Have some wooden window sills with some decent size (rotted out) holes in them on the outside portions.
a. One Contractor wants to cut them off, flush, on outside and just screw in a new sill piece. Says that replacing the complete whole sill as a single piece is a "big job".
Is this just screwing in a wooden replacement piece for the outside a good approach ? Or,...?
b. If I try to plug up and fill the holes myself, sand smooth, and then re-paint them, what product should I use ?
Wood rot is like an infection. You can fill in the holes, but the rot will continue to eat the remaining wood. There may be treatments available that will kill or neutralize the rot. I've read that diluted ethylene glycol, used in some auto antifreeze, is effective.
The contractor is probably right about replacing the entire sill being a big job. His suggestion is somewhat equivalent to your idea of filling in the holes, but may be the easiest approach unless the rot extends deeper than you think.
When I had a similar problem with a seldom used door, one carpenter recommended digging out the rot and using Minwax "High Performance Wood Filler". It appears to be a kind of epoxy, and must be mixed with a liquid hardener before use. (Another suggestion was to use Bondo.)
In my case I waited too long, and the bottom of the door fell off! I opted to replace the entire door as part of a major renovation.
I've done all the methods you list, depending on the situation. Replacing the sill is a big job, as it's under the window, and usually part of the window. So that means removing interior and exterior trim as part of the job.
If the rotted spots are contained you can clean them out and fill with Bondo automotive filler. Then prime with linseed oil primer and repaint. (Water base paints will not hold up on sills. If you use water base trim paint you can still at least use a good oil primer.)
If the rot is on the outside it's often feasible to cut off the outer 1-2 inches and replace it. You just need to match the pitch and size of the existing wood. Also, use fir. Pine will rot quickly in that usage. And be sure the joint is good. You don't want water getting in there.
If the sill is very bad, and your finances are limited, and you don't care much about appearance with that particular window, another option is to do what you can with the sill and perhaps soak it with linseed oil to protect it in the future, then put a piece of sheet aluminum over it so that no more water gets in. Ugly, but it works.
The final option would be to replace the sill(s). In that case you'd want to do it when you're repainting either inside or outside, if possible.
first remove ALL the loose and soft stuff, then use dry rot liquid compound. It seeps into the soft wood and cures pretty hard on its own. Then use the epoxy compound to fill out flush, be sure to sand as soon as possible gets HARDER with time.
I actually reconstituted missing corners freom some antique windows. where there was nothing left but the paint surface.
I prolonged the life of my windows pulling rotten sills and replacing with pressure treated lumber. Got over 30 years with most of my windows. Eventually had to replace all my windows and did not use wood.
Fred: Don't tell people stuff like that because it only creates worry and confusion, especially if they're new to home ownership and don't know who or what to believe.
Bob:
As long as water isn't getting into the wood, the wood rot should stop and the wood rot fungus (latin name: Serpula Lacrymans) will go dormant for a few years and then die. So, even if you covered that whole window with a shower curtain from the outside to keep it dry, the wood rot would stop.
You can kill the wood rot fungus by simply removing any rotted wood and painting wood end cut preservative onto what's left. Wood end cut preservative contains the active ingredient copper naphthalene. It is the copper in copper naphthalene that is a natural biocide. There are other natural biocides including zinc, boron and arsenic. Zinc oxide, for example is used as the white pigment in many EXTERIOR paints because the zinc naturally keeps any shaded areas on the side of a house free of mold growth. The zinc kills the mold spores before they have a chance to grow and affect the appearance of the paint. Boron based wood preservatives are popular in log homes and for protecting telephone poles because the borates are highly soluble in water and gradually penetrate throughout the entire cross section of the wood logs or poles.
If you paint copper naphthalene onto the surface of wood that is in the process of rotting, the copper will kill all of the wood rot fungus it comes into contact with. The copper will also prevent the wood rot fungus from growing in any wood that has copper naphthalene in it.
You can buy end cut preservatives for wood which will typically contain about 12 percent copper naphthelene. That percentage goes up to about 24% if you buy an end cut preservative for the wood used for pressure treated wood foundations for houses. Since that wood will be underground all the time, it needs more protection. You can also go to any feed lot, horse stables or veteranarian and buy a copper naphthalene based treatment for a condition known as "Thrush" in horse hooves. Thrush is caused by a fungal infection, and the copper in copper naphthalene kills that kind of fungus too. Thrush treatment for horse hooves will typically be 37.5 percent copper naphthalene, which is much higher than you can get in any wood end cut preservative.
Also, if you have some end cut preservative available to you, you can build up the copper naphthalene content in the wood by applying multiple coats. The trick is to allow sufficient time for the solvent thinners in the end cut preservative to evaporate from the wood before applying another coat. Each time the wood dries out and you paint more end cut preservative on, you increase the amount of copper naphthalene remaining in the wood, thereby providing greater and greater protection against wood rot taking hold in that wood again.
You should also know that wood absorbs liquids and allows them to evaporate from the wood 15 times as fast at the end grain of the wood than across the wood grain. So, whenever treating any wood with end cut preservative or wood deck sealer, it's most important to apply plenty of product to the end grain at the ends of the boards.
If it were me, I would be inclined to replace the whole window with a new PVC window. That way, you don't have to worry about wood rot at all. That will give you a maintenance free window so that you only have to check that the caulk is in good condiiton. Also, it adds to the value of your house because any potential buyers is going to benefit from that window having been replaced with PVC.
Regardless of what you do, caulk your repaired or replaced window with a caulk known as Kop-R-Lastic. Any place listed under Caulk and Caulking Supplies listed in your yellow pages phone directory will be able to order Kop-R-Lastic for you. Kop-R-Lastic is a synthetic rubber caulk whose cohesive strength is even higher than it's adhesive strength, which means it sticks to itself even better than it sticks to common building materials. That means, if you ever need to replace the caulk around your window, you simply get one end of the Kop-R-Lastic loose and it pulls of the window like a rubber rope. I own a small apartment block with 66 windows, and I won't use anything but Kop-R-Lastic on them. Also, it's best to opt for the clear Kop-R-Lastic instead of any coloured Kop-R-Lastic because the colour comes from tiny coloured particles (called "pigments") that are added to the clear Kop-R-Lastic caulk, and those pigments lessen both the cohesive and adhesive strength of the cured caulk. Kop-R-Lastic is now manufactured in the USA under licence from the Koppers Company of Australia by the Henry Company of the USA.
I had three rotted window sills replace prior to having the house painted. Same fellow did the replacement. He did it from the outside--didn't touch or damage anything on the inside; that is, didn't remove the inside trim and didn't remove the window sill. Used a sawsall (????), went along underneath the sill cutting all the nails. Slipped in the replacement and nailed in place without disturbing the sill. I didn't think it could be done but he did it without a problem. Not wanting to disturb the inside finish I initially suggested going the route of cutting flush and screwing on a replacement piece. He scoffed at the idea and said let's do it the right way. Came out great! MLD
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