth asking about directly when getting quotes. One insurer might classify a brick veneer home as frame construction. Another might give partial credit for the masonry veneer. There's no single rule that applies everywhere, and the state the house is in can affect which classification systems get used.
The construction type listed on the declarations page is the only way to know for certain how a given insurer rated the house. If the walls are solid concrete block, that should be stated plainly rather than described as brick, stone, or stucco. A mismatch between what the house is actually built from and what the policy says it's built from is worth raising before closing. It can affect both the price and whether a claim gets paid correctly later.
Before closing
Check that the declarations page names the actual wall material, concrete block, not brick or stucco. If it's wrong, ask the insurer to correct it before closing, since a mismatch can affect both price and a future claim.
