If not, water might eventually find its way inside, and after a while, this leads to rotting, which can be a challenge to repair. All you need to do is get some new sills from a reputable vendor like the Skirting Board Shop, some tools, and some safety gear.
Once you’re done, go ahead and remove the casing gently, ideally using a utility knife to ensure wood chips don’t get stuck on the sliding. You should also ensure the trim remains in excellent condition by partially taking out every nail and pulling it out.
You should then create holes after every 16 inches or so across the back edges and the new window sill’s front side. But before you even spread this epoxy agent using a paintbrush on all the destroyed areas, start by mixing it with a hardener as stated in the manufacturer’s manual.
After mixing these two components, spread them with a knife across the sheet of clear, firm plastic. Using 3½–inch deck screws, attach the new window sill onto the adhesive while passing through the plastic and through the wood.
Once the head is around ¼–inch under the window sill’s surface, stop and wipe away and excessive adhesive oozing out. To ensure the window’s aesthetic appeal isn’t ruined by the presence of screw heads, you need to cover them up.
Using acrylic latex caulk, fill the new sill’s edges and go ahead and change the trim, seal the nail holes. Extreme weather is the enemy of wood sills and, in most cases, leads to its interior starting to rot.
If you didn’t know what needs to be done to repair the rotten wooden sills, this guide has provided you with the steps you need to follow. Many of these homes are historical and their owners work hard to keep them in good condition.
Fix any small or medium cracks in your concrete window sill with caulk. Fit the narrow tip of a bottle of silicone latex caulk into each crack and overfill it by about ¼ inch.
Fill pitted areas or recreate corners and edges with prepared concrete patch. Use a paintbrush to apply concrete bonding agent to the entire window sill.
Apply a 3/8-inch-thick layer of concrete all over the sill with a trowel, following any contours to mimic its original shape. Insert the injection ports included in your kit along the crack, pushing them in as far as possible.
Use a paintbrush to coat the damaged area inside and out with the epoxy adhesive. Stop filling the current port when the epoxy is visible in the hole of the one above it.
Use a putty knife or paint scraper to remove any excess epoxy on the window sill. Use a utility knife, and a hammer if necessary, to carefully break and remove any caulking or sealant that's binding the old sill to the window frame.
If your sill is sloped, you'll also need to remove the wooden supports that are holding it up. Use a rag and utility knife to clean away any debris left on the window frame.
If parts of the sill or caulk remain, use sandpaper and solvents to clean the area. Good to Know For major rot problems, contact an expert for advice.
Place your old sill over the selected board and draw its outline with a carpenters pencil. A jigsaw is useful for secondary cuts and shaping the sill if you have a more decorative design in mind.
Make the required angle cuts, so the sill fits tight against any existing weatherproofing material. Make any necessary adjustments and add shims if needed to ensure that it's level before final placement.
Toucan apply caulk to the screw heads when you've finished to help hide them from view. Good to Know If you use pressure-treated boards for the new sill, use fasteners labeled for treated lumber.
If you removed any interior window trim, wait until the caulk is fully cured (about 24 hours) before replacing it. With four seasons, humidity, rain and snow the exterior wood around our home has a lot to withstand.
One of the most common places you will find exterior wood rot is your window sill. Because our homes are exposed to four seasons, temperature changes and humidity, wood rot is common on windowsills, especially those that have been neglected.
To avoid replacing your window sill, toucan work on regularly maintaining to help prolong its lifespan. Apply a waterproof sealer every year or two, and regularly check for cracks and chips.
If you find your window sill is starting to crack or chip, fill them in and repair them before the wood begins to rot. But, if you’ve waited too long and have found rotten wood, it’s time to repair or replace your window sill.
You might need to use a pry bar to get this process started, and then move on to a claw hammer. Depending on how rotted your window sill is, it may be an easy or more difficult job.
Be sure you have waterproof construction adhesive and 3 1/2 inch deck screws on hand. You will apply the adhesive to the back of the new window sill and then drill it into place.
Replacing your exterior rotted wood window sill is a labor-intensive job. Since you are already investing the time to get the job done, you may want to consider repainting the rest of our windowsills and trims to keep things consistent.
We recommend you always select a repair company with proper insurance and experienced employees. This will save hassle if something goes wrong, and it is more likely you will get the job done right the first time when you hire someone with experience.
Replacing exterior rotted wood windowsills is an imported part of home maintenance. But when water gets trapped in or against them, as happens with improperly flashed windows, rot can take hold.
It costs less than a piece of clear, milled red cedar and is printable, but no matter how many times it gets wet, it can 't rot. Step 1 Photo by Ryan Benji The casing comes off to clear the way for removing the old sill.
Slice through the caulk bead between the siding and the casing, then carefully pry off each piece. Make sure the flashing behind the casing is intact and properly installed behind the siding.
Step 2 Photo by Ryan Benji Make a plumb cut flush with the sheathing along the length of the rotten sill. Step 3 Photo by Ryan Benji Repair any rotten spots on the old sill with epoxy.
Drill pilot holes every 16 inches or so through the new sill's front and back edges. Step 4 Photo by Ryan Benji Press the new sill into the adhesive, and immediately clamp it in place by driving 3½-inch deck screws through the plastic and into the wood.
Step 5 Photo by Ryan Benji Cover each screw head with a dollop of a white, two-part acrylic adhesive, such as Landfill Pasture. Step 6 Photo by Ryan Benji Squeeze a bead of caulk beside the ends of the siding, and nail the new casing in place.
Set the nail heads slightly below the surface, and cover each one with a dab of the two-part adhesive. If sills are sandstone, the stone tends to deteriorate with age, exposure to rain, snow and freeze-and-thaw cycles.
While some do-it-yourself sites recommend epoxy-based fillers, with the right mortar, tools and approach, homeowners can repair and maintain the natural appearance of sandstone windowsills. Make 3/4-inch cuts around any unsound area on the sandstone sill with a wet diamond blade.
Cutting a boundary around the compromised sandstone makes chisel removal more precise. Chip away the stone defined by the diamond cuts with a pneumatic hammer and chisel.
If you're repairing a large section of the windowsill, space the mechanical keys approximately 3 inches apart. Where sills are particularly deep, create two staggered rows of mechanical keys.
Spread a thin coat of the slurry layer with the trowel to the sandstone sill and work it into the surface. Pigments and stones are added as needed to match the original color and texture of the sill.