Some roofing projects have one detail that makes them easy to remember. At this Richardson home, it was the full-size Big Boy standing beside the swimming pool, hamburger in hand.
The homeowner has more than one piece of vintage Big Boy restaurant memorabilia, and we had permission to photograph it. Older customers may remember the character from Kip’s Big Boy, while Bob’s Big Boy was the better-known name in other parts of the country.
The roof itself also had something worth discussing. Before installing the new shingles, we needed to address the home’s original wide-board roof decking.
An Attic Inspection Confirmed 1×8 Plank Decking
From our initial roof inspection, we suspected the house had older dimensional-lumber decking rather than plywood or OSB. An inspection from inside the attic confirmed that the roof was decked with 1×8 boards.
This type of roof deck is common on older homes, but it is not the nailing surface we would choose for a new asphalt shingle roof today.
Wide boards such as 1×8s and 1×10s can move considerably over time. They can cup or curl, and normal drying and shrinkage can leave gaps between individual boards. That creates an inconsistent surface for fastening shingles.
The boards on this house were not simply torn out. Instead, we installed 1/2-inch OSB over the existing decking to create a continuous, uniform nailing surface for the new roof.
The material order included 112 sheets of 1/2-inch OSB, making this essentially a full overlay rather than a few isolated decking repairs.
Why Put OSB Over an Existing Plank Roof Deck?
If the original dimensional-lumber decking is still structurally sound, overlaying it can make more sense than removing all of it.
The OSB covers gaps between the old boards and gives the roofer a consistent surface for fastening the shingles. It also helps eliminate some of the irregularities that can develop as individual boards move over the years.
The shingles are only one part of a roofing system. The surface underneath them matters just as much, particularly when it comes to proper nail placement.
Can you install shingles directly over 1×8 roof decking?
It depends on the condition of the decking.
Wide plank decking can shrink, cup and develop gaps. Those conditions can make it difficult to consistently fasten every shingle into solid wood. The deck should be evaluated rather than assuming that an older plank roof is automatically suitable for a new shingle installation.
On this house, we elected to overlay the 1×8 decking with 1/2-inch OSB.
Does the old plank decking have to be removed?
Not necessarily.
If the existing lumber remains structurally sound, it can often stay in place while plywood or OSB is installed over it. That provides a better nailing surface without unnecessarily removing the original roof structure.
Why are gaps in roof decking a problem?
A roofing nail needs something solid to hold onto.
With individual plank decking, a nail can occasionally land in a gap between boards rather than solid lumber. A continuous plywood or OSB surface makes proper fastening much more predictable.
Installing a GAF ArmorShield II Class 4 Roof
Once the decking work was complete, we installed GAF ArmorShield II impact-resistant shingles in Charcoal.
ArmorShield II is a UL 2218 Class 4 impact-resistant shingle. The roofing system also included GAF starter shingles, synthetic underlayment, ice-and-water protection and impact-resistant ridge shingles.
Class 4 is the highest classification under the UL 2218 impact test. That does not make a roof hail-proof. Large enough hail can damage virtually any asphalt roof. The purpose is to provide better impact resistance than a conventional asphalt shingle.
That can make a Class 4 roof worth considering in North Texas, where hail is one of the major reasons roofs are replaced before reaching the end of their normal service life.
Some insurance companies also offer discounts for qualifying impact-resistant roofing products. State Farm, for example, has a roofing certification specifically addressing qualifying Class 3 and Class 4 products. Actual eligibility and premium savings depend on the individual carrier and policy.
Protecting the Pool and the Rest of the Property
The roof was only part of what needed protection during this project.
The backyard included a swimming pool, landscaping, outdoor furniture and the homeowner’s collection of vintage restaurant memorabilia. Our project notes specifically called for protecting the pool during the roof replacement.
A tear-off produces old shingles, granules, nails and other debris. Around a property like this, preparation before the first shingle comes off is particularly important.
Our CompanyCam photos documented the property before the work started, the decking and roofing work as it progressed, and the finished roof afterward. They also happened to document one of the more unusual spectators we’ve had on a roofing job: Big Boy beside the pool.
A Better Roofing Surface Before the New Shingles Went On
The Class 4 shingles are the part of this Richardson roof replacement that you can see from the street.
The OSB underneath them may be the more important improvement.
By inspecting the attic and confirming the existing 1×8 plank decking before the roof replacement, we were able to address the nailing surface rather than simply installing new shingles over whatever was already there. The 1/2-inch OSB overlay gave the new roofing system a flat, continuous and dependable surface.
And when the job was finished, Big Boy was still standing beside the pool holding his hamburger.
