Painting Wood Doors
In commercial or institutional buildings, doors arguably experience more traffic and abuse than any other surface except the floor. The type of doors predominately used in these buildings are “fire-rated” doors. They’re solid with a skin of birch, maple, mahogany or oak and may be finished with stain, varnish or paint.
Here are a few tips to assure a more successful project.
It is critical to seal the top and the bottom edge, and if there is any possible exposure to water vapor or moisture, all six sides of the door should be sealed well. This prevents the door from changing dimensionally.
Also, it’s important to get this sequence right: specify that door tops, bottoms, and edges be coated with the specified system after doors are sized and shaved to fit the frame, not before!
It is common to see doors and frames arrive on-site already primed; however, this white primer is almost always of a type unknown to the painter or specifier and is often of questionable quality. MPI has observed problems with factory-primed doors including poor adhesion, overly thin film thickness, and poor hide.
Some steps to help assure success:
• if the primer is flat/low sheen and a little rough, it is likely porous, which creates problems including raising of the wood fibers (and with composite wood doors, “fiber-popping”) if a waterbased finish is applied. Start with one door as a test: lightly sand the primer, apply the waterbased finish, and check the next day to see if the fibers are raised. If so, ask the specifier to allow application of a quick dry oil, alkyd, or other solvent-based primer prior to topcoating.
• if the primer is shiny and smooth like glass (often the case with U/V cure factory primers) the topcoat may not adhere and peeling/delamination failure can occur. Two possible solutions include:
- sand the gloss off with a power sander (palm or orbital sander) using 150-180 grit sandpaper.
- dull the surface and then apply a bonding primer (a waterbased product may suffice). Again, try one door first. Apply the primer and topcoat (a “high performance” latex is recommended). After the finish coat has cured, do an adhesion test to verify proper adhesion to the surface.
— Excerpted from MPI’s online Architectural Coatings Specialist training course
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Tips for Specifying Interior Latex:
Good, Best, Low Odor/VOC...
All latex paints are not created equal. With the wide range of resin and additive technologies available today, performance and application characteristics (as well as price points) will range all over the board.
MPI paint standards and systems are designed to help architects, specifiers, property managers, and contractors choose the right system for each project by classifying these products into reasonable divisions of performance. Here’s an example using interior latex.
1. “Conventional” latex. These standards are named “Latex, Interior” followed by their gloss level, and occupy MPI #s 53, 44, 52, 43, 54, and 114. Products approved under these standards have passed requirements for dry time, consistency, hiding power, reflectance, alkali resistance, burnish resistance, scrubbability, flexibility, etc. They offer standard performance suitable for residential and “light use” areas in commercial applications such as offices and meeting rooms.
2. High Performance Architectural Latex, MPI #s 138 through 141. These are our most rigorous standards for interior latex — what most people call “best.” Products approved in these categories passed the tests above, but endured far more scrub cycles than “Conventional” latex, and also met stringent requirements for cleansability, resistance to staining, marking, and burnishing. These systems provide almost equivalent performance to alkyds but without the odor and VOC, and are better suited for commercial and institutional uses such as schools, public buildings, hospitals, etc.
as well as high-traffic areas like doors.
3. Virtually Zero VOC Latex: These standards are named “Latex, Interior, Institutional Low Odor/VOC” and are MPI #s 143 through 148. Giving these products their own category makes it easy for buyers and specifiers to find high quality paints with exceedingly low odor and low VOC (under 10 g/l). Products that pass this standard meet much higher requirements than the Conventional Latex categories, and slightly lower than the High Performance category. These paints are suited for projects when both performance and minimal environmental impact are required, or for projects that require extremely low odor while painting.
And depending on the exposure environment, one of MPI’s other standards for interior waterborne finishes may be more appropriate -- for example, MPI#151-154 “Light Industrial Coating, Interior” offers mild chemical and corrosion resistance; “Epoxy-Modified Latex” (MPI#115) is a two-component paint with some epoxy toughness in a latex formula; or “Waterborne Alkyd” (MPI #157-171). Click here to see the full list of MPI paint types and current Approved Products for each.
Revisions to MPI Standards
MPI#108 Epoxy, High Build, Low Gloss: changes were made to paragraph 1.2 to eliminate the requirement that the supplier must also have a product approved under MPI # 101 as part of the system.
Click here to purchase the revised standard.
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