THOUGHTS ON PRE-PRIMING OF SIDING, WINDOWS AND DOORS
Since our founding in 1987, Fine Paints of Europe has always advocated the tried and true traditional method of priming exterior wood on all “six sides” prior to painting and/or installation. THE ONLY PRIMER SUITABLE FOR THIS PURPOSE IS A HIGH QUALITY ALKYD PRIMER SUCH AS THE OIL PRIMER OFFERED BY FINE PAINTS OF EUROPE. Fine Paints of Europe Oil Primer is currently relied upon by numerous manufactures and restorers of high quality windows and doors who encapsulate their products with Oil Primer before painting and/or shipping.
The use of an Oil Primer on wood at proper moisture levels assures:
- A barrier coating which will not allow moisture penetration in or out of the wood. This promotes dimensional stability and prevents moisture from any source (including interior moisture) from penetrating the wood and causing paint failure.
- An ideal substrate for all subsequent coatings whether they be waterborne or solventborne, alkyd or acrylic.
- Properly primed wood will not be damaged by UV light. Most homeowners and contractors are unaware that if exposed to direct sunlight for as little as two weeks unprimed wood will lose a significant amount of the hair-like lignin which allows a coating to adhere. Once lignin damage occurs, it cannot be corrected and the ability of the wood to “hold paint” will be significantly reduced for its lifetime.
WE NOTE THAT ALMOST ALL COMMERCIAL WINDOW MANUFACTURERS AND LUMBER MILLS OFFERING PRE-PRIMING EMPLOY WATERBORNE PRIMERS BECAUSE THESE COATINGS ARE INEXPENSIVE AND THEY DRY VERY QUICKLY – NOT BECAUSE THESE PRIMERS ARE SUITABLE FOR THE TASK. The use of these substandard waterborne primers also enables the quality of the wood itself to be concealed from both contractor and homeowner. Low quality finger-jointed wood is easily concealed with an inexpensive waterborne primer. WE FIND IT SOMEWHAT CURIOUS THAT MANY WINDOW MANUFACTURERS REFUSE TO SELL UNPRIMED WINDOWS SIMPLY BECAUSE THE QUALITY OF THE MATERIALS AND WORKMANSHIP WILL BE REVEALED. Personal experience indicates that you get a much better quality window or door if you purchase it unprimed than if you get one pre-primed.
1. Clients purchasing premium custom windows and doors pay an average of $3000 per window and $5000 per door. Work of this quality comes from custom shops whose goal is to produce a one hundred year window. Such shops know how to do it right and typically work with exotic species such as mahogany. Custom shops seldom release a product without oil priming as they are dealing with demanding and unforgiving clients. Owners of custom shops realize that an investment of $10 to $15 per window in Oil Primer will serve to protect their reputation no matter what goes wrong on the job site. They are also aware that oily exotic woods do not accept waterborne primers well and that adhesion is far superior with a solventborne alkyd primer. Many of America’s high quality custom shops have been using Fine Paints Oil Primer for fifteen years or more.
2. Most American homeowners are unwilling to invest in premium windows and therefore purchase well made pine windows from large manufacturers who prefer to pre-prime for reasons mentioned earlier – these windows typically cost between $1000 and $1200 each. Homeowners and their contractors who insist will discover that domestic manufacturers of medium priced windows will supply windows in raw, unprimed condition as special orders. This enables the client to properly prime bare wood with an Oil Primer and then finish the window with Hollandlac or ECO before installation. Typically, the second, final coat of paint is applied to both the interior and exterior of the window after installation. Experience indicates that a pine window which is properly primed and encapsulated will yield fifty or more years service. That same window primed with waterborne primer and finished with waterborne coating will seldom yield more than 20 years service and the client will be repainting every few years. If the window is properly primed the client should be receiving twelve to fifteen years out of each repaint. Clients who have already purchased pre-primed windows are advised to aggressively sand the primer through to bare wood before re-priming with Fine Paints Oil Primer – special care should be taken to avoid scratching glass.
3. Siding and shingles: In no other exterior application is the use of Oil Primer more important than wood siding. In this instance Fine Paints recommends that western red cedar or eastern white cedar be specified (no pine or spruce) and that each piece of clapboard or shingle be encapsulated with Oil Primer or ECO primer and receive one coat of ECO on both sides prior to being nailed in place with stainless steel nails. IT IS IMPERATIVE THAT CARPENTERS INSTALLING SIDING HAVE AVAILABLE THE SAME PRIMER USED FOR PRIMING PURPOSES IN ORDER TO HEAVILY PRIME END CUTS BEFORE NAILING IN PLACE. End cuts are the most likely means by which moisture will penetrate exterior siding and a small opening on one end of a clapboard can easily result in total paint failure on that clap in a matter of months as moisture migrates horizontally by capillary action.
Clients working on siding and shingles must be sensitive to the risk associated with having alkyd primed or painted wood come in contact with other alkyd primed or painted wood – THE PIECES OF WOOD WILL BOND TOGETHER AS IF UNDER THE INFLUENCE OF SUPER GLUE. Alkyd coatings takes several weeks to cure and two pieces of alkyd primed siding can bond together ninety days after priming if not separated by furring strips, shims or other means. This risk identifies one more reason why it is impractical if not impossible to properly prime siding with an Oil Primer in a factory environment. Thus, siding should always be delivered raw to the job site and placed in a shady area or covered with black plastic before priming in order to prevent UV damage and the risk of picking up moisture. Siding should be purchased and tested upon delivery to meet a 12% or less moisture spec.
Interesting historical context – until 1903, carpenters in the United States regularly worked with primers – they would not consider nailing a piece of exterior wood in place without first priming it on all six sides with a primitive oil primer which served as a permanent moisture barrier. As a result of a early labor conflict between carpenters and painters in 1903 it was informally agreed that carpenters would no longer involve themselves in application of coatings and the important step of oil encapsulation was largely abandoned. It is estimated that less than 2% or new residential construction in America today enjoys the benefits of back priming and encapsulation. Our experience over the course of the last twenty four years indicates that unless the homeowner insists upon this critical but unseen step, back priming will not take place.
Remember back priming with a porous, waterborne finish accomplishes nothing. Waterborne paints with the exception of waterborne alkyds such as ECO have a high perm rate and offer no protection.