Furring strips are commonly used in metal roof installations to create a level surface and to provide ventilation.
However, whether or not you need to use furring strips for a metal roof depends on several factors, including the type of metal roof you are installing and the slope of your roof.
If you are installing a standing seam metal roof, which typically has a raised seam that joins adjacent panels, you may not need to use furring strips if the slope of your roof is at least 3:12 (14 degrees).
However, if the slope is less than this, you may need to use furring strips to prevent water from pooling and to ensure proper drainage.
On the other hand, if you are installing a metal shingle or a metal tile roof, which typically have a flat profile and interlock with adjacent panels, you will likely need to use furring strips to create a level surface and to provide ventilation.
In summary, whether or not you need to use furring strips for a metal roof will depend on the type of metal roof you are installing and the slope of your roof.
When is it mandatory to use furring strips for metal roofs?
It is generally recommended to use furring strips for metal roofs in most cases, but there are certain situations where they are mandatory. Here are some examples:
When installing a metal roof over an existing shingle roof: If you are installing a metal roof over an existing shingle roof, furring strips are usually required to create a level surface for the metal panels and to prevent moisture buildup between the shingles and the metal panels.
When the roof deck is uneven or damaged: If the roof deck is uneven or damaged, furring strips may be necessary to provide a level surface for the metal panels and to help prevent damage to the panels.
When installing certain types of metal roofing: Some types of metal roofing, such as standing seam metal roofing, require the use of furring strips to provide a secure attachment point for the panels.
When required by local building codes: Some local building codes may require the use of furring strips for metal roofing installations to ensure that the roof is installed safely and securely.
What size screws will you need to install metal roofs on furring strips?
Here are some general guidelines for screw size:
For wood furring strips, you may use wood screws that are at least long enough to penetrate the wood by a minimum of one inch. So, if your furring strip is 1 inch thick, you might consider screws that are at least 2 inches long to ensure a secure grip, On Amazon you can find these #8 x 2″ steel screws.
You can also find the #8 x 2″ steel screws in red.
For metal furring strips, self-tapping metal screws are usually used, and the length will similarly depend on the thickness of the furring material. Again, you’ll want screws long enough to fully engage the furring strips but not so long that they penetrate through the other side.
The screws should be long enough to go through the metal roofing material and securely into the furring strip below. A 1-inch or 1.5-inch screw is often used for this, but the length can vary based on the thickness of your roofing material and furring strips.
On Amazon you can find these 1-1/2″ Length self-drilling screws, they are ideal because they have a neoprene washer to help seal the screw hole and prevent leaks.
Screw Gauge: As for the thickness or “gauge” of the screw, #12 or #14 screws are commonly used for this kind of work, but consult the furring strip manufacturer’s guidelines to be sure.
Screw Head: Use screws with heads that are appropriate for the type of driver you are using. For roofing, flathead screws are often used because they can sit flush with the material.
Material: The screws should be corrosion-resistant, especially for exterior and roofing applications where moisture is a concern. Stainless steel or coated screws are commonly used options.
What is the purpose of furring strips on metal roofs?
Furring strips are often used on metal roofs to provide a level surface for the installation of the metal panels and to create a gap between the metal panels and the roof deck or sheathing.
The primary purpose of the gap created by the furring strips is to provide ventilation and allow air to circulate between the metal panels and the roof deck.
This ventilation helps prevent moisture buildup, which can lead to issues such as rust, corrosion, and mold growth. It can also help regulate the temperature inside the building, reducing the load on heating and cooling systems.
Furring strips can also help address issues with an uneven roof surface, by providing a level substrate for the metal panels to attach to.
This can help prevent damage to the panels due to uneven weight distribution and can improve the overall appearance of the roof.
Overall, the use of furring strips on metal roofs can help improve the durability, functionality, and lifespan of the roof.
Can you put metal roofing directly on the rafters?
It is generally not recommended to install metal roofing directly onto rafters.
Rafters are typically spaced too far apart to provide a solid base for the metal roofing panels, which can lead to sagging or buckling over time. Additionally, rafters are not designed to provide the same level of support as a solid roof deck.
Instead, a solid roof deck made of oriented strand board (OSB) or other approved materials should be installed over the rafters, with the metal roofing installed on top of that. The roof deck should be at least 15/32″ thick for 16″ on center support spacing, or 23/32″ thick for 24″ on center spacing.
Can you install metal roofing directly to plywood?
It is not recommended to install metal roofing directly onto plywood. Plywood is a type of wood-based sheathing that can absorb moisture and expand and contract with changes in temperature and humidity.
This movement can cause the metal roofing panels to buckle, warp or develop other types of damage over time.
Instead, a solid roof deck made of oriented strand board (OSB) or other approved materials should be installed over the plywood, with the metal roofing installed on top of that.
The roof deck should be at least 15/32″ thick for 16″ on center support spacing, or 23/32″ thick for 24″ on center spacing.
In some cases, furring strips may also be installed over the roof deck to provide a level surface and a gap for ventilation between the metal panels and the roof deck. This can help prevent moisture buildup and improve the longevity of the roof.
Additionally, it is important to make sure that the sheathing is properly secured to the roof framing and that any gaps or holes in the sheathing are filled and sealed to prevent moisture infiltration.
This will help to ensure that the metal roofing is installed properly and will last for many years.
Spacing of furring strips for metal roof
The spacing of furring strips for a metal roof will depend on a variety of factors, including the type of metal roof being installed, the size and shape of the panels, the slope of the roof, and the local building codes and regulations.
As a general guideline, furring strips for a metal roof are typically spaced between 12 and 24 inches apart, although some manufacturers may specify a narrower or wider spacing depending on their product requirements.
Here are some general guidelines for furring strip spacing:
- For low-slope roofs (2:12 or less), furring strips should be spaced no more than 16 inches apart.
- For steeper roofs (greater than 2:12), furring strips can be spaced up to 24 inches apart.
- For standing seam metal roofs, furring strips should be spaced no more than 18 inches apart.
- For corrugated metal roofing, furring strips can be spaced up to 24 inches apart.
The closer the spacing of the furring strips, the more support they provide to the metal panels, which can help reduce the risk of sagging or buckling.
It is important to note that the spacing of the furring strips must also be appropriate for the underlying roof deck and the local building codes.
The spacing should be close enough to provide adequate support for the metal panels, but not so close as to create an excessive amount of penetrations in the roof deck, which can weaken the structure and compromise its integrity.
Can you install a metal roof over singles?
Yes, in most cases, it is possible to install a metal roof over shingles. This process is commonly referred to as a “metal-over-shingle” or “re-roofing” installation.
The advantage of a metal-over-shingle installation is that it can be faster and less expensive than tearing off the existing shingles and installing a new roof deck.
Additionally, leaving the shingles in place can provide an additional layer of insulation and weather protection.
However, there are some important considerations to keep in mind when installing a metal roof over shingles. The roof deck and shingles must be in good condition, with no signs of rot, damage, or deterioration.
Additionally, the existing roof must be flat and level, with no high spots or low spots that could cause the metal panels to buckle or warp over time.
The metal roofing panels should be installed over a layer of underlayment, which provides an additional layer of protection against moisture and helps to reduce noise from rain and other sources.
It is important to ensure that the underlayment is compatible with both the metal roofing panels and the shingles and that it is installed in accordance with the manufacturer’s guidelines and local building codes.
Finally, it is important to note that some local building codes and regulations may prohibit or restrict the installation of metal roofing over shingles.
Can you put a metal roof over shingles without furring strips?
It is possible to install a metal roof over shingles without furring strips, but it is not recommended. Furring strips provide a flat, level surface for the metal roofing panels to be installed on, and they also help to reduce noise and provide ventilation for the roof.
If you install metal roofing directly over shingles, the shingles may show through the metal panels and cause an uneven appearance.
In addition, the metal panels may conform to any irregularities in the shingle surface, which can lead to a wavy or uneven appearance.
Installing metal roofing without furring strips can also increase the risk of moisture buildup and ventilation problems. Furring strips provide a gap between the metal panels and the shingles, allowing air to circulate and moisture to escape.
Without this gap, moisture can become trapped between the metal roofing and the shingles, leading to rot, mold, and other problems.
In general, it is best to install furring strips over the existing shingles before installing the metal roofing. This will provide a solid, level surface for the metal panels, and help to ensure proper ventilation and moisture management.
If the existing shingles are damaged or deteriorated, they should be removed before installing the furring strips and metal roofing.
Where do you put screws on a metal roof?
The placement of screws on a metal roof depends on the type of metal roofing system being installed. However, in general, screws should be placed in the high points of the metal panels, typically along the ridges and at the ends of the panels.
This helps to ensure that the screws are not visible from ground level and helps to prevent water from pooling and potentially leaking through the screw holes.
The exact placement of screws will depend on the manufacturer’s recommendations, as well as the size and shape of the metal panels.
Some manufacturers may recommend placing screws every 12 inches, while others may recommend placing them every 16 inches or more.
It is important to follow the manufacturer’s recommendations and local building codes to ensure that the metal roofing is installed correctly and will provide a long-lasting, durable roof.
In addition to placing screws in the high points of the metal panels, it is also important to use the correct type and size of screws for the specific metal roofing system being installed.
The screws should be long enough to penetrate through the metal panels and into the underlying roof deck or purlins and should be made of corrosion-resistant material to help prevent rust and degradation over time.