Water Infiltration Control During Building Construction: Temporary Protection Strategies for Roof Assemblies and Vertical Enclosures

The Hidden Risk of Bulk Water During Active Construction

A primary design goal for any building enclosure is to minimize bulk water infiltration into the intended dry zone of enclosure assemblies throughout their service life. Yet one of the most overlooked aspects of achieving this goal is controlling water during the project’s construction phase itself. While considerable attention is given to final weatherproofing and long-term moisture protection of completed buildings, the interim period when roof assemblies remain open and vertical enclosures are partially finished presents a critical vulnerability.

Building professionals who have dealt with wood frame roof assemblies moisture management challenges understand that water entering incomplete work can lead to premature degradation of moisture-sensitive materials, increased potential for organic growth, decreased thermal resistance, and elevated interior moisture levels that persist for years after occupancy. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) acknowledges in its Fundamentals Handbook that built-in construction related moisture can be a significant moisture source during the first years of a building’s use.

Understanding Water Pathways in Partially Completed Enclosures

How Bulk Water Migrates Through Open Construction

During construction, the building enclosure is inherently incomplete for extended periods. Roof decks may be framed but not yet fully weatherproofed. Wall assemblies may have exterior sheathing installed without the final cladding or weather-resistant barrier. Openings for windows, doors, and mechanical penetrations remain unsealed. These conditions create multiple pathways for bulk water entry that would not exist in a completed building.

Rain events during construction can drive water into partially completed assemblies in several ways:

• Direct wind-driven rain entering through unglazed openings and unfinished roof edges
• Water running down vertical surfaces and pooling at unfinished transitions between assemblies
• Capillary action drawing moisture into porous materials such as concrete masonry units (CMU) and gypsum sheathing
• Water migration through incomplete air and vapor barrier systems at tie-in locations
• Accumulation of ponding water on horizontal surfaces such as roof diaphragms and floor slabs before drainage is operational

Consequences of Uncontrolled Water Infiltration

When bulk water enters completed portions of the enclosure during construction and is subsequently trapped behind finished materials, several performance issues can arise:

1. Material degradation – Wood roof trusses and framing members exposed to prolonged moisture can develop rot, fungal decay, and dimensional instability that compromises structural performance
2. Thermal performance loss – Wet insulation loses its R-value, and moisture trapped within insulation cavities can remain for extended periods, reducing energy efficiency
3. Biological growth – Persistent moisture creates conditions for mold and mildew growth within concealed wall and roof cavities, leading to indoor air quality concerns
4. Corrosion – Metal connectors, fasteners, and flashing elements can corrode when exposed to moisture in trapped conditions
5. Delayed project completion – Water-damaged materials often require removal and replacement, causing schedule delays and cost overruns

Specifying Temporary Weather Protection in Construction Documents

Contractual Responsibility and Cost Allocation

One of the most significant challenges in managing water infiltration during construction is the absence of clear specification language assigning responsibility for temporary weather protection. When specifications lack explicit requirements, confusion arises among trades about who should implement protective measures and who bears the associated costs.

To address this, project specifications should include dedicated sections addressing temporary weather protection requirements. These specifications should define:

• Which enclosure assemblies require temporary protection and at what stage of completion
• Acceptable materials and methods for temporary tie-ins and terminations
• Performance criteria for temporary barriers, including wind resistance and water hold-out capability
• Inspection and acceptance protocols before work can proceed past critical stages
• Responsibility for maintenance and repair of temporary protection systems throughout construction

Learning from Roofing Industry Practices

The roofing industry has long recognized the importance of maintaining watertight conditions for partially completed work. Standard specifications routinely limit roof assembly installation to areas that can be made weather-tight by the end of each day’s work. Temporary terminations are installed to prevent bulk water entry into completed portions, then removed when work resumes. This process repeats throughout the roof assembly installation until completion.

The same disciplined approach should apply to vertical enclosure assemblies, yet it frequently is not. Weather resistant barrier specifications for building envelope moisture management provide an excellent starting point, but they typically address the final installed condition rather than the interim construction period.

A comparison of protection approaches across different assembly types highlights the gap:

Implementing Effective Temporary Protection Protocols

Pre-Construction Planning and Sequencing

Effective temporary weather protection begins during pre-construction planning. The project team should review the construction sequence for each enclosure assembly and identify periods when completed work will be vulnerable to water exposure. These vulnerable periods should be documented in the project schedule, and specific protection measures should be assigned to responsible trades.

Key considerations during pre-construction planning include:

• Seasonal weather patterns at the project site and their impact on construction sequencing
• Orientation of the building and exposure to prevailing wind-driven rain
• Complex geometric transitions between different enclosure systems that require custom tie-in detailing
• Lead times for temporary protection materials to ensure availability when needed
• Coordination between structural, enclosure, and MEP trades to avoid creating unprotected openings

Quality Control During Construction

The most carefully specified protection measures are only effective if they are implemented and maintained throughout construction. Quality control procedures should include regular inspections of temporary protection systems, particularly before and after anticipated rain events.

The project team should establish protocols that address:

• Daily inspection of temporary barriers at the end of each work shift
• Rapid response procedures for repairing damaged or dislodged protection
• Documentation of protection status through photographs and inspection reports
• Procedures for evaluating potential water intrusion after rain events before enclosing work
• Remediation protocols if water infiltration is discovered in completed assemblies

Temporary Tie-In Detailing for Complex Interfaces

Complex geometry and transitions between different enclosure systems require carefully designed temporary tie-in details. These details are often omitted from construction drawings, leaving field crews to improvise solutions that may not provide adequate protection. For projects with complex enclosures, temporary tie-in details should be developed during the design phase and included in the construction documents.

Common interfaces requiring temporary tie-in detailing include curtain wall-to-floor slab transitions, roof-to-wall intersections, expansion joints crossing different assembly types, and penetrations for mechanical louvers and exhaust vents. Each interface requires a specific temporary protection strategy that addresses the unique geometry, exposure, and sequencing of work at that location. For existing structures undergoing renovation, repairing wood roof trusses in historic masonry buildings presents additional challenges because the original structure may lack modern moisture management provisions, yet must remain protected during extensive repair work.

Material Selection for Temporary Weather Protection

Choosing the Right Temporary Barrier System

The selection of temporary weather protection materials should be based on the duration of exposure, expected weather conditions, and the sensitivity of the materials being protected. Options range from simple polyethylene sheeting to engineered temporary membrane systems designed to withstand wind loads and repeated wetting.

• Polyethylene sheeting – Low-cost option suitable for short-term protection of small areas; limited durability and wind resistance; must be properly secured to prevent tearing and wind uplift
• Reinforced polyethylene and woven fabrics – Increased tear resistance and durability; suitable for medium-term protection of larger areas; available in various weights and UV-resistant grades
• Self-adhering membrane sheets – Provide watertight seal at temporary termination points; commonly used for roof edge tie-ins and critical transition areas; can be left exposed for extended periods
• Fluid-applied temporary membranes – Applied as liquid that cures to form a continuous barrier; ideal for complex geometries and irregular surfaces; requires proper surface preparation and cure time

When designing temporary protection for sensitive assemblies, consider the compatibility of temporary materials with permanent system components. Some adhesives and sealers used in temporary membranes can leave residues that interfere with permanent waterproofing adhesion. For permanent solutions, consult resources on fluid applied waterproofing membranes for building envelope specification to understand how temporary and permanent systems can be coordinated.

Inspection and Maintenance Protocols

Temporary weather protection systems require ongoing inspection and maintenance throughout the construction period. A designated member of the project team should be responsible for monitoring protection systems and coordinating repairs. Inspection frequency should increase during periods of predicted severe weather, and all inspections should be documented.

An effective inspection protocol includes:

1. Daily visual inspection of all temporary barriers and tie-ins at the end of each work shift
2. Inspection immediately before and after each significant rain event
3. Prompt repair of any damaged, dislodged, or deteriorated protection components
4. Documentation of all inspections and repairs in the project quality control log
5. Communication of protection status at regular project coordination meetings

By implementing these protocols, building professionals can significantly reduce the risk of moisture-related problems that can compromise building performance, delay project completion, and lead to costly remediation work. The investment in temporary weather protection represents a fraction of the cost of repairing water-damaged assemblies and addressing the indoor environmental issues that result from uncontrolled water infiltration during construction.