How to cut your siding pieces around doors or windows

This week, our Jill of All Trades, Jill Washburn, helps us finish up the siding by showing us how to do some of the more challenging pieces like cutting around doors and windows and such. The hardest part, says Jill, is making sure that your measurements are spot on so that you’re not wasting pieces of siding due to misplaced cuts.  

Jill says that using a scrap piece of siding and holding it up next to the window or any other element that you need to work around can help you get an accurate measurement. Just clip the scrap into place, as you would if you were installing it, and mark where you need to make your cut. Make sure, says Jill, that you factor in the amount that the siding needs to fit into the J-channel.

Once you have your measurements figured out, you’re ready to mark it onto a piece of siding and make your cuts. Jill just uses a pencil to mark the siding. That way, if she decides to make changes, the old marks will come off.

With the marks in place, it’s time to make the cuts. For the vertical cuts, Jill generally just uses tin snips. A sharp pair of tin snips will cut through vinyl siding surprisingly easy. Horizontal cuts will generally be a little tougher because the are often longer and more difficult to get the tin snips in. For those, Jill lays the siding piece on a firm work surface and uses a metal straight edge and a razor knife. Just repeatedly scoring a line along the straight edge will cut through the siding, allowing you to bend it and break it away.  

PRO TIP: Wear protective gloves, preferably good leather ones. One slip of the razor knife can cause a lot of damage, and it’s easy to have happen on siding because the surface is so smooth.

Once you finish your cuts, you’re ready to hang that piece. Just like last week, you’ll want to clip the bottom edge of the siding to the top of the previous row, making sure that it's full engaged. It may be a little tricky fitting the pieces into the J-channel, but Jill says that the siding and the J-channel are both flexible, so you should be able to coax them together. Jill advises that this will be easier on a warmer day, because the siding retains a little more of its flexibility in warmer temps.

Once it’s fitted into place, it's ready to nail. Just like before, the siding should be nailed in the center of the nailing slots, with the nails left just slightly loose, to allow for expansion and contraction due to temperature change. And, like before, nails should not be more than 16” apart. Depending on how far the piece spans under things like windows, you may want to use a siding adhesive in the J-channel under the window to help the siding stay in place over time. It comes in caulk form and is easy to use.

Once you work your way to the top, you’ll need to finish off the wall. For gable ends, or places where there is not a straight horizontal line at the top, you may want to have J-channel. This is what Jill usually chooses, to keep the look consistent. When you reach the very top, you may have to drive a tiny nail through the top edge of the siding, just to keep it in place. Jill recommends aluminum nails for this, as they will not rust or discolor the siding over time.

To finish a wall where the top line is horizontal and straight, there is a crimping tool that you can use that will press little flaps into the top edge of the siding. Those little flaps will then engage with a piece of utility trim that you can use at the top of the wall. That utility trim will lock the top edge of the siding in, no matter where you’ve had to cut it.

PROJECT RATING:  Challenging, but not difficult

To watch Jill guide you through the process, just click on the video player above.