Metal roofing tends to get lumped together into one big group of roofing when in reality there are many different types of metal and categories of metal roofing. Different types of metal roofing have been designed to serve different applications and the best outcome always results from using the right type of metal roofing and profile in the applications it was designed for. There is not a one size fits all metal roof.
Over the last ten to fifteen years a screw down metal or pole down metal as it commonly called has become widely popular and is being used in about every application possible, right and wrong. The result? Leaks on metal roofs that weren't supposed to ever leak and metal roofs not lasting even half the time that the roofing contractor said they would. A major reason for this is that the pole barn metal or screw down metal is being used in places where standing seam should have been used.
We highly recommend that pole barn metal be used on barns or warehouses whose structures were designed for this type of metal and that standing seam metal roofing be used on homes and businesses with finished interiors and whose roof has solid wood decking or open steel framing typically found on pre engineered metal buildings. In the next few paragraphs we will make three different comparisons between standing seam and screw down type metal roofing.
Standing Seam Metal Roofing vs. Screw Down Metal Roofing
1. Exposed Screws vs. No Exposed Screws
Probably the easiest and most easy way to understand comparison between standing seam and barn metal is the screws. Pole barn metal gets attached to a structure by installing screws directly through the face of the metal into the wood substrate. The result is exposed screws in lines across the entire roof two feet on center. It requires roughly 70 screws per sq of roofing ( 1 sq = a 10' x 10' area) to attach screw down metal. That quickly adds to between 2,000 and 3,000 screws on an average sized home of 1,800 sq. ft. in size. The screws rely on a rubber washer to seal water out of the roof. In order for the rubber washer to work correctly, the screws must be installed at a 90 degree angle with the roof pitch and must not be over tightened nor under tightened. But even when all 2,000 plus screws are installed correctly the rubber washer rarely last more than 12-14 years at best with many roof screws failing as early as year 7. One other huge issue with the screws is that the type of structure designed to use pole barn metal have 2 x4 purling that the screw goes into. The 2 x 4 provides enough "meat" for the screw to bite into solidly, but most home and wood framed businesses have 1/2 plywood or OSB boards for roof so the screws don't get the bite they need to stay put.
Standing seam eliminates exposed screws by using a clip system to attach to a structure. The next piece of metal then covers over the clip which leaves the screws underneath the metal roof. The fact that standing seam metal roofing doesn't have exposed screws is a major reason it last so much longer than screw down metal. The clip also allows the metal to expand and contract with pushing on or against itself, trims, flashing, or screws.
2. Standing Seam's Interlocking Pieces and Part vs. Just Parts of Screw Down Metal
Standing seam metal roofs have the ability to be interlocked or hooked onto one another. This is done by creating what is called a "hem" on the roofing panel and then hooking the hem onto another piece of metal roofing assembly. A hem is a 1" bend that allows for the hook up but also means that the standing seam metal roofing can move or expand and contract without breaking water tights seals around trims and flashings and gives the roof much better wind uplift performance. From the drip edge all the way to the ridge cap, the standing seam is interlocked.
Pole barn metal, because of its design, cannot be hemmed or interlocked. There is not way to bend the roofing panel flat but even if you could the trims are not available. Pole barn metal is a very basic metal roofing system not equipped to water proof many common details found on homes or businesses. Standing seam metal roofing however, is a robust metal roofing system that can water proof virtually any roofing detail out there if the worker has sheet metal training and adequate skill.
Gauge and Paint
3. Kynar Paint and 24 Gauge Steel vs. Siliconized Polyester Paint and 29 Gauge Steel
The third comparison between the standing seam metal and pole barn metal roofing is the thickness of the steel and the grade of paint. Many homeowners make the assumption that pole barn metal is going to last a life time of 50 years, and that it will be the last roof they have to put on. But the thing about 29 gauge steel is what its made of will rust completely through creating pin hole in the roof some where between year 15 and 20. Many of the pole barn metals are formed out of material that is only 29 gauge when you include the thickness of the paint.
Standing seam metal roofing is most commonly made of 24 gauge steel with much higher tensile strength. The much thicker steel equals much longer life and the Kynar paint means that the standing seam roof will not only last, it will still look great as it ages. Kynar paint keeps its color even after years of harsh sun, wind and rain.
Siliconized polyester paint is what is used to give color to pole barn metal and it quickly fades, chalks, and peels leaving the metal roof with poor appearance and greatly diminished curb appeal. We consistently see chalking, peeling, and rust on pole metal years 12 to 18. Kynar paint is guaranteed for 35 years.
If you have made it this far into the article I am sure you are beginning to see why we at Exterior Pro believe that screw down metal has its place on certain types of structures. Mainly barns and storage facilities. And why we believe that standing seam is better fit for homes and businesses with finished interiors and longterm performance and curb appeal in mind. You will spend a little more on a standing seam metal roof but you'll get a lot more value for your money. There are areas and parts of a home where going cheap is not a problem or big deal, we just do not recommend it for your metal roofing. For a free metal roofing quote on your home or business contact us today.