How to Install Metal Building Window Trim

What You'll Need
Aluminum Trim
Measuring Tape
Trim Nails
Cleaning Solutions

Window trim can be installed to the inside and outside of a window frame to weatherproof it and to make the property much more energy efficient. Metal building window trim can be applied to metal window frames as this offers a large degree of protection.

Installing your own window trim isn't actually that difficult as long as you have all of the necessary tools and equipment.

Step 1 - Bending Aluminum Strips

The first thing that you need to do is bend the aluminum strips so that they fit into your window. This will allow the aluminum strips to cover the entire window frame so that no wood is visible. Measure the window frame and mark the dimensions on your coil of aluminum trim. You will need to put two bends into the pieces of aluminum strips. Do this using a vice, hand brake or simply by pressing it over the edge of the table, try to make the folds as accurate and clean as possible.

Step 2 - Measuring the Window Frame

Next you need to measure the outside dimensions of the window frame, remember that the aluminum will be joined with a mitered cut at a 45-degree angle. This will mean that the lengths will be different between the inside and outside. If needed, cut the aluminum strips down. Always measure twice before cutting to ensure that everything is accurate.

Step 3 - Cutting the Metal Flashing

Now cut a strip of aluminum flashing which is the length of the window trim. Fix the metal flashing to the window frame so that the entire wooden frame is covered.

Step 4 - Trimming the Flashing

Once you've fixed the flashing up against the window frame you then need to use a pencil and straight edge to mark along the sides of the window frame. Use a pair of tin snips to cut the excess metal flashing away from the top of the window frame, take note of the angles.

Step 5 - Repeating with the Bottom

You will now need to check the metal flashing at the bottom of the window sill. Normally there is a cutout which you might need to cut out from the metal flashing so that the metal trim fits properly. Make this cut accurately so that you don't risk causing any damage.

Step 6 - Cleaning

Clean up the window sill and frame. If there are any cracks in the frame, they must be filled using putty and a putty knife. Sand down the filled areas of wood to make sure that they are level with the window frame. Cleaning the window frame can be done using a brush and some soapy water.

Step 7 - Caulking

If there are any gaps between the window trim and the building then these can be filled with caulking. It should also be possible to bend the metal slightly so that it fits correctly. Apply caulking and then use a dampened finger to smooth the bead of caulking so that it's level and flush with the trim and building.