Wall Spray “How-to-do-it!”

5Wall Spray is a combination of science and art. The science is finding the exact ratio of water pressure, amount of material, air pressure and material manufacturers. Weather temperatures and humidity also contribute to application of wall spray. Wall spray is also an art where you need to learn the best technique to properly and quickly fill the wall cavity. Sound difficult? Not really. The trick is to practice and be willing to adjust.

This article will attempt to help you be mindful of the initial settings and conditions to make the science and art of wall spray combine to make you an effective installer. The pictures demonstrate our CM2400 being used for wall spray. [1. Nearly all of our machines are capable of wall spray. Starting with the CM1500 (double-blower model) through our CM300, you can wall spray quickly and efficiently.

While this article will not answer every question about wall spray, it is a guide to starting. We offer on-site training.

Job Preparation

Since you will be recycling already sprayed, damp material back into the hopper, you MUST make sure that the floors are thoroughly clean. A nail can damage the airlock seals and reduce the needed PSI to perform Wall Spray. Besides, any garbage thrown into the machine will show up on the wall. Your customer will not be satisfied to see dust, building debris and junk mixed in the wall system.

Machine Settings

Depending on conditions (humidity/material) these settings are to be considered a starting point. The goal is to add as much water as necessary to cause the material to stick into the wall cavity. Oversaturating the material will cause it to fall out of the wall. Too little water and the material will simply bounce back out of the wall. Consider the following settings for beginning:

  • Water Pressure: Adjust water pump pressure to 350 p.s.i (#25015 tips)
  • Material Feed: Open the slide-gate setting to 2/3 open (‘locking pin’ in 8th hole open). Each hole is one inch.
  • Blower Speed: Turn both blowers to #4 or #5 on the blower control dial.

When the above settings are made, put two bags of cellulose into hopper. Spray approximately one bag to create a recycle slump. Return the slump back to the hopper (a large shovel and trash barrel). It may take a few wall cavities to obtain the right ratio of water, material feed and blower speed.

Holding and Using the Spray Nozzle

1Developing a consistent spray technique is not difficult. The goal is to fill a standard 2×4-8’ wall cavity in 30 seconds. Do not feel you need to rush as you will leave gaps of material. At first, you will have quite a bit of overspray. Since it can be recycled, overspray is easier and better to manage than fixing gaps later.

The Cool Machine spray nozzle has a teardrop shape. The teardrop is held upside down with the spray tips angling upwards. The upward spray pattern will lead the material and provide a moist surface as you spray up the wall.

Starting at the bottom of the cavity, aim the spray nozzle into one of the lower corners of the cavity and spray into the opposite corner. Then direct the spray nozzle into the cavity, parallel to the floor. You should be able to stand 18” from the wall.

In fluid, 1-second intervals, sweep the nozzle back and forth to fill the cavity.

The more consistent spray rhythm you develop, the better the material will fill the cavity and the overspray will become less.

When you reach the top of the wall cavity, spray into the corners, moving slightly closer. This will help you minimize gaping at the top of the wall cavity.

Recycling Material

The hopper loader will mix the material into the machine in a ratio of about 2 parts dry to one part recycle. When adding the damp material, stir it with your hand to help blend the material. Do not read deep into the machine.

Your goal is to create a consistent blend of damp-to-dry. As the job progresses, you may need to increase water pressure or lower the material feed.

Scrubbing Material

4When a number of runs have been filled, scrub the material off the wall. We suggest that you scrub the wall with every 10’ section of new spray. Holding the scrubber with a slight angle, run it up each cavity, overlapping the studs.

Finishing the Job

When you have finished spraying the job, inspect each run to make sure that any gaps or pockets are refilled. We recommend quickly over-spraying, with water only, the final surface. This will create a nice crust.

Instructions for Your Contractor

Because you are adding water to cellulose, the wall spray must be allowed to dry. The fiber moisture should not exceed 35% moisture content. Depending on the thickness of the wall, 2-3 days is typically sufficient. Do not cover walls with plastic and avoid oil based paints on the drywall (gypsum board) inner walls. The walls need to ‘breath’ or allow moisture migration.