Is it time for a roof replacement? Do you know what kind of wood you have under your roof shingles?
Roof decking is the base layer of your roof. It keeps things structurally sound and provides a clean foundation for your roofing materials. Today, the standard practice is to use OSB boards. But homeowners can request plywood, plywood roof sheathing, or roof decking plywood.
Dimensional lumber was most often used before the World War II building boom. Which can pose challenges under today's modern roofing standards.
Still, we see dimensional lumber roof decking all the time. We also see the challenges homeowners run into when their roof still has dimensional lumber underneath during a replacement.
Here, you’ll learn what dimensional decking is, why it often fails, what replacing it involves, and how much it can cost to re-deck your roof.
Let’s get started.
What is Dimensional Roof Decking?
Dimensional roof decking is an older building method where the roof deck is made from individual wooden boards. The boards can vary in size, but are typically 1x4, 1x6, or 1x8, and are installed across the rafters.
It’s most common on older homes throughout the Myrtle Beach area, as roof decking does not always need to be replaced at the time of a roof replacement. That is, until it starts failing.
OSB is less likely to fail, which is what modern roofers install today (unless you request plywood). OSB, or an Oriented Strand Board, is an engineered wood panel made from compressed wood strands and resin. Because of how it’s made, it’s less likely to crack over time than dimensional lumber decking.
Why Does Dimensional Roof Decking Often Need Replacement?
Since modern homes no longer use dimensional lumber for roof decking, chances are your older home’s decking has weakened over the years, particularly after multiple roof replacements.
Most older homes have had at least three or four roofs installed over its lifetime. With every new roof, nails are removed and reinstalled, and your roof deck takes the brunt of it all.
Over time, this creates:
- Loose nail holes: Any holes in your roof have the potential to leak, even if the materials are re-applied correctly.
- Cracked or broken boards: This can occur because of multiple roof replacements, or because of wear and tear. Any opening from your roof deck, leaves the potential for leaks.
- Missing knots that leave open holes:
Because dimensional lumber decking is made from real lumber, it can have imperfections. So, it’s fairly common to see big holes in dimensional lumber decking that were caused by knots coming loose. - Gaps between dimensional lumber decking: If the dimensional lumber on your roof is not sitting snug together, gaps can cause a problem when you get a new roof. A trustworthy roofing contractor will tell you this ahead of time. This is a big deal, because your roofing material is nailed to your home. If a nail has nothing to grab onto, the materials the nail was holding onto your roof will fail or fall off prematurely.
All of these issues can void your warranty and leave you with the bill for repairs on damage caused by these problems. To learn more about what can void your roof warranty, check out this article: What Voids a Roof Warranty?
Even if your shingles are new and installed correctly, dimensional lumber roof decking can sabotage it, making dimensional lumber a liability. These days, modern building codes require roof materials to be attached to a solidly sheathed deck, and unfortunately, old dimensional lumber decking can no longer cut it.
So, what do you do if you have a dimensional lumber roof deck? Can it be removed and replaced?
What is the Process to Remove Dimensional Roof Decking?
While you can remove dimensional lumber roof decking, it’s almost never removed during a modern-day roof replacement.
Why?
Because pulling up every board is extremely labor intensive, often raising the cost of your roof replacement very significantly.
Not only that, but it simply might not be necessary. Instead, roofing contractors will “re-deck” the roof, by simply installing OSB boards over the dimensional lumber. This gives your roofer a clean slate to work with, without holes or cracks.
To get an idea of what a regular roof replacement might cost, take a look at this article: How Much Does a Shingle Roof Cost? Here, you'll learn all the details on the average roof replacement cost, so you know the base
How Much Does it Cost to Re-Deck a Dimensional Lumber Roof?
Most Myrtle Beach homeowners want one thing: a real number, not a vague range.
Here it is.
For the average 20-square roof ($2,000 sq. ft), re-decking costs $4,000 to $5,000.
This price includes:
OSB materials: Your roofer will need to purchase enough boards to cover the dimensional lumber, this number can vary depending on how large your roof is. Roof decking is not commonly included in your estimated roof price because it’s not something that would normally be replaced unless it was compromised. - Roofing nails: While small, a significant number of additional nails will be used to re-deck your home, which is why they are included in the price.
- Labor: Completely re-decking a home is not common practice for a regular roof replacement. But in the instance that you have dimensional lumber decking, there are additional costs for the labor involved in re-decking. It takes a considerable amount of time to re-deck a home, increasing the price.
Roofs with steep pitches or extensive board damage may cost more, but this range covers the most common homes we see along the Grand Strand.
How Do You Know if You Have Dimensional Roof Decking?
You can find out in 30 seconds.
Just look inside your attic. If you have dimensional decking, you’ll see row after row of long wooden boards spanning the length of your roof. Each plank will be either 1x4, 1x6, or 1x8.
You may even see some of the issues we’ve covered in this article. If you see wooden boards instead of full sheets, you’re almost certainly dealing with dimensional lumber roof decking.
But if you're unsure, you can always schedule a roof inspection with a trusted roofer.
FAQs About Dimensional Lumber Roof Decking
Q: Can I install new shingles directly over dimensional lumber without redecking?
You could..but it’s risky. If the nails don’t hit solid wood, leaks are almost guaranteed over time. This is why some roofing contractors may refuse to roof over dimensional lumber.
Q: Will insurance cover re-decking my roof?
Often yes, especially because the decking doesn’t meet today’s requirement for a solidly sheathed surface. But it’s important to note that coverage can vary based on your insurance policy. To learn more about the two policy types you could have, check out this article: ACV vs. RCV: What is the Best Type of Homeowners Insurance for a Roof?
Q: Is removing the old boards better than installing OSB over them?
Full removal is possible but much more expensive. Installing OSB over the boards is the industry standard and meets modern code. Installing OSB over a dimensional lumber roof deck will not compromise the integrity of your roof in any way.
Q: Does this only affect older homes?
Yes. Homes built after the early 2000s almost always have OSB or plywood and will not have dimensional lumber.
Best Way to Replace Dimensional Roof Decking
When elements of an older home start to fail, it can be very stressful to bring it up to today’s building standards. And while a dimensional lumber roof deck is solid, it can deteriorate over time, leaving you with plenty of questions.
The bottom line is, if you have dimensional roof decking, the roofer you choose should have a set plan in place to ensure your roof is strong for many years to come. Here, at Linta Roofing, we install OSB over dimensional lumber roof decking. We do this because it ensures the quality you expect from us and doesn’t mess with your warranty.
If you have any questions about that process, don’t hesitate to contact us. We’re happy to walk you through the process step-by-step and work with you along the way to give you the best new roof possible.
