Best Practices for Managing Wood Frame Construction Risks

Best Practices for Managing Wood Frame Construction Risks Contributors: Roger Attanasio, Dylan Towe, Scott Sampson, Chuck Ciesar, Andrew Jamison, Robbie Sutton, John Hughes, Meredith Ray, Katherine Ball

Best Practices for Managing Wood Frame Construction Risks: Contributors: Roger Attanasio, Dylan Towe, Scott Sampson, Chuck Ciesar, Andrew Jamison, Robbie Sutton, John Hughes, Meredith Ray, Katherine Ball

Issues to Consider with Wood Frame Construction:

Abstract

Architect and Consultant Team

Decisions associated with utilizing wood frame construction can

A design team with knowledge and experience in wood frame

substantially impact the long-term success of a project in terms of performance, costs, durability, maintenance, and potential exposure to litigation.

Background

construction issues is paramount. LS3P requires the Architect engage, and hold contracts for, the MEP, structural, envelope, waterproofing, accessibility, and acoustic consultants. Specialty consultants such as pool or food service may be required depending on the project scope. Civil/landscape consultant contracts could potentially be held

Wood frame construction has become a commonly used construction

by the Owner; however, better coordination can be achieved with the

type, particularly in multifamily residential and mixed-use markets.

Architect holding those contracts as well.

Clients typically choose wood framing for its presumed economy, flexibility, and speed of construction. However, this construction

The envelope and accessibility consultants engaged by the Architect

type comes with serious potential issues which must be identified,

are hired for design review services. LS3P also requires the Owner

discussed, agreed upon, and managed from the earliest stages of

hire envelope and accessibility consultants for field review during

design through construction. The decision to utilize wood frame

construction to field-verify “as-built” conditions.

construction requires an investment in consistently scheduled and performed building maintenance for the lifespan of the structure.

Construction Quality Successful wood frame projects require experienced contractors, a realistic project and construction schedule with adequate time for coordination, careful attention to details during both design and

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construction, proper tolerances, and a rigorous QA/QC process.

mold issues, damage to interior finishes, structural degradation, and

Conversely, inexperienced contractors and subconsultants, compressed

health concerns for building occupants.

schedules, code minimum designs, and failure to coordinate details and verify proper execution of those details can lead to long-term issues

Mold

including premature and additional building maintenance, expensive

Regions subject to high humidity, heavy / prolonged periods of rain,

remediation, and in extreme instances, litigation.

and resulting standing water on the wood framing/subfloors introduces the possibility of mold growth on all exposed wood framing. Mold

Exterior Envelope / Skin Materials

remediation and treatment is both costly and time consuming and can

Exterior envelope material selection is critically important for the

negatively impact the construction schedule. Specification of mold

long-term performance of this construction type. Some envelope

inhibitors and the requirement for a Contractor’s mold management

systems are more compatible with wood frame construction than

plan shall be included in LS3P construction documents.

others; systems such as Exterior Insulation Finish Systems (EIFS) or stucco, when detailed or installed improperly, have proven to be

Sound Attenuation

costly in terms of water intrusion, remediation and litigation. Selection

Particular care must be taken to minimize sound transfer between

of exterior envelope materials for performance over initial cost is

units and public spaces and between individual units. Designing

imperative for the long-term success of the project. Materials such as

and constructing assemblies with sufficient sound attenuation

masonry veneer, cementitious siding, and metal panels have proven

characteristics is critical for occupant privacy and satisfaction. Note

effective on past LS3P projects. Value engineering of the exterior

that acoustical performance of wall and floor / ceiling assemblies is

envelope, including the roof, is strongly discouraged.

often compromised when resilient furring strips are incorrectly installed.

Management of the veneer attachment to the structural system and

LS3P recommends “sample units” be included to field test the

moisture control for the entire building envelope is critical.

designed/selected assemblies to verify achievement of desired performance characteristics.

Water Intrusion Careful attention to exterior envelope detailing during design AND

Fire Protection

construction will help minimize this construction type’s vulnerability to

Compliance with life safety and fire protection in wood frame

water intrusion. Decisions based primarily on economics and failure

construction presents unique challenges. Stringent fire codes for

to adhere to best practices for minimizing water intrusion can lead to

rated walls and separations may involve assemblies with increased

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wall thickness which can, and often do, affect items such as vertical plumbing and mechanical shaft sizes, sprinkler head placement, and accessibility. Placement of a stud wall 1/2” off here or 3/4” off there can make all the difference in complying with code, meeting an Owner’s desire for minimum rentable unit area, and complying with accessibility requirements. Designing to code minimums may cause significant challenges in meeting accessibility requirements, thus it is preferable to provide tolerances and design slightly beyond code/ statute minimums. It is important to coordinate fire partitions, fire barriers, fire walls, smoke partitions, and smoke barriers carefully to

penetrated and therefore require dropped soffits; vertical shafts on

distinguish each condition and how it relates to other rated assemblies

architectural and structural coordinated with mechanical and plumbing

such as floor/ceiling, roof/ceiling and expansion joints.

for routing of plumbing, mechanical and storm water piping and vertical ducts; clearance at cutout for horizontal piping due to wood

Shrinkage

stud shrinkage; detail consideration at envelope openings that resolve

Shrinkage of wood framing members due to drying of wood can

concurrent wood framing shrinkage and brick veneer expansion;

have significant impact on the performance of the building envelope.

and fire code requirements impinging on accessibility clearances

Some wall veneer materials such as brick expand while cementitious

and horizontal exits, which are a common practice in mid-rise wood

materials shrink at lesser rates than wood framing, putting greater

construction. These details can require specialized framing and hangers

stress on wall sealants and making envelope inspection and

that can quickly add cost to a project if not properly coordinated.

maintenance more important. Understanding how the different materials will react relative to each other over time is an essential

On larger wood frame projects, require truss manufactures to provide

component for a successful design.

BIM Coordination capabilities, and include in the specifications a truss/MEP/FP BIM coordination meeting to have initial results

Coordination Successful wood frame construction requires close coordination among all trades (and reasonable time built into the schedule for that

presented to the design team, GC and impacted subs, prior to final truss shop drawing submission.

coordination) to reduce potential conflicts. A few examples of this

Pest Control

include mechanical and structural coordination for horizontal duct

Wood is by nature vulnerable to insect infestation, including ants,

routing with locations of engineered lumber members that cannot be

roaches and termites. Insect infestation can quickly cause occupant

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dissatisfaction, added maintenance time, expense, and potentially

project could be converted to a condominium, LS3P recommends

significant structural damage requiring costly remediation. Owners

language be included in the HOA Documents addressing the

should prepare and implement a preventative maintenance plan for

conversion to protect the Owner/Developer and Architect from future

insect management for the life of the building.

HOA/third party claims.

Owners must provide documentation of termite treatment, including a pre-installation conference for coordination, reapplication after a significant rain event, and monitoring for a specified period of time after substantial completion. LS3P recommends that termite chemicals be tinted when applied for verification.

Service Life Expectancy Wood frame projects which focus on quality design, material selection, best practices during construction, and adherence to a regular maintenance program can reasonably expect a successful long service life. Owners of wood frame projects which do not place an emphasis on these critical issues at every phase of design, construction, and occupancy should expect building issues which significantly diminish their return on investment and useful service life. Development of a “maintenance manual” for the Owner’s use in scheduling regular maintenance is highly recommended. This maintenance manual should include a yearly inspection of the exterior envelope.

Litigation Implementing best practices for the design, construction, and operation of wood frame buildings will help to minimize potential exposure to litigation for the Owner, Architect, and Contractor over the life of the building. IF in the future there is a possibility that your

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Best Practices for Managing Wood Frame Projects During Construction

• Avoid subcontractor requests for extensive changes to the design detailing of floor framing structure, for example top chord vs. bottom chord bearing floor trusses. These requests sometimes do not account for the collateral issues caused by the change

ENGAGE QUALIFIED CONTRACTOR AND SUBCONTRACTORS

request. Additionally, the requests are usually not made in a timely

Engaging a contractor and, specifically, framing subcontractors with

manner and a quick decision on one component can create other

verified experience in wood frame construction is critical to long-

unintended problems.

term project success. Experienced contractors are best equipped to manage the challenges of this project type and minimize issues both during the construction process and as the building ages, when construction quality becomes more evident over time. Construction

MINIMIZE OPPORTUNITIES FOR WATER INTRUSTION

experience must include Type III construction and not just Type V- or

Envelope / Waterproofing Consultant

single-family residential experience.

In addition to verified wood frame construction experience, the contractor should have available adequate financial and manpower resources to procure and manage the materials and workforce to meet the proposed construction schedule.

• The framing subcontractor is a vital part of the wood frame construction team, which must be highly experienced and must have verified qualifications. LS3P recommends framing subcontractors be prequalified and “bonded.” The selected framing subcontractor should NOT be permitted to hire a thirdtier subcontractor to complete their work. Should the scope of the project require multiple framing contractors, it is critical to ensure that the work can be compartmentalized per framing sub to maintain accountability.

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LS3P requires engaging a waterproofing consultant for the building envelope and prefers the contract for these services be held by LS3P to maintain close communication throughout design and construction.

Building Envelope Selecting a cladding system with a long history of demonstrated compatibility with wood frame construction is paramount. EIFS and three-coat stucco, when detailed and installed incorrectly, have been known to be problematic in terms of water intrusion, expensive remediation, and litigation. Cementitious fiber siding/board, masonry veneer, and metal panels have provided proven, repeatable service in wood framing construction. Fiber cement products are available in lap siding, board and batten, and shake styles and the material is workable, affordable, and provides consistent elevations. The Contractor must have a verified good working knowledge of the envelope system selected.

Moisture and Mold Mitigation Plan

the plywood. Fluid-applied air barriers come in various thickness or

Having a Contractor-provided moisture and mold mitigation plan in

mils and should be coordinated with the project specifications and

place prior to the start of construction is required. This plan should

details.

include mold pretreatment and/or mold mitigation products in every project

Protection / Storage of Materials

specification. (For example, Anabec

Proper storage of materials on the

NewBuild 50 is a commercial moisture

construction site, from delivery through

barrier that has been used successfully on

installation, is an issue often overlooked.

recent wood frame projects; this product

Wood delivered to the site containing

has an unobtrusive lightly white tint.) A clear

mold, improperly stored on-grade, or

penetrating water repellent is recommended

covered in a manner resulting in mold

for application to plywood and OSB

formation after rain events are issues

floors, or a product similar to Advantech

requiring discussion with the Contractor

which is tolerable to exposure of water without delaminating is

and monitoring throughout construction.

recommended. Having the mold mitigation plan in place results in

Lumber must be stored above ground a

faster implementation and reduces construction schedule disruptions.

minimum of 4” and covered in a manner that allows the lumber to breathe. Stored material containing mold

Fluid-Applied Moisture Barrier

should be treated prior to installation or discarded. Projects located in

LS3P specifies and strongly recommends a fluid-applied moisture

disaster-prone regions should be scheduled and sequenced to protect

barrier or similar product in lieu of sheet commercial-wrap products

structures and contents in high-risk seasons.

such as Tyvek. Concerns with sheet commercial-wrap products include improper detailing and installation at windows and

Detailing

penetrations, damage resulting from wind and exposure time during

Detailing and construction of the exterior envelope, including the

construction before the sheet product is concealed, and the inability

roof, are two of the most important aspects for a successful project.

to limit water intrusion to a specific location. Reliance on taped joints

Flashing around windows, pipe and conduit penetrations, the

rather than a fully integral air/moisture barrier is a weak point of sheet

intersection of balcony and exterior walls, expansion joints, exhaust

wrap type systems. LS3P also recommends specific attention be

vents, railing attachments, parapet coping, dormers, valleys, and roof

provided to the fluid-applies air barrier system during application,

curbs are examples of assemblies requiring specific details to prevent

as inadequate coverage can be an issue due to the rough texture of

moisture/water intrusion. The type of window selected, for example

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residential with nail fin, aluminum punched opening, storefront or

must be provided to designing and constructing acoustical separation

curtainwall, will require specific flashing details. The detail for each

between units and common elements and between individual units.

type noted is significantly different. Detailing the sill condition between

Assemblies should exceed code minimum of STC 50 and IIC 50 (45 if

interior finish floor level and exterior balcony is critical not only for

field tested) separating dwelling units and sleeping units from public/

water intrusion, but also for accessibility requirements. Designing

service areas.

occupied space below an exterior balcony presents challenging detailing opportunities to prevent condensation and water intrusion

Specifications should include field testing of STC and IIC for floor/

issues. The list can be infinite depending on the Owner’s program and

ceiling assemblies and walls by an acoustical engineer. Field testing

Architect’s design. Collaboration between the Owner, Architect, and

should include an early mockup within the building; owners and

Contractor is essential for a well-conceived, well-designed, and well-

contractors should be aware that this field testing will impact the

constructed exterior envelope.

construction sequence and will come with an associated cost.

Construction Protocols:

HVAC LS3P recommends the contractor

Avoid natural ventilation to achieve required air changes. Provide a

follow a few seemingly simple, but

mechanical fresh air system.

often overlooked daily procedures which, if followed, greatly assist in the

Sample Unit

prevention of moisture and mold issues

LS3P strongly recommends a “sample” unit be included as part of

during construction. These include a

the QA/QC process for Contractor/Owner verification. If multiple unit

daily clean-up of the construction site;

types are involved this may require multiple sample units.

removal of lumber scraps, sawdust, and other debris; sweeping floors each day after work concludes; and removing standing water immediately after each rain event for control of mold and excessive moisture content.

Acoustics Hearing a neighbor through the walls is a common occupant complaint in multi-family residential wood frame projects. To increase privacy and comfort and minimize noise issues, specific attention

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Exterior Mock-up A mock-up of the exterior wall with all typical conditions is also required, including a full-size window unit for possible testing. Careful attention must be paid to the transitions between exterior finishes.

Implement QA / QC Strategies LS3P recommends the Contractor develop and implement a QA plan/QC measures during construction. Along with the contractor

QA/QC, LS3P recommends the Owner engage independent consultants/inspectors to monitor framing work, exterior wall assemblies, and accessibility issues in progress during construction.

In addition to the noted procedures LS3P and its consultants will be performing construction contract administration, which involves observing work in place at predetermined intervals. Please note that work will continue between the design team’s site visits and monitoring by the independent consultants/inspectors is beneficial for the project.

Conclusion Adherence to best practices for design, construction, operation and maintenance of wood frame projects is the best way to reduce potential serious issues with construction quality, water intrusion, sound attenuation, fire protection, building envelope, insect infestation, service life, and litigation. A successful wood frame project will require an investment in quality construction; an experienced team of designers, contractors, and consultants; and a commitment to coordination, quality assurance/quality control, and communication among all team members.

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