The Great Exterior Fascia Debate

Exterior fascia is the workhorse of the roof system. It ties the rafters together and keeps the gutter system intact during rain events. It’s very common to install a utility grade sub fascia prior to installing the finished fascia. Also, very common is skipping the sub fascia altogether and installing an appearance grade, structural fascia such as a 2x6 member. To some degree, these regional variations depend on whether the design incorporates a closed soffit or exposed overhang.

Rain Country

In the Pacific Northwest for example, exposed overhangs are standard practice. Rafters are plumb cut at the tail end and run 12-24 inches beyond the top plate of the wall. Many builders choose a 5/4” exterior fascia product either 6 or 8 inches deep which is fastened directly to the rafter tails to complete the look. Most builders also install a 1×2 drip edge and flash the edge. According to Tracy Stromberg, Keystone Custom Construction, he uses 5/4 for the fascia and barge on 60% of his projects. When the project calls for a closed soffit, he uses a 2×6 plowed channel fascia to insert the soffit plank.  

Both the 5/4” and 2” materials are structural so I can hang the gutter and know it won’t come down,” he added. And with the amount of rain we get in Washington, that gutter is under load for much of the year. 

Hurricane Alley

In Florida, two preferences dominate. From Miami north to Daytona beach, everyone uses 2×6 and 2×8 primed and combed fascia, says Tony Merfeld, Market Development Mgr. for Belco. It’s a finished product, combed all sides so that it is reversible. Paint it and you’re done. However, on the west coast, builders use a utility 2×6 subfascia and wrap that with either a vinyl or metal soffit enclosure to completely enclose the wood.” Florida has seen widespread soffit failures from recent hurricanes. Nearly all of them are the result of poor detailing or improperly specified product. An industry taskforce is developing prescriptive codes for soffits and fascia to provide the Florida Building Commission with code language that will toughen one of the more common weak points in the building envelope.  

Texas Two-Step

Texas has two very different approaches to fascia. In central Texas, the majority of new construction features 2×6 or 2×8 plowed, primed and combed fascia. The finished fascia attaches directly to horizontal out lookers. However, in Houston and DFW, the use of sub fascia is more widespread. To complete these assemblies, a thin 5/16x6 fiber cement or 17/32”x6 OSB product or 5/8”x6” composite plank is attached to the face of the band.


exterior fascia

Rocky Mountains

Colorado and Utah have one of the greatest growth opportunities for Belco XT® preservative treated 2x fascia.

Colorado’s present practices are also predominantly a two-step system. A structural utility grade sub fascia is installed to the truss tails or outlookers by the framer. In a separate step, installed by the siding crew, a thin textured fascia of engineered wood material is installed over the sub fascia as the appearance cap. Two-step fascia details leave open the possibility of moisture entering between the two pieces, which may not be acknowledged until years down the road. And unlike other products such as Belco XT®, the backside of engineered wood is left unprimed.

Utah will use the same two-step process, but aluminum or vinyl fascia and soffit systems are very common on the tract homes. The metal and vinyl system is susceptible to expansion in warm weather, and contraction in cold weather. 

Desert High Heat

Phoenix, Arizona is a city that thrives in extremes.  Yes, the obvious is heat that can reach 125 degrees. Two feet of snow can fall in Flagstaff while Phoenix residents are wearing shorts and sandals.

For fascia applications the Phoenix market leans heavily toward primed wood fascia. The fastest growing primed wood product in Phoenix over that past five years is Belco XT® primed SPF fascia with a real preservative treatment under the primer as standard.  Belco’s XT 2×6 and 2×8 trim is a structural fascia that can be applied direct to the plated-truss tails and the outlookers. The quality and stability of Belco XT® Trim, along with a six-mil primer and the preservative treatment, has stood up to the extreme weather of the Arizona desert.  

Which exterior fascia method is better?

Like anything, both have their advantages and drawbacks. Let’s examine the major features. 

Material costs- The typical exterior fascia for osb, fiber cement, PVC and composites are less than 1” thick. On a lineal footage basis, these products appear to have a much lower price point than structural 2×6. Comparing the price per board foot for each product reveals a different story, however. Lumber, sold by the board foot, takes into account the three-dimensional volume and presents greater shadow lines. Retail pricing at a smattering of Big Box stores reveals the following averages for fascia (as of 03/22):  


Price ea. 


Board Feet 


Cementitious 1×6 12’ 





OSB 1×6 16’ 





Composite 1×6 8’ 





Wood (SPF) 2×6 12’ 





And don’t forget that the cementitious, OSB and composite boards will have the additional cost of the supporting sub fascia.  

Waste factors- Fiber cement is very brittle, especially at 5/16” thick. It’s common to see 20-30% in breakage. OSB is more flexible, but 16-foot pieces can break if mishandled. Edge swell might occur if the product is left out in the rain. Overall, OSB has a low waste factor. Solid wood is prone to knots, wane and warping. However, today’s specialty wood manufacturers have realized that to compete against the perfect man-made products they need to be as close to perfect as nature allows. For this reason, today’s primed wood fascia also has a very low waste factor. 

Labor- Primed wood fascia is a single-step installation. Most man-made products require a sub fascia making it a two-stage build.  Solid wood also outperforms its man-made counterparts in workability.  

Consistency- Fiber cement is straight, and every plank looks identical. Like fiber cement, osb is also very uniform. Every piece is manufactured with the pattern stamped on the face. 

Aesthetics- Both fiber cement and osb tout their wood-like appearance. Solid wood is the standard that everyone tries to match. Nothing can replace the warmth and beauty of real, natural wood fascia.  

Belxo XT Trim exterior 2×6 and 2×8 fascia boards eliminate the need for sub fascia and offer an affordable, reliable, and beautiful trim option. 

Download the Window Trim Cutlist Guide

Reduce trim waste with this guide to the optimal window trim cutlist. Download the Guide

Our Happy Customers

Preservative treated, primed, and available with a combed, brushed, resawn, or smooth face. The real beauty of your home comes to life through a well made trim package.

Preservative treated, primed, and available with a combed or smooth face. These glulam columns are strong, beautiful, and enhance any exterior design. 

Belco XT®-T&G is graded smooth face with edge vees on all four edges and a textured ungraded back.

Love Talking Trim?

Download our product one-pager to learn more about Belco XT products