Trenwyth / Acousta-Wal

Acousta-Wal Specifications

For the specifications of an individual product line, please see specific products pages for Astra-Glaze-SW+, Verastone, Trendstone.

Specifications: Printable : PDF / MS Word

Part 1 – General

Submit product literature, certifications, test reports and full size sample(s).

Quality Assurance
All sound-absorbing masonry units shall be Acousta-Wal units produced with special mold parts. Units shall be manufactured to meet ASTM C90. Production shall be monitored so that the top of the units shall be completely closed and edges of slots and ends of blocks shall be straight and clean. Type IV units shall have fillers inserted in the cavities at the block plant. Type IV fillers shall be fiberglass fillers laminated to metal septa. All filler material shall be cut accurately to size and installed as recommended for the type of Acousta-Wal units specified. All units contain an approved integral water repellent CMU admixture at the time of manufacture.

Fire Resistance: Define hourly ratings by NCMA TEK Notes.

Field Constructed Mock-ups: Construct a sample panel, no less than 4′ x 4′, of units of each color and size to be used in the project.

Order a full size unit to illustrate color and texture for approval. Northfield requires that a jobsite sample panel be installed at the jobsite prior to installations. This panel will represent both the quality of the product and the workmanship to be expected for the project. The panel must be approved by either the owner or architect for the project. Northfield will provide 4″ units for a 4′ by 4′ sample panel at no cost for the material (not including freight to site).

Acousta-Wal units shall be delivered to the jobsite on covered banded pallets with cardboard between layers. Store pallets in single-stacks on level ground and cover with waterproof covering (e.g., tarpaulins) to protect the blocks from inclement weather. Handle blocks carefully to avoid breakage and damage to the finished surfaces.

Protection of Work: Cover walls each day after installation to keep open walls protected and dry.

Part 2 Products

Grey Block / Acousta-Wal® concrete masonry units


Northfield Block Company
3400 East Bungalow Road
Morris, IL 60450

Colored matching or contrasting mortar is available. Consult NCMA TEK Notes, available at for mortar type and specifications. For all exterior mortar, use matching an approved water repellent mortar additive, following manufacturer’s instructions. Consult manufacturer for recommendations.

Acousta-Wal units surfaces are manufactured to provide finished dimensions of 7-5/8″ x 15-5/8″ ± 1/8″. Bed depth dimensions for single face units are 3-9/16″, 5-9/16″, 7-9/16″, 11-9/16″ ± 1/8″. Two face units are 3-1/2″, 5-1/2″, 7-1/2″, 11-1/2″ 1/8″. Please contact the plant for size availability.

Part 3 Execution

Draw blocks from more than one pallet at a time during installation. All exterior mortar shall include an approved water repellent additive added to each batch in the appropriate dosage rates for mortar type (M, S or N) per manufacturer’s instructions. Refer to NCMA TEK Notes, for Hot and Cold weather construction practices.

Acousta-Wal units shall be installed by the general contractor or masonry contractor. Installation of Acousta-Wal blocks shall be consistent with the best concrete masonry practices. Only quality units shall be used.

Acousta-Wal blocks shall be laid in running bond or stack bond as specified with the closed tops up. They shall be laid in a full horizontal bed of mortar. The slots shall face toward the room or area where sound absorption is required as shown on the plans. Slots shall be kept free of mortar and debris and the exposed mortar at the bottom of each slot shall be neatly tooled. NO RAKE JOINTS.

Lighting: Provide adequate lighting for masonry work by placing lighting at a reasonable distance from the wall for even illumination. Do not use trough lighting.

Cutting: Make all unit cuts, including those for bonding, holes, boxes, etc., with motor-driven masonry saws using either an abrasive or diamond blade. Cut neatly and locate for best appearance.

In all exterior mortar, we recommend using an approved water repellent additive following manufacturer’s instructions. Consult manufacturer for recommendations.

Install flashing at locations shown in the plans and in strict accordance with the details and the best masonry flashing practices.

Install weep holes and vents at proper intervals at courses above grade and at any water stops over windows, doors and beams. Consult NCMA TEK Notes, for proper flashing and drawings.

The ground face and filled and polished faces shall conform to the requirements of ASTM C90 when viewed from a distance of 20 feet at right angles to the wall with normal lighting.

The units must be laid in a full horizontal bed of mortar and laid with the closed tops up. The slots should face toward the noise source. Slots must be kept free of mortar. The exposed mortar at the bottom of each slot should be neatly tooled and all debris removed. NO RAKE JOINTS.

Under no circumstances should the units be laid upside down; that is, with the closed tops down. First, it would be impossible to lay the units in a full horizontal bed of mortar if they are laid upside down. Second, excess mortar would fall into the slots giving an unsightly appearance. If the cavity volume were reduced by more than 5 to 10% due to mortar falling inside, the acoustical performance of the units would be altered.

All concrete masonry units are manufactured with an integral water repellent. The admixture is mixed through the block at time of manufacture and lasts for the life of the product. Mortar must also be treated at the time of installation.