Installing Valley Flashing

What You'll Need
Tape measure
Metal roof nails
Caulking gun

Installing valley flashing in your roof can be a daunting task and requires careful preparation. A valley is the part of your roof where two descending parts of the roof meet each other. A flashing on the other hand is a waterproofing material used to prevent leaks on roofs. It is necessary to install flashing in your roof valley as valleys are prone to developing leakages. Valley flashing is made of aluminium, metal, PVC, galvanized steel or lead.

Installing a valley flashing to protect your roof from water damage can be done with the following materials and steps.

Step 1 - Determine the Number of Flashing that You will Need

Determine the number of flashing that you will need by measuring the span of your roof valley using a measuring tape. For each piece of flashing that you will need, add an extra four inches for the overlapping pieces of flashing. You can purchase valley flashings at any local hardware shops and home improvement centers.

Step 2 - Install the Valley Battens

Install the valley battens on the sides of the roof that you want to place the valley flashing. A batten is a roofing component made of a thin layer of metal, plastic or wood and is used as a fixing point for roof tiles and roofing sheets. Place the flashing on the upper portion or the upper flange of the batten. Lay the flashing in a way that an inch of the flashing protrudes over the edge of the upper flange of the batten.   

Step 3 - Install the Flashing

Apply a thin layer of caulking on the edge of the upper flange of the batten using a caulking gun. Lay and press down the flashing over the caulking to secure the flashing into the flange. The caulking is not enough the firmly secure the flashing on top of the flange. To do this you must hammer metal roof nails into the flashing through the flange.

Step 4 - Install the Rest of the Flashing

Install the rest of the flashing until you have covered the entire roof valley. Make sure to allow each piece of flashing to overlap at least four inches with the previous piece of flashing. Overlapping each piece of flashing to each other minimizes gaps in the flashing where water can enter.

Step 5 - Fill in the Gaps

Fill the gaps between each piece of the flashing with caulking using a caulking. Pay particular attention to the gaps where the flashing pieces overlap each other. You can also apply granules of wood pellets to the cut areas of the flashing to protect it from rust.

Installing valley flashing will not only prevent water from leaking into your home framing and siding but also improve the aesthetics of your roof as well as maintaining the integrity of your roof structure. Installing valley flashing is a time consuming task and should be done with care since you will be working on top of the roof.