Modern roofs often have several layers. If your plywood roof is sagging or rotting, you must fix it immediately before installing a metal roof.
Personal experience shows that addressing these underlying issues early prevents costly repairs later, as the metal panels depend on a solid base for proper installation and longevity.
Key Considerations for Metal Roofing Installation Over Plywood
| Consideration | Description |
|---|---|
| Plywood Condition | Must be in good shape; repair any sagging or rot before proceeding. |
| Underlayment | Provides additional moisture protection; consider using a high-quality type. |
| Slip Sheet | Optional but recommended for extra moisture defense. |
| Panel Overlaps | Ensure proper overlap to avoid leaks and secure with galvanized screws. |
How to Install Metal Roofing Over Plywood in 8 Steps
You may wonder why you should use metal roof replacement. Metal is considered a wise roofing material choice nowadays, considering its visual and functional aspects. Among various types of roofing, metal stands out for its durability and aesthetic appeal.
The metal roof needs a solid deck structure. Plywood serves as a solid base to support the weight of metal panels. Before installing the metal panels, ensure that the plywood is clean and free from raised nail heads. Applying building paper or underlayment for added protection is essential, as it can enhance the roof’s exposure durability classification.
Read also: How to Build a Metal Roof Over a Deck
Follow these steps when installing metal roofing over plywood after ensuring it is clean and all the nails are hammered down.
- Set the waterproof plywood on the roof’s flat surface, ensuring rows overlap and secure with roofing nails. A slip sheet between the metal roofing and plywood can provide additional protection against moisture. It’s vital to inspect the plywood before installation.
- Calculate your roof edge’s length. Then, cut the metal flashing and install it on the edge of the roof by using a nail and hammer. Install the gutters according to the fitted size, then secure them by using a hammer and nails.
- Draw a vertical line about 0.25 inches away from the rake edge. Start from the left side of the roof, setting the metal panel at the bottom corner to the roof’s ridge, ensuring a 1-inch overlap between edges. Secure the roof panel with galvanized screws spaced 12 to 16 inches apart.
- The next step is to line up the second panel over the first panel straight. Their edges must overlap by about 12 inches. Secure the metal roofing panel at a distance of 16 inches or 12 inches between each other of the deck using a galvanized metal screw.
- Continue step 4 until you arrive at the roof’s peak. Calculate the length required to reach the last upper panel and mark it by using a pencil. Then cut the metal panel accordingly using metal snips.
- Come back to the bottom corner of the roof. Start installing another metal roofing panel row. Set the rib on the left part of the metal panel to the right part of the rib on the next installed metal panel.
- Again, continue step 7 for every row until you have installed all panels.
- Finally, place the ridged metal on the highest point of your roof and install pipe boot kits throughout the vent pipes.
Personal Experience Insight: When securing the panels, it’s essential to check for buckling or misalignment immediately, as these can lead to significant issues later.
Read also: Metal Roof Flashing Types
I prefer not to use underlayment, which will only save you some money in the short term—several hundred to one thousand dollars, depending on your house’s size.
Note on Underlayment:
Opting not to use underlayment might save some budget in the short term, ranging from several hundred to one thousand dollars, depending on your house’s size. However, it’s important to remember:
“Skipping underlayment may lead to moisture issues later, causing damage to both the metal panels and the plywood base, which could require expensive repairs.” Experts strongly advise using underlayment, especially in regions prone to heavy rainfall or humidity.
When hiring roofing contractors, ensure they are experienced in metal roof installations to guarantee the best results.
