I find your column in the Free Press most informative, and therefore bring you my problem.
Every year or so I have to repaint the cedar siding on my house because the filler I use to seal the cracks at adjoining boards peels off or cracks. In the past I have used glazing putty, wood filler and caulking compound to no avail. I would appreciate any recommendation to alleviate this situation.
This is a good time of year to address a question of this nature, as many homeowners prepare to paint the outside of their homes. Having to repaint wood siding every year or two is far too frequently and I will suggest some possible solutions to prevent this excessive chore.
The first thing you must realize is that wood siding is a natural product and is subject to changes due to seasonal fluctuations in the environment outside your home. Wood is a material that is particularly susceptible to shrinkage or expansion with changes in moisture content. This is especially true of open-pored woods like the cedar siding on your home. For this reason, wood siding is almost always treated with stain or paint to help maintain relatively even moisture content by preventing excess wetting and evaporation. Unfortunately, this paint or stain may not be a perfect solution, even with regular maintenance.
You have not been specific about the style of cedar siding on your home, and this may have a huge impact on the ability to seal the cracks prior to painting. If your home has older horizontal lap siding, then the cracks are likely at the ends of the boards. In this case, any older wood filler or putty should be scraped out prior to any further painting, as it will dry out and crack over time. An exterior paintable caulking with maximum flexibility should be use to fill the small gaps. This is one area where spending more will normally yield better results. Purchase the highest quality caulking you can that is specifically designed for exterior use and paintable. Silicone caulking and some other high quality caulking products are not easily painted and may be damaged by ultra violet radiation and are unsuitable for your purpose.
Once these vertical joints are caulked and cured, they can be repainted following the manufacturer’s instructions printed on the tubes. Some types may be recoated with finish paint only and others may require priming, along with any other bare spots of peeled paint on the siding. If the lap siding is installed in this manner and the caulking does not hold, then there may be another reason, which may be beyond repair.
Due their cellular structure, wood planks shrink little in their length. They do shrink considerably more in their width and thickness, as they dry out, after cutting. For this reason, horizontal siding that is butted end to end should have minimal gaps caused by shrinkage. The caulking and paint should be flexible enough to bridge the small separations at the ends of the boards. For this reason, you may be talking about a different type of siding, such as vertical or horizontal tongue and groove siding, which may be much more problematic.
Tongue and groove boards are joined along their length using a jointed tongue on one side that slides into a matching groove on the opposite side of the adjoining piece of siding. While this system normally works well due to the flexibility in the joint, it will be subject to much more shrinkage and expansion though the width of the boards than lap siding. This may be the reason for the cracking and popping of the filler you have put in these tongue and groove joints. In this case, these small gaps are not designed to be filled and it was a mistake to attempt this in the first place. Any loose filler should be removed and the boards repainted with attempts made not to bridge the cracks with too much paint. In this way, the boards with have subtle movements, which may lead to small visible cracks along the tongues, but this is nothing to worry about.
Whichever style of siding you have on your home there should not be excessive shrinkage or expansion after several years, as long as the siding has been finished properly in the first place. Unfortunately, it is common practice to install wood siding completely untreated and then finish it on the exterior face only. This can cause uneven shrinkage between the front and back face of the siding and often “cupping” of the boards. What it may also cause is the excessive cracking you are describing. If this is the cause of the problem, it may be very difficult to diagnose and will require complete removal of the siding to remedy, which is not practical. In this situation, the cracking is primarily cosmetic in nature and something you may have to live with until it is time to replace the siding.
