Guide to EIFS Stucco

 

For the homeowner, stucco is a term loosely applied to various kinds of plasterwork, both exterior and interior. The most

common use is to refer to plaster or cement used for the external coating of buildings. Hard Coat Stucco consists of a

mixture of cement or lime, sand and water, applied in one or more coats over rough masonry or frame structures.

 

Synthetic versions of stucco have come into wide uses that include acrylic resins or polymers. The most common type is

known as Barrier EIFS (Exterior Insulation and Finish System). EIFS has been used for a little over three decades in

the USA. It was developed in Germany during the 1950's to assist in the re-building of Europe after World War II. EIFS

combines exterior finish system durability with good thermal insulation and a variety of texture color retention. In the late

1990's EIFS manufacturers started to develop and market a second generation of PB-EIFS for wood frame

construction. These are often generally referred to as Moisture Drainage EIFS or MD PB-EIFS.

 

Hard Coat Stucco (HCS) has been used for decades; traditionally three coat stucco has a long history that is well

accepted and defined in the Model Building Codes. The newer One-Coat Stuccos (OCS) are thinner with proprietary

mixes that require code body evaluation service reports for local building officials to review and allow use of products in

their jurisdiction.

 

Traditional Stucco facts:

 

                 ·  A Moisture Barrier is required on top of moisture sensitive substrates such as wood, gypsum, etc.

                 · Three coats or layers with a total thickness of 3/4 of an inch or more - Scratch Coat, Brown Coat, and Finish

               Coat.

                 · Metal Accessories - Casing Beads or Stops or Grounds, Weep Screeds, Corner Aids, and Control Joints or

              Expansion joints at 144 square feet.

                 · Flashings are required as a part of weatherproofing the system.

                 · Vulnerable to excessive cracking.

                 · Details are well developed; see Northwest Walls and Ceiling Bureau Stucco Resource Guide.

 

One-Coat-Stucco is a newer stucco system that is very similar to traditional stucco but with some advantages. It provides

design flexibility, durability and water management. It can also be finished in a variety of ways including premixed colored

cement stucco finish coats, elastomeric coatings and paints or even acrylic textured finishes.

 

Each one-coat stucco system is a proprietary mix of Portland cement, polymers, fiber reinforcement and secret

ingredients. Each approved One-Coat-Stucco has its own Evaluation Report by the various Model Codes (the Model

Codes have recently been merged into one Model code, ICC or IRC). Note: The One-Coat-Stucco name is a misnomer

since there are actually at least two coats.

 

                 · A Moisture Barrier is required on top of moisture sensitive substrates such as wood, gypsum, etc.

                 · One-Coat-Stucco is applied in coats with a total thickness of 3/8 to 1/2 inches - a brown or base coat and a finish

              coat.

                 · Metal Accessories - Casing Beads or Stops or Grounds, Weep Screeds, Corner Aids, and Control Joints and

              Expansion joints at 144 square feet, window and door corners and per architectural details.

                 · Flashings are required as part of weatherproofing the system.

                 · Vulnerable to cracking. Although, if mixed and installed properly, the proprietary mixes are very effective at

              minimizing cracking.

                 · Details are typically well developed and part of the Evaluation Report or the Manufacturer's installation

              manuals. See the Northwest Walls and Ceiling Bureau Stucco Resource Guide for further clarification.

 

EIFS (Exterior Insulation and Finish System) or Synthetic Stucco

 

Since EIFS is a non-load bearing exterior wall system, the system's primary function is to provide a weather barrier,

thermal insulation and an attractive exterior cladding. When properly installed and maintained, the system will provide

many years of beauty and function.

 

The two basic types of EIFS are Barrier EIFS and the newer Moisture Damage EIFS. Both systems require following

the manufacturer's installation details carefully.

 

Barrier EIFS has been used for over three decades in the USA. Most EIFS used on residences were PB EIFS (Polymer

Based). Each system is a proprietary mix and has its own Evaluation Report by the various Model Codes (The Model

Codes have recently been merged into one Model code, IBC or IRC)

 

                 · System Components:

              o EPS (Expanded Polystyrene) insulation properly attached to substrate or framing.

              o EPS properly prepared to receive basecoat.

              o Polymer Based basecoat applied to EPS.

              o Fiberglass mesh immediately embedded into fresh basecoat.

              o Finish Coat properly applied to cured basecoat.

                 · No PVC or metal Accessories; however, edges must be properly back-wrapped to protect the EPS and minimize

               damage.

                 · Details have developed over the past 30 years by the individual manufacturers and EIMA.

 

Moisture Drainage EIFS

 

The newer Exterior Insulation Finish system, Moisture Drainage EIFS, uses a drainage plane and moisture barrier on top

of the moisture sensitive substrates. Each system is proprietary and has its own Evaluation Report by the various Model

Codes. As was stated above, the Model Codes have recently been merged into one Model code, IBC or IRC. A moisture

barrier is required on top of moisture sensitive substrates such as wood, gypsum, etc.

Moisture Drainage EIFS System Components are very similar to Barrier EIFS

                

                 · EPS (Expanded Polystyrene) insulation properly attached to substrate or framing.

                 · EPS properly prepared to receive basecoat.

                 · Polymer Based basecoat applied to EPS.

                 · Fiberglass mesh immediately embedded into fresh basecoat.

                 · Finish Coat properly applied to cured basecoat.

                 · Flashings, at roofs, decks, windows and doors, are required as part of weatherproofing the system.

                 · A sheet or liquid applied moisture barrier.

 

The significant difference, in addition to the Moisture Barrier, is the use of PVC Accessories.

                

                 · PVC Weep Screeds at bottom of all walls and above windows, doors, decks or doors

                 · Horizontal Expansion Joints must allow for the drainage of moisture.

                 · Flashings are required as part of weatherproofing the system.

 

Properly installed EIFS Moisture Drainage systems should also be resistant to cracking. The details are typically well

developed and part of the Evaluation Report or the Manufacturer's installation manuals.

 

Proper care and maintenance of the exterior cladding of a home will help the homeowner maintain the value and curb

appeal of the property.

 

The ideal situation would be to have the Exterior Cladding on your home inspected as it is being applied

to the house. However, that may not be possible in many situations. An inspection by a Certified Third-

Party EIFS Inspector or Certified Moisture Analyst would provide the necessary information to assist you

in establishing the condition of and maintaining the integrity of your home. The purpose of this inspection

is to look for visible installation flaws, inadequate water diversion, and sealant failures and, if necessary,

conduct moisture readings as appropriate using electronic moisture devices and substrate evaluation.

 

Moisture intrusion problems are not limited to stucco claddings. Time of exposure coupled with the

quantity of water, result in problems for any home. In our area, many of the homes combine stone,

fiberboard, wood, cement board or vinyl siding, brick, and various types of stucco. For example, hard coat

stucco exteriors may have stone veneer below decorative bands along with a variety of other decorative

features.

 

Barrier PB EIFS Exterior:

When you hear people talking about problems with EIFS, this is the style of EIFS typically having the

problems discussed. The objective is to prevent moisture from entering the system. Barrier-type EIFS is

a system that relies entirely on its outside surface to prevent water penetration and moisture intrusion.

Therefore, excellent design, compatible quality materials and excellent workmanship are required to

produce a weather-tight and long-lasting system.

 

Moisture Intrusion may occur at the following:

 

Windows and doors - Points of concern to be evaluated

 

                 · Look for peeling paint, evidence of water damage on the interior wall, staining on the exterior.

                 · Check for calking around window sills and door jams. Stucco manufacturers recommend a

               specific sealant for their windows

                 · Is sill pan flashing present or is it needed?

 

Flashings:

 

                 · Flashings at appropriate places direct water away from the house.

                 · Missing, improper or unsealed flashings where roof lines terminate into an EIFS wall will allow

               roof run-off to be dumped directly behind the EIFS.

                 · Water must be directed away from windows, decks, gutters, etc.

 

Caulking:

 

                 · Penetrations in the EIFS at decks, hose bibs, dryer vents, light fixtures, satellite dishes, etc. must

               be properly sealed with the appropriate sealant.

                 · All joints where EIFS meets a dissimilar material must be sealed with the appropriate sealant.

                 · Existing sealants should be adhered, soft and flexible.

 

Installation Issues:

 

                 · Foam insulation should be at least 6 inches above soft grade and two inches above hard

               surfaces. This prevents wicking of moisture and eliminates a termite path into the structure.

                 · The foam substrate should be properly back-wrapped in order to provide for proper protection of

               the exterior system.

                 · The usage of backer rod and sealant is necessary for the proper construction of an isolation type

               of joint such as windows, expansion joints and grade terminations.

                 · EIFS used on non-vertical surfaces such as trim and decorative touches should have a sloping

               surface to prevent standing water.

 

All EIFS manufacturers have details and procedures that builders and applicators are expected to

follow. Installation details are similar among the various EIFS products; however, there are some

differences.

 

Moisture Drainage PB EIFS:

 

This is the second generation of PB EIFS. The difference is that MD PB EIFS has a secondary moisture

resistive Barrier to control incidental moisture that gets through the EIFS Exterior Barrier and permits it to

drain out the bottom of the system. The MD EIFS should be installed such that all water will again be

shed at the exterior surface and a secondary moisture resistive barrier to handle any moisture that gets

past surface barriers.

 

Hard Coat Stucco (Traditional or OCS)

 

These systems also have drainage planes; however, if detailed improperly, they can also have moisture

problems.

 

What can I look for that would indicate that I may have a Moisture Intrusion problem in an Existing

Home?

 

Check for the following items. If they are observed, further investigation is suggested.

 

                 · Does the caulking properly seal stucco to window and door frames?

                 · Is there staining on the stucco walls below where gutters end?

                 · Is there cracking or bulging in the stucco? Is the stucco loose or soft?

                 · Are there any penetrations in the stucco that are not properly sealed, i.e. decks, railings, vents,

               pipes, logs, etc.?

                 · Are there visible signs of water damage on interior walls, ceilings or floors?