Asbestos Brick Siding
Asbestos brick siding—widely known by historical trade names such as Insulbrick or asphalt faux-brick siding—was an extremely popular exterior cladding product installed on residential bungalows and commercial outbuildings between the 1930s and 1960s. Composed of thick asphalt-saturated wood-fiber board surfaced with mineral granules patterned to mimic kiln-fired red brick, these composite panels incorporated chrysotile asbestos to achieve weatherproofing and fire resistance.
The History and Construction of Asphalt Faux-Brick Panels
During the Great Depression and post-war housing boom, homeowners sought affordable, durable exterior siding that provided thermal insulation and eliminated the need for periodic exterior painting. Manufacturers met this demand by producing rigid, tongue-and-groove siding panels marketed as insulated brick siding.
The manufacturing process involved saturating heavy wood-fiber core boards with petroleum asphalt. The exterior face was coated in a dense asphaltic mastic blended with chrysotile asbestos fibers (typically ten to twenty-five percent) and embedded with colored ceramic stone granules to simulate brickwork and mortar lines.
| Panel Layer | Material Composition | Average Asbestos Content | Structural Function |
|---|---|---|---|
| Exterior Granular Face | Colored crushed stone granules in asphalt mastic | 10% to 20% Chrysotile asbestos | Weather barrier mimicking kiln-fired brick and mortar |
| Adhesive Mastic Layer | Petroleum bitumen, asbestos fiber binder | 15% to 30% Chrysotile asbestos | Binds stone granules securely to the insulation core |
| Insulating Fiberboard Core | Asphalt-saturated wood pulp / bagasse fiber | Zero to Trace (Rarely contains mineral fibers) | Thermal insulation and structural rigidity |
| Backing Weather Barrier | Bitumen-impregnated organic paper felt | 5% to 15% Chrysotile asbestos | Resists moisture intrusion against wood wall sheathing |
Weathering Degradation, Fire Hazards, and Health Risks
While intact asbestos brick siding is classified under EPA regulations as Category I Non-Friable ACM, decades of direct sun exposure, rain, and freeze-thaw cycles degrade the petroleum asphalt binder. Over time, the surface mastic dries out, cracks, and delaminates, shedding mineral granules and exposing raw, friable asbestos fibers.
Furthermore, because the underlying core board consists of asphalt-soaked cellulose, Insulbrick panels present significant fire hazards. If ignited by external flames or electrical shorts, the asphalt core burns with intense heat and thick black smoke. Attempting to tear off weathered panels dry with crowbars shatters the brittle boards, releasing clouds of respirable dust.
| Remodeling / Removal Method | Physical Hazard Dynamic | Airborne Exposure Level | Approved Regulatory Action |
|---|---|---|---|
| Dry Mechanical Tearing | Snaps brittle fiberboards into powdery rubble | Severe (Distributes dust clouds around yard) | Prohibited under EPA NESHAP rules |
| High-Pressure Power Washing | Blasts asphalt binder into toxic airborne slurry | High (Severe soil and downspout contamination) | Strictly Prohibited on weathered siding |
| Vinyl Siding Encapsulation | Caps panels beneath fanfold foam and vinyl | Zero (Safe, permanent encapsulation) | Approved and recommended method |
| Controlled Manual Wet Abatement | Mists panels with water; unfastens nails whole | Low to Minimal (Wet methods bind fibers) | Use surfactant misting and P100 respirators |
When updating a home with vintage asbestos brick siding, encapsulation is almost always the preferred, cost-effective solution. Installing contoured fanfold foam board directly over the faux-brick panels and hanging new vinyl or fiber-cement siding seals the asbestos permanently while significantly improving wall insulation.
However, if panels are severely water-rotted, buckling, or infested with pests, licensed abatement contractors must remove the boards manually under continuous surfactant misting, wrapping bundles in 6-mil poly for manifested disposal at a certified landfill.
How to Safely Address Asbestos Brick Siding
Step-by-step procedure for inspecting, encapsulating, or abating asphalt-asbestos brick siding.
Inspect Panel Condition and Fasteners
Examine exterior walls to verify if siding is Insulbrick (asphalt faux-brick texture) and check for areas of buckling, water rot, or missing granules.
Confirm Asbestos Content with Lab Testing
Extract a small corner fragment while wearing a P100 respirator, misting with water, and submit it to an NVLAP lab for PLM analysis.
Select Encapsulation over Demolition
If panels are flat and adhered, install 1/2-inch fanfold foam board directly over the brick siding to encapsulate fibers safely and add insulation.
Perform Manual Wet Removal if Demolishing
If removal is required, saturate panels with surfactant water, gently pull nails with a cat's paw tool, and lower whole panels without snapping them.
Double-Wrap Waste in 6-Mil Poly Sheeting
Stack panels on wooden pallets, wrap bundles hermetically in double-layer 6-mil plastic with OSHA warning labels, and manifest for certified landfill burial.
Frequently Asked Questions (7 Questions Answered)
Q1: What is Insulbrick siding?
Insulbrick is a vintage asphalt-fiberboard siding panel surfaced with stone granules to mimic red brick, manufactured from the 1930s to 1960s.
Q2: Does faux-brick asphalt siding always contain asbestos?
Most asphalt brick siding made prior to 1975 contains 10% to 25% chrysotile asbestos in the exterior mastic binder.
Q3: Can I install vinyl siding over asbestos brick siding?
Yes, installing fanfold foam backing and vinyl siding directly over intact brick siding is an approved, safe encapsulation method.
Q4: Is asbestos brick siding dangerous if left alone?
If the panels are intact, painted, and not shedding dust, they present minimal risk because the fibers are bound in asphalt.
Q5: Can I pressure wash my old asbestos brick siding?
Never pressure wash asbestos siding; the high-pressure water stream erodes the asphalt binder and blasts toxic fibers across your property.
Q6: Is Insulbrick siding a fire hazard?
Yes, the thick asphalt-soaked fiberboard core burns rapidly with intense black smoke if ignited by exterior flames.
Q7: How much does it cost to remove asbestos brick siding?
Professional removal typically costs between $6 and $14 per square foot, including containment, manual unfastening, and hazardous disposal.
Final Thoughts & Key Takeaways
Asbestos brick siding represents a fascinating chapter in mid-century building materials that demands respectful handling today. Never pressure wash or dry-rip aging Insulbrick panels. By choosing safe encapsulation with modern vinyl cladding or retaining certified abatement contractors for wet manual removal, homeowners can modernize their exterior safely and sustainably.