.png?width=387&height=144&name=MPI%20logo_4C-WHT_150%20ppi%20(1).png "MPI logo_4C-WHT_150 ppi (1)")
When planning a repaint project, it’s crucial to thoroughly assess the condition of the existing coating and substrate. This evaluation not only involves identifying surface defects but also understanding their severity to determine the necessary surface preparation and priming. By following a systematic approach, including the use of MPI’s Degree of Substrate Degradation (DSD) system, professionals can accurately forecast the required labor and materials, ensuring a successful outcome for any repaint project.
When planning a repaint project, assessing the condition of the existing coating and substrate is the first and most important step to ensuring a successful repaint project. This is because the state of the existing coating will usually dictate the type and amount of surface preparation and priming required. Evaluating the condition of the existing coating should not be confused with simply identifying the types of surface defects and failures present. Although recognizing the types of defects and failures is an important aspect of the evaluation stage, it is really only a portion of the assessment process.
To understand the whole scope of the project at hand, and to be better equipped to forecast the extent of labor and materials required; the severity of surface failure and defects on the existing coating must be determined. Below are 3 steps that are crucial to the success of planning any repaint project:
- Determine the type of substrate/coating being repainted. Different substrates have different properties and determines which defects to look for when assessing the state of the existing coating (ex. Wood substrates are prone to sap bleeding whereas concrete substrates are prone to efflorescence). Additionally the type of substrate and existing coating will often determine the type of primer required (if any).
- Determine the Types of Defects/Failures present. Identifying the types of defects present may help determine the source of the existing system’s failure (ex. Erosion is usually the result of natural weathering over time whereas flaking is commonly caused by poor adhesion between coats and thermal change stress). This step helps to narrow the focus regarding the root cause of defects and thus provides the framework for how to remedy the problem.
- Determine Severity of Defects/Failures. This is one of the more difficult steps to identify as it takes into account the severity of each surface defect present on the existing coating. The importance of this step cannot be overlooked as this aspect of assessment has the greatest potential to influence the budget of the project. While Step 1 above determines the type primer required, and Step 2 provides the framework for how to remedy the problem, this step determines not only the type, but the amount of surface preparation and priming required (see MPI Maintenance Repaint Manual for Repaint Surface Preparation Standards). For example after a specifier determines that blistering, efflorescence and peeling is present on an exterior concrete wall coated with a latex system, the specifier must now evaluate the extent of these defects. Is the blistering slight or severe? Are pieces of paint peeling down to the surface or just the intermediate coat? The answers to these questions leads to the specifier’s decision of whether the surface requires a “touch-up”, spot priming or complete removal of the existing coating followed by a full coat of primer to ensure the substrate can be successfully repaint.
Degree of Substrate Degradation
The Degree of Substrate Degradation (DSD) is a system that was developed to simplify the last step of the process listed above. The DSD system categorizes all existing surface conditions into 5 DSD levels with a DSD – 0 being an essentially ideal surface for repainting and a DSD – 4 being a surface that is badly damaged and requires structural repair. A more detailed explanation of the DSD system is described below:
|
DSD – 0 |
This is an essentially “sound” surface. It may have visual defects, but the film is still protective. It may simply need a color, sheen, or other change. |
|
DSD – 1 |
This is a “slight” degree of surface degradation. It is unlikely that the topcoat has been anything but insignificantly breached, and in no case is the substrate exposed. Surface preparation requirements should be “slight’ and only “touch up” with the top or intermediate coat should, in most cases, be necessary. |
|
DSD – 2 |
This is a “moderate” degree of surface degradation. Damage to the film integrity is such that “spot priming” should, in most cases, be adequate after moderate surface preparation requirements. |
|
DSD – 3 |
This is a “severe” degree of surface degradation. Damage to the coating is widespread. Necessary surface preparation will likely be substantial, and a full coat of the appropriate primer is to be expected. |
|
DSD – 4 |
This is an essentially “unsound” surface. Repainting of this surface is unwise (except in cases where a temporary cosmetic remedy is deemed acceptable under the circumstances) as the substrate needs repair (i.e. beyond standard painting surface preparation), or replacement, before the appropriate coating system. |
Using the DSD system with the example posed above in Step 3, if the blistering is slight and there is a moderate amount of paint peeling down to the bare substrate, then the project would be a DSD – 2 and would require the surface to be cleaned with troubled areas spot primed. If the blistering and peeling is severe, then the existing coating must be removed entirely and the whole surface would need to be primed and then topcoated.
Exterior Concrete DSD Example:
|
Moderate to Severe |
|||
|
Oils/Grease |
Any |
Any |
Any |
|
Rust Stains |
Slight (surface) |
Slight to Moderate |
Moderate to Severe |
|
Sagging |
Slight to Moderate |
Slight to Moderate |
Moderate to Severe |
*Flaking/Peeling (1) – Flaking or peeling between topcoat(s) and intermediate or primer. Primer remains intact on surface
*Flaking/Peeling (2) – Flaking or peeling down to substrate. Primer removed from the surface.
Assessing the condition of an existing surface is necessary to the success of any repaint project, yet often this process ends once the types of defects and failures are identified and the next process of specifying systems begins. Planning a repaint project in this manner is not a good practice as the specifier is essentially basing their selection of a paint system off of an incomplete evaluation of the existing surface’s condition.
Consider a doctor that determines a patient’s arm is broken. The doctor still cannot properly recommend treatment for the patient until the severity of the break is established. Depending on the extent of the injury, the patient may require surgery and a cast for several months if the arm is severely broken, or may just need to rest for a few weeks if the break is just a hairline fracture. If the severity of the injury is not established, the treatment prescribed by the doctor is essentially a guess and runs the risk of over/under treating the issue at hand. Likewise for someone writing the specifications for a repaint job, they cannot specify the amount or type of preparation required for a repaint project until they can adequately assess the type and severity of defects afflicting the existing coating.
