How to Replace a Flat Roof Vent

What You'll Need
Intake vent
Exhaust vent
Roofing cement
Roofing felt
Finishing nails
Electric drill

Flat roofs are becoming increasingly popular due to modern architecture, but a flat roof vent can be difficult to maintain. Flat roofs are harder to ventilate because they lack the natural air inlet called soffits that a pitched roof provides. Soffits are holes underneath the roof caused by eaves which allow the air to flow. This can cause a flat roof to become more susceptible to damage caused by weather conditions such as rain and snow. Without the proper air flow, a flat roof can eventually cause structure decay by trapping heat and moisture in the attic area. Properly built flat roofs will have a vapor barrier. Vapor barriers prevent moisture from building up and allows moisture to escape. It is important to select a flat roof vent that will supply adequate ventilation based on the size of the structure. There are various styles of roof vents that can be used, but a flat roof must always have an intake vent and an exhaust vent. Always check local building codes to ensure that the proper materials and techniques are being used.

Step 1 - Removing Old Vents

Remove the old vents you wish to replace according to the manufacturers instructions. Clean and remove all shingles, flashing and roofing felt before installing the new vents. Inspect the roof for any damages around the vent area and repair accordingly. Measure the size and shape of the new vents and adjust the size of the existing holes as needed. 

Step 2 - Installing New Vents

Install the new vents according to the manufacturer's instructions. Prime the top and the bottom of the vent flange and allow to dry completely. Next, coat the bottom of the vent flange with roofing cement and mount into place using screw and an electric drill. Use silicone as needed to prevent leaks around the screws. Coat the top of the flange with roofing cement. Cut roofing felt to size and position over cement creating sealing any gaps between the flange and the opening. Apply pressure using your hands to bond the roofing felt to the flange. Apply a second layer of roofing felt using cement to bond the layers together.

Step 3 - Finishing Roof

Cut flashing to proper size using heavy duty scissors. Remove paper backing from flashing tape and cover flange and surrounding roof area. Overlap the flashing to create a stronger seal. Press into placing being careful not to stretch or manipulate the flashing. Bond all seams using roofing cement. Allow the roofing cement to set before applying the shingles. Attach the shingles to the roof using finishing nails and a hammer. Test the roof for leaks and repair if necessary.