All Wet! Damp & Paint Problems


Editorial & Photography By: Dr. Christopher Cooper


A leaking gutter can destroy painted millwork in a matter of months, allowing rot to take hold in irreplaceable wooden millwork.

So, now that the nice weather is here it is time to start thinking about those outdoor damp-related paint repairs. If you are anything like me, you learn some lessons the hard way, for had it been properly maintained, there would be no need to repair peeling paint here and there around the house due to moisture problems. Unfortunately, there is one area that has been peeling for several years now and the wood underneath has been exposed to the elements ( I did a good job at ignoring it!!!) That is where the repair comes in. If it’s not dealt with this year, then the next words will be “replace wholesale”. No, thank you!

Do you remember that in school after you had misbehaved, the teacher made you write out lines: “I will not be late” or “I will not chew gum”? Well, I have one for you “I will not paint unless I have prepared the surface.” If surface preparation is not done properly, the area will need repainting soon again

A common mistake is doing only half a job at removing the peeling paint, then slopping on any old primer and paint, and not repairing the source of the moisture. This may be fine for a year or two; however, in most cases the paint will start to peel again and you will simply be wasting time and money as you will need to start all over again if the damp issue is not remedied. Using inferior quality products also will see you correcting the job in the very near future.

The Assessment. With a scraper in hand, assess the peeling paint to try to find out WHY it is peeling. Inspect to see if it is something obvious, an eavestrough not functioning properly, caulking gone bad, or leaking flashing.

In some cases historic siding can be damaged by excessive moisture penetrating from the interior of the home. For example, a bathroom or kitchen void of an exhaust fan will allow vapour to penetrate through the plaster or wallboard and further penetrate through the wood sheathing and clapboard, stopping abruptly on the backside of the exterior paint, creating moisture and the formation of a blister. A simple test to see if you have a moisture problem is to break open blisters and if bare wood is showing underneath you are sure to have a moisture problem.

At this point the only way to repair a moisture-related paint problem is to find and correct the source of the problem. Remember that a bi-annual inspection of caulking, eavestroughs and flashing must be done, once in the late spring and another just before the cold sets in (mid autumn). Also be sure to vent moist bathrooms and cooking areas to the exterior through a roof vent. And never hang wet clothing to dry in the interior of an old home. This has created rot and other much worse than blistering paint.

Some damp issues can be products of old-age. Oil based paints become brittle with time, lose their flexibility and develop tiny cracks and fissures as the surface expands and contracts over the seasons. These tiny cracks allow moisture in from wind-driven rain and snow. Damage occurs when that moisture freezes, or, on a hot day when moisture escapes as vapour, which will push the paint away from the surface. This damage is first seen as peeling or blistering paint, which progresses into a more serious breaking down of the wood underneath, eventually causing wet rot.

Where any moisture damaged wood has been exposed to the elements, even for a week, the wood must be sanded down to bright, clear wood. If not, the damaged or grey wood, when painted, will eventually separate from the sound wood below it. Most shallow areas where grey wood is being removed can simply be feathered in with the surrounding painted area. Deeper rot issues must be corrected by consolidation with wood epoxies (specifically formulated for exterior wood) or by using replication or Dutchman techniques.

After all the wood is repaired and all loose paint scraped away, sand the surface lightly to remove built-up dirt or any gloss from old paint. Make certain that you always wear a respirator to protect from airborne lead-based paint particles, be sure to place disposable drop cloths to catch chips, and be aware of wind conditions so as not to allow paint debris to invade your neighbours’ yards. And be sure to dispose of your lead-based paint responsibly by consulting with your local municipal government. Wipe down the sanded areas using a small amount of paint thinner, being sure to wear rubber gloves. The paint thinner will remove any dust and dirt left over and will allow you to see any imperfections prior to painting. Fill any voids or rough areas with a thin coat of exterior spackle and feather edges when dried. Now the area is ready for priming.

Check the weather! You do not want to do that final sanding just before it rains. Any bare wood will soak up the water like a sponge. If you paint over a surface containing moisture you will be back to square one. In fact make sure the weather has been good and dry . There is no point in painting if only a few days earlier it rained heavily. Also, if rain, high humidity, or cool temperatures are in the forecast, it is not wise to paint as such conditions will affect such things as adhesion and curing.

A beautiful example of well-maintained fretwork; however one must keep in mind that colour palettes should be well researched prior to painting. A Queen Anne such as this should mirror the vibrant colours available during the period.

Good preparation is the key to the success of any exterior paint project and most of the work involved in such a project is good old-fashioned elbow grease. Always use a traditional oil-based primer when working on exterior painted surfaces of bare wood. Your finish coat should be 100% Acrylic Latex. The Acrylic is a superior product that is flexible and can expand or contract with temperature and this will give more than 15 years of protection. And always remember that after all that expenditure of energy you don’t want to throw away all your hard work by using an inferior, CHEAP paint devoid of the elastic properties of a high quality paint which can survive in our harsh climate.


One Comment Add yours

  1. Robert J Carley says:

    Good article. One hundred and fifty year old wood – or older than that – always deserves every attempt at preservation. There is simply no comparison between wood milled from first growth lumber, to the wood available today.

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