What Is the Spacing of Furring Strips for Metal Roofs?

Every type of roof has unique features that help it stay put and protect your home. If you’re installing a metal roof, one of the most common features to include are furring strips. These carefully placed pieces of wood stripping, which elevate your roofing material off of your roof decking, have a big impact—but only if you install them correctly. This guide will explain the perfect spacing of furring strips for metal roofs.

What are Furring Strips?

Furring strips for metal roofs are pieces of lumber that sit between your roof deck and metal roofing to maintain a void underneath the metal panels. This type of wood stripping comes with a number of benefits, which include:

• Increased insulation

• Improved ventilation

• Improved drainage 

• Minimized condensation

• Reduced interior noise during rainfall

• Leveling a damaged or uneven roof deck

Remember: metal roofs can get hot in the sun, and they can transfer heat readily through roof decking, which heats up your home. Furring strips help minimize heat transfer between your metal roof and roof deck, which can increase your home’s energy efficiency in hotter climates. Since they also help reduce moisture buildup, they’re typically recommended or even required by local building codes.

What Spacing Is Recommended for Furring Strips?

As a general rule, furring strips are usually spaced somewhere between 12 inches to 24 inches apart. Building codes vary, and certain manufacturers may have slightly different instructions. The type of roof you have and the roof slope will also affect the ideal spacing. The closer together you place your strips, the more support they’ll give your roof, but the higher your material costs will be.

Factors for Determining the Spacing of Furring Strips on a Metal Roof

Most roofs will use furring strips spaced 24 inches apart on center, but there are a few factors to consider to make sure you get the proper spacing.

Type of Roof

Certain types of metal roofing need more furring strips than others. Thicker, stronger metal roofs, like low gauge standing seam roofs made out of strong steel, will stand up better to heavy loads from foot traffic or snow accumulation, so you can space furring strips 24 inches apart. A higher gauge metal roof (thinner), aluminum standing seam roof, or corrugated roof needs more support from underneath, so you’ll place your furring stips closer together. Here are some spacing guidelines based on whether you use a standing seam metal roof or a screw down metal roof, or you opt for another metal roof design.

• Corrugated metal roofing: space your strips up to 16 inches apart.

• Standing seam metal roofing: space your strips up to 24 inches apart.

• Metal shingle roofing: space your strips up to 12 inches apart, but ensure all shingles are supported.

Slope of Roof

The steeper the slope on your roof, the further apart you can space your furring strips because steeper roofs shed snow accumulation more easily and are less likely to have to support heavy loads. You’ll need to know your roof pitch before you begin installation. Here are some guidelines:

• Low slope (a pitch of 2/12 or less): space your strips up to 12 inches apart for a lower pitch metal roof

• Moderate slope (a pitch of between 2/12 and 4/12): space your strips up to 16 inches apart

• Steep slope (a pitch greater than 4/12): space your strips up to 24 inches apart

Building Codes

Local building codes likely have rules and regulations when it comes to the spacing of furring strips for a metal roof. Building departments base these on climate, so homes in areas that see excessive snowfall may have regulations that require furring strips spaced 12 inches apart as opposed to the standard 24 inches. Always check with your local building code before deciding on the proper spacing.

How to Place Furring Strips Properly

Spacing your furring strips properly should always begin with a review of local building codes, as you’ll want to ensure your roof remains in compliance. Provided you meet those regulations, you can choose what spacing works best for your home. Go with a shorter distance of 12 inches if you have a low-slope roof and see a large amount of snowfall each year. Go with a wider span of up to 24 inches if you have a durable steel metal roof that’s unlikely to bend under the weight of foot traffic and snow accumulation.

Common Mistakes to Avoid When Spacing Furring Strips

There are a few key common mistakes you should avoid when spacing furring strips for your metal roof.

• Not placing furring along the sides and top of the roof slope: A common mistakes some DIYers make is starting at one end of the slope and installing furring at the proper spacing but then not placing an extra furring strip along the other side. This will leave a portion of your roof unsupported and increases the risk of leaks.

• Not using foam closure strips: Along the bottom of each slope, install foam closure strips instead of furring to allow for better drainage and ventilation.

• Not marking where your furring strips are: Once you place your panels and start screwing them down, it’s easy to lose where the furring strips are below. Use a chalk line to mark the center of the strips for attaching screws.

• Not lining up the strips properly: The underside of your metal roofing will have peaks and valleys, and you want to make sure the furring strips naturally fall on any curve back toward the roof deck for proper support.

Should I Replace My Existing Furring Strips?

Furring strips are made from wood, so if they start to rot, you will need to replace them. This type of installation is best done by a metal roofing company near you. The roofer you hire can also decide if it’s safe to reuse the existing furring strips or if a full replacement is necessary.

When you set your budget, keep in mind that furring strips add to the cost of a metal roof. It’s typically a worthwhile expense because it will help prevent issues that prematurely age your roof.