10 min read · Siding Replacement
If your older home's 'brick' walls give slightly when pressed and show seams like a shingle, you're probably looking at asphalt sheet siding — the faux-brick and faux-stone cladding sold from the 1930s into the 1960s under names like Inselbric (the spelling varies; most people say 'Insulbrick'). It was an inexpensive renovation skin for its era, and most of it is now decades past its useful life. This guide covers how to identify it, why it fails, the asbestos caution that governs how it comes off the wall, and the occasional good news hiding underneath: original wood siding that's sometimes restorable.
What Insulbrick-type asphalt siding is
Asphalt siding is a close cousin of the asphalt roof shingle: colored mineral granules bonded with asphalt to a fiberboard or felt base — InspectAPedia describes 'colored mineral granules bonded to an organic or wood-product base with asphalt,' sometimes laminated to a softer wood-based insulating board panel. Manufacturers embossed the sheets to imitate brick, stone, and shingles, and sold them under a crowd of trade names — the Mastic Corporation's InselBric (from 1932), InselStone, and Sears' catalog lines among them. From the 1930s through the 1950s it boomed as a renovation product: a cheap, 'modern,' low-upkeep skin nailed over tired wood walls, often with an insulating-board backer that gave walls a slightly padded feel. By the 1960s, as InspectAPedia puts it, aluminum siding 'pretty-much ended' the asphalt siding industry. In California you'll find it on pre-war bungalows and farmhouses, detached garages, and rural outbuildings — anywhere a mid-century budget re-clad happened and nothing has happened since.
How to identify it
The tells are consistent. **It reads as brick or stone but behaves like a shingle:** granule-textured surface that sheds gritty sand like an old roof shingle, visible sheet seams and nail heads on a wall pretending to be masonry, and mortar 'joints' that are printed or embossed rather than recessed real mortar. **It's soft:** press it and it gives slightly — real brick doesn't — and a gentle knuckle tap sounds dull and papery rather than solid. **Its edges tell the story:** at corners, windows, and damaged spots you can often see the fiberboard or felt core in cross-section, sometimes with a dark asphalt layer. **Context helps:** a 1920s–40s house form wearing 'brick' that wraps like wallpaper is almost never brick. Identification matters because the maintenance and replacement logic is nothing like masonry's — and because of what the next section covers, resist the urge to break a piece off to check. Look, press gently, photograph — don't cut or snap samples yourself.
Why it fails
Age is unkind to asphalt sheet siding in specific ways. The asphalt binder embrittles over decades — accelerated by California sun — so sheets that were once flexible now **crack, split, and shatter at impacts**, and every crack is permanent (there's no refinishing a granule-faced sheet). The fiberboard core is the deeper problem: once water finds an opening, the **wood-based board absorbs and holds moisture**, swelling, delaminating, and feeding rot in the sheathing and framing behind it — and a rain-screen it is not. InspectAPedia's general warning applies with force here: 'once openings appear in any building siding material the deterioration of the building accelerates.' Add **granule loss** (bald, chalky patches that age the wall by decades), **buckling** where sheets have absorbed moisture or fasteners have let go, and **pest harborage** — the soft, warm gap between the old wall and the sheet is agreeable real estate for insects and rodents. A wall of 70-year-old asphalt siding isn't a maintenance candidate; it's a replacement candidate. The honest question is only about what's underneath and how the removal is handled.
The asbestos caution — test before anyone cuts or demos
Here is the part that governs the whole project: **some asphalt siding products and their felt or fiberboard backers contained asbestos** — InspectAPedia's asphalt-siding asbestos FAQs note that 'some asphalt-impregnated (paper-based) siding materials contain asbestos,' including the backer, and the asphalt-felt underlayment papers of the era are suspect too. And per the EPA, you cannot tell whether a material contains asbestos by looking at it. So the rule mirrors the one in our asbestos (transite) siding guide: treat the material as suspect until lab testing says otherwise. Don't cut it, sand it, grind it, saw it, pressure-wash it, or tear it off to 'see what's under there' — intact material generally keeps its fibers bound, and disturbance is precisely the hazard. The sane sequence is sampling and testing by an accredited professional before demolition is planned. If the test is positive, removal and disposal follow California's regulated-abatement path, exactly as with transite; if it's negative, tear-off proceeds as ordinary (careful) demolition. Testing costs little; skipping it can cost a great deal.
What replacement looks like — and the wood siding sometimes underneath
Once testing has cleared the path, replacement follows the standard good-practice arc: full tear-off of the sheets and backer boards, a real **sheathing and framing assessment** (expect localized rot repairs where the fiberboard held water), a continuous **weather-resistive barrier** with integrated flashing at every opening — the layer these walls never properly had — and new cladding; for most homes, non-combustible fiber cement in a lap or shingle profile appropriate to the house's era, as covered in our old-siding replacement guide. But check for the occasional gift first: because asphalt sheet siding was a **renovation product nailed over existing walls**, many pre-war homes still have their original wood siding underneath. Sometimes it emerges nail-riddled and weathered beyond saving; sometimes — more often than you'd guess — it's restorable, and a bungalow gets its original clapboard or shiplap face back with repairs, prep, and paint. We look before we spec. It's the difference between a re-side and, occasionally, a restoration.
Key takeaways
- Insulbrick-type asphalt siding is granule-faced, asphalt-bound sheet material on a fiberboard/felt core, embossed as faux brick or stone — sold from the 1930s until aluminum ended the category in the 1960s.
- Identify it by feel and detail: it gives under pressure, sheds granules, shows sheet seams and printed 'mortar' joints — but don't cut or snap a sample to check.
- It fails by embrittlement (cracking, shattering), moisture-holding fiberboard (hidden rot), granule loss, buckling, and pest harborage — and none of it is repairable in any lasting way.
- Some asphalt siding and its backers contained asbestos, and you can't tell by looking: lab-test before any cutting or demolition, and route positive results through regulated abatement — same framework as transite siding.
- Replacement is tear-off, rot repair, a real WRB, and fiber cement — but check underneath first: original wood siding often survives under the sheets, and is sometimes restorable.
FAQ
Quick Answers
Some does, some doesn't — and that's the problem. Sources documenting these products note that some asphalt-impregnated siding materials contain asbestos, including in the fiberboard or felt backer, and the EPA is explicit that you can't identify asbestos by sight. The only responsible answer for your specific wall is lab testing of a professionally collected sample before any cutting or demolition. Until then, treat it as suspect and leave it undisturbed.
It's occasionally done, but we don't recommend it. Covering the sheets traps a moisture-holding fiberboard layer (and any rot it's feeding) inside your new wall, gives fasteners a mushy substrate, and skips the sheathing assessment and weather-resistive barrier that make a re-side durable. If the material tests positive for asbestos, encapsulation-versus-removal becomes a conversation with abatement professionals about your specific situation — but as a general building practice, tear-off with a clean substrate is the better wall.
Quite possibly. Asphalt sheet siding was overwhelmingly a renovation product, nailed over the walls a house already had — so pre-war homes often still carry their original clapboard, shiplap, or drop siding underneath. Condition varies from restorable to hopeless: the overlay's nail pattern, trapped moisture, and decades of concealment all take a toll. We assess what's under there (after asbestos testing clears the way) before speccing replacement, because restoring an original wood face is sometimes the better project.
Honestly: nothing in the sheet-siding category — and that's fine, because the granule-faced brick imitation is what dates these walls. If you want masonry character, real brick or stone veneer over a properly detailed backup is a genuine (and costlier) path — see our brick and stone veneer guides. Most owners instead choose a lap or shingle profile in fiber cement suited to the home's era, which restores the house to something closer to its original architecture than the 1950s overlay ever was.
Sources
Authoritative references
- InspectAPedia — Asphalt siding (Insulbrick-type) history, patterns, inspection & repair
- InspectAPedia — Asphalt siding asbestos FAQs (some products & felt backers contain asbestos)
- U.S. EPA — Learn About Asbestos (asbestos-containing materials in homes)
- U.S. EPA — Protect Your Family from Exposures to Asbestos
External links to government, code, and manufacturer sources. Sierra Siding is not affiliated with these organizations; references are provided for verification.