Typical Details for Residential Construction

  • Home
  • Typical Details for Residential Construction

Typical Details for Residential Construction

MINIMUM REQUIREMENTS FOR DURABLE EXTERIOR INSULATION AND FINISH SYSTEMS

Foreword

The material and application requirements outlined here are considered by the authors to be the minimum standards necessary to achieve a durable exterior insulation and finish system (EIFS) having a reasonable service life without excessive maintenance and repair costs. These requirements pertain a wide variety of Exterior Insulation Finish Systems.

These requirements are not intended to be complete or sufficient by themselves, but are to be used to provide guidance in the absence of contract documents or manufacturer’s requirements. The details provided are not extensive. Every project must be designed, detailed, and specified as the specific job conditions require.

 

Design Considerations

Substrates

Acceptable substrates for adhesively attached or mechanically fastened for exterior wall claddings are:

  • Poured or pre-cast concrete,
  • Masonry including brick, block, existing stucco, and ASV (Adhered Stone Veneer)
  • cement based sheathing boards.
  • Gypsum base sheathing boards.
  • Wood and wood fiber sheathing boards
  • Other specific manufacturer approve other substrates

Sills and Parapets

Positively pitched to drain, preferably 6-inch 9n 12-inch at horizontal surfaces.  Most manufacturers call for a 1:2 slope minimum. Steeper slopes are preferable.

Metal sills and parapet copings are also permitted and even preferred.

Impact Exposure

High impact areas may require impact resistant reinforcing to the wall cladding

Three degrees of exposure to impact and abuse are generally recommended:

  1. Low Exposure: Walls above the first floor with no direct access are acceptable with a single layer of standard weight mesh.
  2. Medium Exposure: Balcony walls and similar areas should have a double layer of standard weight mesh.
  3. High Exposure: Ground floor walls should have high impact mesh and standard mesh. Walls at high traffic areas, such as public and apartment building entrances, areas facing pavement or play spaces, and loading docks, should not be clad with PB EIFS. PM EIFS or other stronger cladding systems should be used at high traffic areas.

Foundations

EIFS systems are not generally permitted below grade. The primary reason is that termites and carpenter ants use the insulation as a home or conduit for entry into the structure. If used below grade the backfill must be gravel (ie. well drained.)

Penetrations

All penetrations must be made watertight. It is important to detail the weatherseal at all penetrations and edge conditions. Vinyl edge track, backwrapping, preformed sealant tape, and overlapping flanges are acceptable details when appropriately used.

 

Materials

Repair materials should meet or exceed the wall cladding materials already on the building these materials may include but are not limited to:

  • Insulation Board
  • EPS Board Adhesive
  • Base Coat
  • Reinforcing Mesh, netting or lath
  • Tie Coat
  • Finish Coat
  • Base Coat Primer
  • Textured Finish
  • Sealant Tape and
  • Caulk Sealants
  • Vinyl Accessories

 

Repair Application

Insulation Board

Insulation board joints must be offset from sheathing joints and from any aesthetic joints that will be cut into the insulation board. Insulation boards must not align with the edges of windows, doors, or similar openings. Inside and outside corners should be interlocked to prevent cracking.

Insulation boards must butt tightly with no gaps between boards. Gaps 1/16″ and larger must be filled with slivers of insulation board or a manufacturer approved foam. Gaps between boards should not be fill with base coat material; base coat in these gaps are a common cause of cracking.

Base Material

It is important not to add more water or cement than the manufacturer recommends. The material must be thoroughly mixed using screened cement to avoid lumps. Non-cementitious base coats must be used only on substrates for which they are approved. Allow sufficient time for the base to cure.

Base Application – Low Impact Exposure

The minimum acceptable base coat thickness is 3/32″ (2.4 mm). This is a minimum threshold at any point and not a minimum average thickness.

It is often specified that the base coat be applied in two layers, not in a single application. Approximately 1/16″ of material is applied to the EPS board. The reinforcing mesh is then troweled onto the surface of the base coat. Mesh pattern and small areas of mesh color may be visible. Often, a second layer of base material is applied to completely embed the mesh. Any areas of visible mesh pattern must be skim coated with additional material.

Mesh should be double at all corners. Mesh laps should not align with edges of window, door, and similar openings. Diagonal mesh is applied at reentrant corners. The corners of returns must have mesh applied so there are no unreinforced areas of base coat. Corners, joints, and grooves often require touchup and additional base coast application to assure full embedment of all mesh with no visible mesh ends or pattern.

Surfaces to receive sealant must be clean, sound surfaces without regularities, excess roughness, or thin spots.

Base Application – Medium and High Impact Exposure

For medium exposures, a second layer of mesh is applied over the first in a similar manner. A third application of base material is then applied so that no mesh pattern is visible and the minimum thickness is 1/8″ (3.2mm).

For high exposure, approximately 3/32″ of material is applied and a high impact mesh is troweled onto the face of the base material. After 24 hours of curing, a layer of standard weight mesh is applied as before. After curing, a third application of base materials is made with a total thickness of at least 5/32″ (4.0 mm). The high impact mesh has tightly butted joints.

Base Coat Primer

Priming base coats is often specified to enhance adhesion or to give better color control especially for bright or light colors. Primers are usually required on base coat surface at sealant joints.

Finish

No requirements other than the manufacturer’s except for a caution on the use of dark colors. Because of the low thermal mass of the base and finish coats (lamina) and their application over a thermal insulation, the surface temperatures of Wall Cladding can be quite high. Temperatures of 160 degrees F are common and 180 degrees F have been recorded. Dark colors absorb much more solar energy and should be avoided, because the high surface temperatures can cause problems.

 

Quality Control

By far the major cause of problems with exterior wall claddings today is poor workmanship. exterior wall claddings systems need to be installed correctly to perform properly. Exterior wall claddings need to be installed properly in order to perform properly as a key component of the building envelope.

After the repair, closely inspect the area for proper installation and good workmanship.  Create a punch list of any repair areas that need to be redone or corrected.  In particular inspect these areas:

  1. All terminations
  2. All areas requiring drainage from weeps
  3. All areas requiring sealants
  4. All pitch surfaces
  5. Any areas where flashing was installed.
  6. Look for uniformity or color texture and appearance.