Cleaning & Restoration Tools and Gadgets / Restoration

Injection Drying: Inspect, Plan and Dry

March 3, 2014

As a 40-year veteran of the cleaning and restoration industries, I’m proud to have witnessed and been a part of the advancements in science and technology. Injection drying is one of these advancements that have improved restorers’ services and at the same time given our customers a better and healthier end result.

Remembering back over 30 years ago, we did not address the water and contaminants inside the walls very well, if even at all. The common practice was visual and wet check inspection - if the walls/ceilings were wet, we tried to assess whether or not they could be dried and repaired in place. If the damage appeared too great, then they were removed and replaced. I know that is not too different from today’s practice, but back then we were not thinking about inside the walls. We foolishly made the assumption that once the exterior of the wall was dry, everything behind it was dry or contained little enough moisture not to be a concern. Well, we all know better than that now and know of the danger to health and the structure by leaving wall cavities wet.

The goal of any water restoration project is to return the structure to a pre-loss condition. Modern equipment and techniques have helped contractors to actually dry materials in place, rather than demolition and replacement, and that is particularly true of wall and ceiling cavities.

Walls can be complicated to dry due to their varied and complex construction – including several layers or problematic materials. Inspection, as with all drying projects, should be thorough to unveil the potential challenges. Here are a few basic inspection tips:

  1. Find an outlet that can be removed to see the layers.
  2. Ask the owner, manager or building engineer.
  3. Be a little disruptive in an inconspicuous area – in a closet, behind cabinets, etc., or remove the baseboard. This might even include the use of a Borescope. Once you know the materials and how wet they are, you can make a plan of attack.

For this discussion we will assume that the inspection determined there was enough moisture inside the cavity to be concerned with, and that injection drying is the best option. As a side note, I would point out that some walls may need to be extracted if there is any contained-standing water. This is common with metal studs and framing. Extraction is usually best accomplished by drilling holes or removing wall slightly above the sill plate but below the baseboard top if possible, and applying vacuum/extraction to that area.

The simplest and least obtrusive way to dry inside a wall with injection is to remove the baseboard and drill the appropriate sized hole measured to the equipment you’ll be using. When removing the baseboard, be sure to use a razor knife to score the paint or sealants on top of the baseboard where it attaches to the wall (otherwise it may peal the paint) and then carefully pry it from the wall. Wet sheetrock can be very flimsy. A wide putty knife or scraper helps spread the pressure out over a larger area.

When drilling the holes for the tubes or nipples that will penetrate the wall, try to keep them above the sill plate but below the top of the baseboard so you’ll eliminate the need to repair the wall. If you’re successful doing this, you’ll be able to reattach the baseboard with little or no repair after drying is complete.

There are several different types of wall injection drying equipment and attachments on the market today, most are promoting a positive pressure system that pushes air into the cavity either with heat or simply at room temperature. The positive pressure system should be used when there are no known or suspected contaminates inside the cavity that could be forced into other areas of the structure. The positive pressure systems usually work best because they generate more airflow and more pressure that will cover a larger area with better penetration, giving you a faster dry. The negative pressure systems are to be used if any mold or other known contaminant is in the cavity. These are used by inserting the same tubes or nipples into the wall but reversing the air flow to pull air and moisture out of the wall. It is extremely important to note that these must be used with a water/vapor interceptor between the affected area and the vacuum unit. Also, use a HEPA filter on the exhaust of the unit to capture contaminates and keep them out of the surrounding environment.

So this brings up the question: Where does the air vapor go when you pressurize a wall cavity? Although I assume it’s possible, in 40 years experience I have never run into a completely air tight wall. The fact is that they breathe and are meant to be that way. When a wall cavity is injected and pressurized with air (preferably warm dry air) it seeks equilibrium and will follow the path of least resistance. It’s fair to say that it will go wherever it can.

If the air is heated it will rise until reaches neutral air pressure and temperature, meaning equilibrium where the vapor is suspended in the air. Most attics are well ventilated and air will escape easily from there. You can also expect a small amount of the air inside the cavity to escape through electrical outlets or along sill plates. This is normal and acceptable as long as there are no airborne contaminants (i.e. mold, asbestos and lead) escaping with it. If there is a large amount of moisture within the walls it may be necessary to create an air path through the wall by opening up an area above or opposite of where you are injecting. This can be done by drilling 1” holes or cutting small sections out where you want the vapor-laden air to escape.

One final tip I want to share that has been forgotten by many contractors, but is still very effective in drying heavily painted walls, is the use of a perforating rolling tool. This tool can be used on walls that are heavily saturated and that may have multiple layers of paint which inhibit drying. You simply roll the tool using pressure across the wall which will puncture the wall with hundreds of tiny breathable holes. This breaks the paint barrier just enough so the moisture can escape but does not damage the integrity of the wall. In most cases a light sanding and repainting will be all that is necessary to restore the wall.

When a wall can be dried and restored without demolition it should, but the point of all of this is not to forget the wall cavity. Failing to address it is not an option. There are too many health concerns and liability issues for you, so get the right tools for inspection and drying and solve the problem.


Author’s Note:

 A special thanks to Dave Hanks, Scott Warrington and Ron Colling who added their industry expertise to this article. 

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