Veneer Wall: Concrete Block Veneer/Steel Stud Framing

• Multi-family residential, hotels and office buildings, shopping centers and restaurants
• Use where budgets are more important than longevity

• Has the appearance of a solid masonry building but steel framing is typically less expensive than a concrete block (CMU) back-up wall
• Lighter weight than masonry veneer on CMU back-up
• Durable, long-lasting wall system
• Minimal long-term maintenance
• Great design flexibility with many colors, textures and bond patterns available
• Cavity system keeps building interiors dry

• Steel stud back-up wall will flex more than the veneer will. This can lead to cracks in the veneer unless the back-up is designed to strict deflection tolerances.
• Concrete block shrinks as it ages. It needs control joints at 24’-0” on center, max.
• Multiple trades involved with this wall system which can make jobsite coordination more difficult.
• Tolerances for steel erection are looser than those for masonry. This can lead to conflicts during veneer construction. Include a larger air space in the cavity to accommodate this.
• Steel studs can corrode if water penetrates past the drainage cavity or if moisture condenses on the steel.
• Interior drywall surfaces are less robust than CMU walls. This can lead to vandalism and damage in heavy traffic areas.
• There is a potential for mold growth on the sheathing of the cavity unless you use mold-resistant sheathing.

• Backup: 16-gauge x 6” steel studs at 16” on center
• Veneer: 4” concrete block (CMU), 4” x 8” x 16” (nominal)
• Sheathing: 5/8” exterior grade Type X gypsum sheathing, screwed to the studs
• Weather Resistive Barrier: Building wrap with 6” overlap where sheets meet
• Cavity: 2-inch air space
• Insulation: 5.5-inch batt insulation installed between the studs plus 1-inch rigid extruded polystyrene insulation in the drainage cavity (Reference: Colorado Masonry Systems Design Guide, Chapter 8, figure 8-17 (similar))
• Flashing: Self-adhered bitumen flashing paired with metal drip edge (Reference: Colorado Masonry Systems Design Guide, Chapter 6, Shelf Angle Flashing Options, Fig.6-3 (Option 2))
• Masonry Ties: Two-piece adjustable ties screwed into the studs that are rigid horizontally and can slip vertically, spaced at 16” (horizontal) x 16” (vertical) (Reference: Colorado Masonry Systems Design Guide, Chapter 6, Table 6-4)
• Shelf Angle: To support veneer at floor level (if building is more than 30 feet tall).
• Mortar: Type N, Portland cement/lime, plain gray
• Joints: Concave tooled

• In areas with high seismic risk, masonry ties and anchors might have special requirements. Check your local building codes.
• In Colorado, lightweight CMU is the norm. In other parts of the country, medium weight and normal weight block is more common.

• Fire Rating of a multi-layered cavity wall = (Rating₁ ^0.59 + Rating₂ ^0.59 + 0.3)^1.7
• The concrete block veneer alone has 1-hour fire resistance
• If you need more fire resistance, add layers of Type X gypsum board to the steel studs in the structural back-up wall.

Reference: NCMA TEK Manual 07-01D

• 32.71 pounds per square foot

• STC = (weight of wall)^0.233 x 21.5
• STC = 48.46 dB

Reference: NCMA TEK Note 13-01C

• R-value: 30.68
• Calculations
  • Outside air film                                          0.17
  • Lightweight CMU veneer                          3.86
  • Air gap                                                         0.97
  • 1” extruded polystyrene                           5.00
  • Gypsum sheathing                                    0.45
  • 5.5” batt insulation                                  19.00
  • Interior air film                                           0.78
  • TOTAL                                                        17.68

• There are three different pathways to meeting the requirements of the International Energy Conservation Code (IECC). You can use R-values to satisfy the prescriptive limits of Table C402.1.3 of the code. Using R-values requires continuous insulation in the cavity in all Colorado climate zones. Following Table C402.1.4 of the code uses U-values to meet the insulation requirements. This approach does not require continuous insulation in the cavity. A third approach is to use computer software like COMCheck — to prove that the building meets code. Computer software is the most complex, but it is also the most flexible option. It is often the best choice for mass walls.
• CMU shrinks as it ages. Install horizontal reinforcing @ 16” on center, vertically to control shrinkage cracking (even in a veneer).
• Use galvanized hardware and screws to attach veneer ties to the studs. This will minimize potential for corrosion.
• Tighten up the tolerances for steel construction to match those for the brick veneer. There can be significant conflicts between the steel erection and the masonry trades.
• Attach windows and doors to the structural steel studs, NOT to the masonry veneer.
• Make sure you have at least ¾” overlap between the door and window jambs and the CMU veneer. Install backer rod and sealant at the joints where different materials meet.
• You must use sheathing to face the steel stud wall at the drainage cavity.
• Use building wrap to cover the sheathing or use water resistant sheathing with taped joints.
• Design the steel stud back-up to a deflection limit of L/720 to minimize veneer cracking.
• Shelf angles may not be required for veneer support at every floor line. Cut down on the number of shelf angles to save money and simplify construction. If your CMU veneer is less than 30’ above the top of the foundation, it might not need relieving angles at all.

• Meet with the general contractor early in the project to make sure the steel erector understands how tight the masonry installation tolerances are.
• Anchor the veneer ties to the steel studs using galvanized screws. It is not permitted to anchor the ties into the sheathing alone.
• Uses two-piece adjustable ties that can slip vertically but are rigid horizontally.

Flashing

Self-Adhered Flexible Flashing: This tough, flexible flashing strip comes with a removable release liner for easier installation. The liner MUST be removed to allow the sticky layer of the flashing to self-heal around any punctures from nails or screws. If the sticky layer of the flashing is bitumen, hold this flashing at least ½” from the edge of the masonry so that the tar layer does not melt and form ugly black drips on the face of the wall. Bitumen-based flashing is often paired with a metal drip edge which can be exposed to sunlight. This flashing will stick to masonry, concrete, gypsum, wood, or steel.

Base of Wall —Flash Vent Self-Adhering SS Flashing with Drip Edge 

Roof to Wall Parapet Detail —York 304 SA Self-Adhering Stainless Steel Flashing (view from face of wall)

Roof to Wall Parapet Detail —York 304 SA Self-Adhering Stainless Steel Flashing (view from roof)

Masonry Anchors & Ties

Barrel Veneer Ties: Designed to minimize thermal transfer. The thickness of the barrel resists bending, and the single screw allows the anchors to be installed quickly. The factory-installed EPDM washers seal the penetration the screw makes in the air/vapor barrier. Using this style of masonry anchor will minimize the amount of tape used to seal joints in the rigid insulation.

H-B 2-Seal™ Thermal Wing Nut Anchor
Double-Pin Stone Anchor: Allows you to tie two capstones to the top of the parapet with each anchor. Drill an over-sized hole in the ends of each piece of the masonry cap. Insert a pin into the fresh mortar and then attach the angle of the anchor to the top edge of the structural wall.

H-B Stone Anchor #433

Cap with Pins

Weld-On Masonry Anchor: A masonry anchor that’s designed to be welded to structural steel members.

H-B Weld-on Ties