Historic Building and Masonry Restoration

Historic building cleaning is specialized, technical work that requires deep knowledge of preservation principles, materials, and methods. It cannot be approached like standard pressure washing.

The historic building opportunity

Why historic work is valuable:

• Specialized knowledge: Most contractors won’t touch historic buildings
• Premium pricing: Delicate work justifies higher rates
• Referral base: Historic preservation community is tight-knit
• Portfolio building: Photos of historic buildings make for strong marketing
• Repeat work: Historic buildings need regular maintenance
• Satisfaction: Preserving history is genuinely rewarding

Typical services:

• Building facades: $2,000-15,000 per building
• Masonry restoration cleaning: $3,000-20,000 per project
• Monuments and memorials: $500-3,000 each
• Historic structures: Bridges, towers, follies
• Consultation: $200-500 per hour for preservation advice

Understanding historic buildings

Why historic buildings are different:

Historic buildings were built with different materials, techniques, and purposes. They’ve survived decades or centuries of weathering. They cannot be replaced.

Common historic materials:

• Brick: Soft, handmade bricks from 1800s are much softer than modern brick
• Sandstone/limestone: Sedimentary stone, relatively soft, absorbs water
• Granite/marble: Harder but can be damaged by acids and abrasives
• Terracotta: Glazed clay architectural elements, extremely delicate
• Cast stone: Concrete made to resemble stone, can deteriorate
• Stucco: Historic lime-based stucco is different from modern cement stucco
• Wood: Historic woodwork requires special care

Deterioration mechanisms:

• Moisture penetration: Historic materials absorb and release moisture
• Salt crystallization: Salt from pollution or deicing salts expands inside masonry, causing spalling
• Biological growth: Moss, lichen, algae accelerate deterioration
• Atmospheric pollution: Creates acid stains and crusts
• Freeze-thaw cycles: Water expands when freezing, cracking masonry
• Inappropriate previous repairs: Hard mortars, sealants, incompatible materials

Cleaning can accelerate deterioration if done wrong.

The preservation approach

Historic preservation follows principles:

1. Do no harm: The building has survived this long. Don’t shorten its life.
2. Gentlest effective means: Use the least aggressive method that works.
3. Test first: Always test in inconspicuous areas before full cleaning.
4. Document: Photograph before, during, after.
5. Preserve patina: Aged appearance is part of historic character.
6. Know when to stop: Some stains are preferable to damage.

Secretary of the Interior’s Standards:

For officially designated historic buildings, cleaning must follow these standards:

• Identify, retain, and preserve historic features
• Protect and maintain historic materials
• Repair rather than replace when possible
• Use treatments that are reversible if possible

Equipment and methods for historic buildings

Pressure is the enemy of historic masonry.

Recommended equipment:

• Low pressure: 1,000-1,500 PSI maximum for most historic masonry
• High flow: 4-6 GPM to compensate for low pressure
• Chemical application: Downstream injector for even coverage
• Soft wash systems: For very delicate surfaces
• Variable pressure: Essential so you can dial pressure down
• Multiple nozzle tips: 40-degree (white) and 65-degree (black) for delicate work

Avoid:

• High pressure: Anything over 2,000 PSI risks damage
• Surface cleaners: Can be too aggressive, concentrate pressure
• Turbo nozzles: Never appropriate for historic masonry
• Hot water: Can accelerate salt damage, use cautiously
• Abrasive methods: Sandblasting destroys historic masonry—never use

Chemical considerations

Chemical choice is critical for historic buildings.

Appropriate chemicals:

• Purpose-formulated cleaners: Historic masonry cleaners (D/2, EnviroKlean, etc.)
• pH-neutral cleaners: For general cleaning
• Biocides: For organic growth (moss, lichen, algae)
• Poultices: For deep stain extraction

Chemicals to avoid:

• Muriatic acid (HCl): Too aggressive, causes salt damage
• Bleach (sodium hypochlorite): Can damage masonry, leave salt deposits
• Harsh degreasers: Too aggressive for historic materials
• Unknown products: Only use products with proven track record on historic masonry

Always:

• Read SDS before using any chemical
• Test first in inconspicuous area
• Rinse thoroughly to remove all chemical residue
• Neutralize if using acidic or alkaline products

Cleaning techniques by material

Historic brick

Characteristics: Soft, porous, often painted or covered in soot from coal-era heating.

Method:

1. Test first: Always. Paint may be intentional.
2. Pre-wet: Saturate brick to reduce chemical absorption.
3. Apply cleaner: pH-neutral or purpose-formulated brick cleaner.
4. Gentle agitation: Soft brush if needed.
5. Low-pressure rinse: 1,000-1,500 PSI, white tip, 12+ inches from surface.
6. Thorough rinse: Multiple low-pressure passes.

Never: Blast with high pressure, use harsh acids, remove intentional paint.

Sandstone and limestone

Characteristics: Sedimentary stone, very soft, absorbs water readily.

Method:

1. Pre-wet thoroughly: Saturate completely to reduce chemical penetration.
2. Apply cleaner: Purpose-formulated stone cleaner.
3. Extended dwell: 15-30 minutes—stone absorbs slowly.
4. Gentle agitation: Soft natural-bristle brush.
5. Very low-pressure rinse: 800-1,200 PSI, white tip, keep distance.
6. Multiple gentle rinses: Stone holds chemicals in pores.

Special considerations:

• Never let cleaners dry on stone—causes staining
• Protect carved elements with extra care
• Work small sections you can manage before cleaners dry

Granite and marble

Characteristics: Harder but can be damaged by acids and abrasives.

Method:

1. Test for sealers: Some historic granite has been sealed.
2. Apply cleaner: pH-neutral or slightly alkaline.
3. Moderate dwell: 10-15 minutes.
4. Low-pressure rinse: 1,200-1,500 PSI.
5. Inspect: May require multiple gentle treatments.

Never: Use acidic cleaners on marble or calcareous stones.

Terracotta

Characteristics: Glazed clay, extremely delicate, glaze can be damaged.

Method:

1. Extreme caution: This is among the most delicate historic materials.
2. Hand-clean often: Soft cloth, mild detergent, low-pressure rinse.
3. Test absolutely everything: Glaze varies widely.
4. Consider professional: For significant terracotta, hire specialist.

Never: Blast terracotta with anything. Most pressure washing is too aggressive.

Historic stucco

Characteristics: Lime-based, soft, permeable, different from modern cement stucco.

Method:

1. Identify type: Lime vs. cement stucco (test if unsure)
2. Gentle cleaner: Purpose-formulated stucco cleaner or pH-neutral.
3. Soft wash method: Chemical cleaning with minimal pressure.
4. Very low pressure: 800-1,000 PSI maximum.
5. Careful around repairs: Historic patches may be incompatible

Wood features

Characteristics: Historic woodwork is often irreplaceable.

Method:

1. Identify wood species: Affects approach
2. Soft wash preferred: Chemical cleaning over pressure
3. Very low pressure: If any pressure at all
4. Protect: Don’t blast paint if intentional
5. Consider specialist: For significant historic woodwork

Common historic building stains

Carbonaceous crusts: Black soot from industrial era, common on urban historic buildings.

• Cleaning: Specialized carbon removal cleaners, low pressure, multiple treatments

Organic growth: Moss, lichen, algae accelerate masonry decay.

• Cleaning: Biocides, gentle mechanical removal, low-pressure rinse

Iron staining: From architectural metal features, ties, anchors.

• Cleaning: Purpose-formulated rust removers, test first

Efflorescence: White salt deposits, indicates moisture problems.

• Cleaning: Dry brush first, then very gentle low-pressure rinse. Address moisture source.

Paint: May be historic or applied later. Test to determine.

• If paint is historic: Do not remove
• If paint is not historic: May remove with appropriate paint strippers (test first)

The restoration process

Phase 1: Assessment

1. Document existing conditions: Extensive photography
2. Identify materials: Brick type, stone type, mortar composition
3. Test cleaning methods: In multiple inconspicuous areas
4. Determine appropriate approach: Based on testing results
5. Develop plan: Specific methods for each material and condition

Phase 2: Preparation

1. Protect features: Cover windows, doors, architectural elements
2. Protect landscaping: Plants, soil, hardscape
3. Contain runoff: Historic buildings often have no storm drains
4. Set up equipment: Low pressure, appropriate chemicals

Phase 3: Cleaning

1. Work in sections: Manageable areas you can complete before cleaners dry
2. Test frequently: Conditions change across building
3. Document progress: Photos during cleaning
4. Adjust as needed: What works in one area may not work in another
5. Patience: Historic building cleaning cannot be rushed

Phase 4: Final Steps

1. Final inspection: Close inspection of entire facade
2. Touch-up work: Address missed spots or problem areas
3. Neutralization: If acidic or alkaline products used
4. Final documentation: Complete photo record
5. Preservation report: Document methods used for future reference

Pricing historic work

Historic building work is not comparable to standard pressure washing.

Pricing factors:

• Testing required: Bill for testing time
• Specialized equipment: Low-pressure systems, specific chemicals
• Slower work rate: Historic work cannot be rushed
• Expertise required: Premium for specialized knowledge
• Liability exposure: Higher risk working on irreplaceable buildings
• Documentation time: Photos, reports, preservation compliance

Pricing methods:

Time and materials: Most common for historic work. $150-300/hour depending on complexity.

Per square foot: $2-10 per square foot depending on material and condition. Much higher than standard work.

Project pricing: Lump sum for entire building or facade, based on detailed assessment.

Example pricing:

Small historic building (3,000 sq ft brick facade):

• Assessment and testing: $800
• Cleaning: 3,000 sq ft × $4 = $12,000
• Documentation: $400
• Total: ~$13,200

Large historic courthouse (15,000 sq ft sandstone):

• Assessment: $2,000
• Testing: $1,500
• Cleaning: 15,000 sq ft × $6 = $90,000
• Documentation and report: $2,000
• Total: ~$95,500

Working with preservation organizations

Historic preservation community is tight-knit. Build relationships.

Key organizations:

• Local historical societies: Often own or advocate for historic buildings
• Preservation commissions: Review and approve work on designated historic buildings
• State historic preservation offices (SHPO): Oversee historic resources
• National Trust for Historic Preservation: Advocacy and resources
• Local preservation nonprofits: Advocate for specific buildings or districts

Building relationships:

• Attend preservation events: Conferences, workshops, tours
• Join preservation organizations: Become known in the community
• Work with preservation professionals: Architects, conservators, historians
• Educate yourself: Take courses in historic preservation
• Volunteer: Demonstrate commitment to preservation

Common mistakes to avoid

Using too much pressure: Most common error. Historic masonry cannot handle high pressure.

Wrong chemicals: Using standard pressure washing chemicals on historic materials causes damage.

Not testing: Assuming methods work without testing leads to damage.

Rushing: Historic work takes time. Trying to go faster damages buildings.

Removing intentional features: “Cleaning” paint, coatings, or patina that are actually historic character.

Ignoring professional advice: Preservation consultants know what they’re talking about. Listen to them.

Working on designated buildings without approval: Many historic buildings have legal protection. Unauthorized work can have serious consequences.

Safety and liability

Historic building work has unique risks:

• Working at height: Historic buildings often have tall facades, towers, spires
• Fragile materials: Loose masonry, deteriorated features can fall
• Unknown conditions: Hidden deterioration, previous repairs
• Public access: Many historic buildings are in public areas
• Irreplaceable architecture: Damage cannot be easily fixed

Insurance:

• Higher liability limits: $2-5 million for historic work
• Professional liability: Errors and omissions coverage
• Workers compensation: If you have employees

Legal considerations:

• Historic designation: Local, state, or national designation creates legal requirements
• Preservation easements: Legal restrictions on changes
• Certificate of appropriateness: Required before work on designated buildings

The bottom line

The barriers to entry (knowledge, testing, patience, specialized equipment) protect you from competition. Most contractors won’t or can’t do this work.

The rewards are real: premium pricing, strong portfolio pieces, referrals within the preservation community, and the satisfaction of keeping irreplaceable buildings standing.

Start small. Learn preservation principles. Test everything. Work with preservation professionals. Build your reputation slowly. Historic building work is some of the most rewarding and profitable work in the trade, but only if you respect the buildings and do it right.

The buildings are the priority. You’re a temporary caretaker.