“Mahogany” Window Sill Repair

This is the condition of the pine trim repair after just a few years.

Many of our customers in Rollinsford, Portsmouth, Rye, Newcastle, and Rye Beach, NH, and South Berwick, ME have gorgeous historic homes. Some of these clients are open to the idea of pvc trim replacement for rot prone areas and some would prefer to stick with good old fashioned wood. What’s our official Meticulous position when asked if

The building envelope was well done. My predecessor had used a self adhering and self sealing membrane to keep the water from getting into the house. This is also what the bead of caulking looked like before we screwed the new sill nosing into place.

we prefer to use wood or pvc? Our answer is a resounding “Yes.” We would prefer to use wood or pvc, as opposed to…I don’t know, cardboard.

We can’t escape the understanding that there are many benefits of using pvc to replace rotten exterior trim. We also understand that today’s pine is absolutely NOT an option for longevity. But using pvc trim will never be the same experience, for a carpenter, as working with wood.

This is the profile of the new nosing. The rear notch at the top edge is to account for fitting around a lip on the window unit. The notch on the bottom rear edge is to fit over the siding, properly overlapping. The middle groove on the bottom edge is called a rain drip. This is to create an edge for the water to drip from before traveling further back to the siding.

We recently consulted with a great do it yourself homeowner in historic South Portsmouth, NH. Not long ago, he had replaced window sill nosings on the east face of his home that takes a brutal beating from mother nature, being only a couple dozen yards from the river. The work he did was with pine, unfortunately, so it didn’t take long to rot again. He wanted to stay away from pvc and asked what else we could offer. I suggested the solid but pricey “Mahogany.” I wrap this in quotations because I actually purchased a product called Red Meranti at Selectwood in Portsmouth. The way that I understand it, Red Meranti is not actual Mahogany, although is commonly referred to as Mahogany. Actual Mahogany is increasingly rare due to the strict forestry controls put in place after decades of over-harvesting in South America. Red Meranti hails primarily from Indonesia and Malaysia and is a nice solid, stable, insect and decay resistant choice for a sill nosing application, not to mention dense enough to not absorb tons of water. People often ask about cedar. I stay away from cedar in this application because cedar is a very soft wood and has an open grain structure. In my opinion, cedar readily absorbs water, even though it has the ability to resist rotting better than many species. Red cedar is much easier to work with because it’s lighter and softer and thus doesn’t require pre-drilling, but because sill nosings take a beating, I think Red Meranti’s density and close grain structure make it a superior choice.

Small trim screws through the face for holding power. There IS clear primer on this before installation, and notice the intentional bead of caulking to bond the trim to the bottom edge of the window.

In this instance, we were working on a wall system that was already well waterproofed. All we had to do was focus on doing the carpentry repair in a manner to stand the test of time… and the elements. Once we had test fitted the sill nosings to be splendid, we opted to use a higher-end primer that does a nice job of blocking the tannins from the Meranti from bleeding through the paint down the road. We chose to use a product called Trim Magic by manufacturer XIM. This bonding primer adheres very well and also does a nice job of blocking the tannin bleed. It goes on milky white and dries clear to milky white. The nosings don’t appear to be primed, but certainly are on all edges before installation.

We also tried to do the painter a favor and put a quick coat of white exterior paint inside of the bottom notch before installation makes this very difficult to do.

Today’s breeds of windows don’t really have a sloped window sill or a sill that notches out over the face of the siding underneath. So, even though the building envelope underneath was very well done, we still want to keep the water traveling out over the face of the siding. Because the bottom of the window unit is completely flat, we want to bond the new trim to the bottom edge of the window and stay bonded, so water doesn’t run in behind the nosing. This can’t be done by just a nice tight carpentry fit, so we have to leave a touch of a gap to bond the two with a tri-polymer caulking. Like I’ve said in the past, our favorite caulking is Lexel. By the way, did you know that tri-polymers are self-healing? This is because they stay so permanently flexible and gooey that if a bead of this caulking gets sliced somehow, the two ends will bond back together if they just touch. What’s next, are they going to start making cars that can parallel park themselves, or something?

Yes, we do prefer to do these repairs in wood or pvc. There are lots of pros and cons for each. Sometimes pvc is just a no-brainer; sometimes the pvc doesn’t make any sense. If we’re going to use wood, we just want to think about what species to use for the occasion. Cheery-O!

 

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