Replacing a windowsill can be easier than it seems, you might only need to count with the necessary tools and follow several steps. We will provide you with some useful tips through the next few lines, although you might also find useful to consult an expert for more specific guidance.

If your new windowsill will be painted, you might want to use pine instead of more expensive wood such as mahogany or oak. In a painted windowsill it is not important to use a nice looking wood, and you might save some money by choosing an inexpensive kind. On the other hand, if the windowsill will not be painted, you should choose a good wood, since it will be an important part of the appearance and style of that room.

To start, you should remove the old sill, and this implies a few simple steps. First of all, you should measure the windowsill as it is, writing down what its length, width and thickness is, since you will need this as guidance for the new one. Next, remove the side pieces and the sash channel trim. Once you have done this, you should remove nails in the trim with pliers, until you are able to access and remove the old sill.

Once you have removed the old sill, you should buy new lumber and finish nails. On the lumber you bought, trace the same pattern of the old one. After this, you will need a saber saw in order to be able to cut it, preferably using a fine toothed blade. Once it is cut, you should sand it and make sure it is as smooth as possible.

After the new sill is ready to be installed, you should fit it in place, holding it with nails. After that, replace the trim and nail all the remaining pieces making sure everything is right on place and firm. If, after installing the new windowsill you find that there are any old nail holes, you should fill them with wood putty. After that, and if it is planned, you can paint the new windowsill and it will be ready.