If your house is old enough to have rotting window sills you will need to know how to replace them. Here in this article we will talk about replacing this unsightly part of your window. The tools you will need are; caulking gun, hammer, screwdriver, saw, lumber, pencil, measuring tape, and screws or nails.



1) Raise the window and start removing the rotted wood of the sill. If some of the sill is still solid, use a power saw or large screwdriver to remove the interior parts. Try to keep the exterior edges in one piece.



2) Once the sill is out and the outer edges are still together, use this to make a template for your new sill. Use a ruler or other measuring tool to measure a replacement top plate. If your sill is in two or more pieces, keep them anyway. You may be able to make a template nevertheless.



3) Put the rotten sill on a piece of two by six lumber to trace around. This will be the outline to cut out for your new window sill. Use a piece of one by six lumber to trace out a template for your new top plate.



4) Use a saw to cut out the sill and the top plate. A table saw is best, but most any saw will do.



5) Put your new sill in the window and put the top plate on top of it. Use stainless steel or galvanized screws to secure the pieces to the window frame. You can install screws on the exterior for the bottom sill.



6) Use caulking to seal any cracks that may exist in your new sill. If you have trim to reinstall, go ahead and install it. Your window is now ready for more years of use.



Do not forget to use safety glasses while you cut your wood pieces.