More Detail: Building Envelope and Roofing Systems

Building Envelope Systems for Existing Mid-Rise Office Buildings in North Texas

The building envelope—roofing, façades, windows, sealants, and waterproofing systems—protects a mid-rise office building from North Texas’ extreme climate conditions. With frequent hailstorms, intense UV exposure, high winds, heavy rains, and occasional freezes, envelope systems degrade faster here than in many parts of the country. Existing mid-rise buildings (4–12 stories) often require comprehensive repairs, replacements, or modern upgrades to maintain performance and prevent water intrusion.

This page provides detailed descriptions of all major roofing systems, façade systems, envelope components, and waterproofing assemblies found in North Texas commercial buildings, including their individual components and construction considerations.

1. COMMERCIAL ROOFING SYSTEMS USED IN NORTH TEXAS

Because roofing is the most critical weather barrier—and the most commonly damaged from hail—North Texas requires robust, well-maintained roofing systems. Below are the dominant system types, each with its components and considerations.

A. TPO (Thermoplastic Polyolefin) Single-Ply Roofing

TPO is the most common roofing system for mid-rise offices in Dallas/Fort Worth.

Components:

• TPO membrane (45, 60, or 80 mil thickness)
• Mechanical fasteners or adhesive
• Polyiso insulation board
• Coverboard (typically gypsum-based like DensDeck)
• Flashings, boots, and heat-welded seams
• Termination bars

Advantages in North Texas:

• High solar reflectivity reduces cooling loads
• Welded seams offer strong wind resistance
• Durable against UV exposure

Challenges:

• Susceptible to hail damage depending on membrane thickness
• Poor installation can cause seam failures
• Adhesives may lose strength under long-term heat exposure

B. PVC (Polyvinyl Chloride) Roofing Systems

Less common than TPO but used in select buildings.

Components:

• Reinforced PVC membrane
• Hot-air welded seams
• Compatible adhesives
• Polyiso insulation
• PVC-coated metal for flashing

Benefits:

• Strong chemical resistance
• Performs well around kitchens, labs, or exhaust areas
• Excellent fire resistance

North Texas Notes:

UV exposure can cause plasticizer migration in older PVC membranes.

C. Modified Bitumen Roofing

Common on older buildings and some smaller mid-rise roofs.

Types:

• SBS (Styrene-Butadiene-Styrene)
• APP (Atactic Polypropylene)

Components:

• Base sheet
• Cap sheet (granulated or smooth)
• Torch-applied or cold-applied adhesives
• Flashing plies

Strengths:

• Highly impact resistant (excellent for hail zones)
• Multiple layers for redundancy

Weaknesses:

• Heavier and more costly than TPO
• Requires skilled installers
• Torch application risks fire if not managed carefully

D. Built-Up Roofing (BUR)

Older mid-rise buildings frequently have BUR systems.

Components:

• Multiple layers of asphalt and felt (plies)
• Gravel or mineral-surfaced cap
• Asphalt mopping
• Insulation below assembly

Why It Was Popular:

• Exceptional durability
• Heavy mass reduces hail damage

Challenges Today:

• Labor-intensive
• Difficult to repair cleanly
• Adds significant weight to roof structure

E. Metal Roofing Systems

Found on some mechanical penthouses or sloped architectural elements.

Types:

• Standing seam metal
• R-panel
• Architectural metal panels

North Texas Considerations:

• Highly durable but can dent significantly from hail
• Expansion/contraction from extreme heat requires slip joints and expansion clips
• Sealants must be UV-stable

2. ROOFING COMPONENTS & ACCESSORIES

Regardless of system type, all roofs require:

A. Roof Insulation

Polyiso is standard, often installed in multiple layers to reduce thermal bridging.

B. Coverboards

DensDeck or Securock improves fire resistance and hail resistance.

C. Flashings

Critical points where most leaks occur:

• Base flashings
• Curb flashings at RTUs
• Parapet wall terminations

D. Drainage Systems

North Texas roofs must accommodate intense rainfall events.

Includes:

• Internal drains
• Scuppers
• Overflow drains
• Tapered insulation systems

E. Roof Walkpads

Protect areas frequently accessed for equipment service.

3. FAÇADE SYSTEMS USED IN NORTH TEXAS MID-RISE BUILDINGS

Facades must withstand heat, sun, wind, and sudden temperature swings. Here are the primary systems:

A. Curtainwall Systems (Glass & Aluminum)

Very common in 1980s–2000s office towers.

Components:

• Vertical mullions
• Horizontal mullions
• Double-pane insulated glazing
• Gaskets and pressure plates
• Anchors and embeds

Failure Points:

• Gasket shrinkage from UV exposure
• Sealant deterioration
• Spandrel panel delamination

B. Storefront & Ribbon Window Systems

Used for lower floors or long horizontal glazing bands.

Issues:

• Sealant failures
• Leaky transitions between glass and opaque walls
• Settling causing frame distortion

C. Masonry Façades (Brick or CMU)

Brick is extremely common in North Texas mid-rise buildings.

Components:

• Brick veneer
• Air gap
• Weep holes
• Flashing
• Backup wall (CMU or sheathing)

Common Problems:

• Cracked brick due to soil movement
• Rusted shelf angles
• Missing or clogged weep holes
• Water intrusion from failed flashing

D. EIFS (Exterior Insulation & Finish System)

Popular in the 1990s and early 2000s.

Components:

• Foam insulation
• Base coat with embedded mesh
• Acrylic finish coat

Common Failure Points:

• Impact damage from hail
• Moisture intrusion at penetrations
• Poor detailing at windows

E. Metal Panel Systems

Used for accents and modern renovations.

Types:

• ACM (Aluminum Composite Material)
• Insulated metal panels
• Architectural corrugated panels

Concerns:

• Oil-canning from heat
• Sealant maintenance
• Water intrusion at laps

4. WATERPROOFING SYSTEMS & BELOW-GRADE ELEMENTS

Waterproofing is critical in preventing interior damage, mold, and structural deterioration.

A. Below-Grade Waterproofing

Used at basements, retaining walls, and elevator pits.

Common Systems:

• Self-adhered membranes
• Fluid-applied waterproofing
• Bentonite panels
• Sheet drainage boards

North Texas Challenges:

Expansive clay soils exert pressure on below-grade walls, stressing waterproofing systems.

B. Horizontal Waterproofing

Applied at:

• Terraces and balconies
• Planters
• Plaza decks

Components:

• Waterproof membrane
• Protection board
• Drainage mat
• Overburden (pavers, concrete, or landscaping)

Poorly installed terrace waterproofing is a leading source of leaks in older buildings.

C. Sealants & Joint Systems

Sealant failure is the number one source of façade leaks.

Types of Sealants:

• Silicone (best for UV resistance)
• Polyurethane
• Hybrid sealants

Joint Types:

• Expansion joints
• Control joints
• Window perimeter joints
• EIFS joints

North Texas heat cycles accelerate sealant aging.

5. HAIL, WIND & WEATHER RESILIENCE

North Texas is one of the most hail-prone regions in the U.S.

Roofing Responses:

• Thicker membranes (80-mil TPO)
• Hail-resistant cover boards
• Impact-rated shingles on sloped roofs
• Upgraded metal-panel gauges

Façade Responses:

• Impact-resistant glazing
• Reinforced EIFS
• Metal panel replacement

6. ROOF & FAÇADE INSPECTIONS

Typical inspection methods include:

• Infrared scanning for moisture under membranes
• Aerial drone inspections (common since 2018)
• Moisture meters and probes
• GPR scanning around penetrations
• Water testing at windows

7. ENVELOPE RETROFITS & MODERNIZATION

Owners often upgrade the envelope to improve building value.

Common Upgrades:

• Re-cladding façades with metal or fiber-cement panels
• Replacing outdated glazing with low-E insulated glass
• Repainting or refinishing EIFS
• Adding canopy structures
• Roof replacements with upgraded insulation for energy efficiency

8. COORDINATION DURING OCCUPIED BUILDING WORK

Envelope work must avoid disrupting tenants.

Requirements:

• Noise control
• Protecting rooftop equipment during removal
• Maintaining water-tightness during phased work
• Coordinating temporary shutdowns for tie-ins
• Scheduling crane lifts during weekends