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Roof Deck Rot and Soft Spots on the Oregon Coast: How It Starts and How We Fix It
One of the harder things about roof deck damage is that you usually do not know it is there.
From the driveway, the roof might look fine. Inside the house, there may not be a ceiling
stain. Then somebody gets up there for an inspection, or we start tearing off an old roof,
and there it is. A section of plywood that feels soft, looks dark, or has started separating.
We see this quite a bit on the Oregon Coast.
We are Hardesty Roof Replacement, serving homeowners from Lincoln City to Arch Cape. After more than 20 years working on roofs in this weather, we have learned that the soft spot is usually not the whole problem.
The real question is what made that wood stay wet long enough to weaken.
If we replace the damaged piece but leave the leak, drainage issue, or moisture problem
alone, we are just covering up the reason it happened.
What Is Under Your Shingles Anyway?
Under your shingles or metal roofing is a solid layer of wood called the roof deck.
On most homes, that means plywood or oriented strand board.
That decking gives the rest of the roofing system something solid to attach to. Your
underlayment goes over it. Your shingles or metal roof go over that. Flashing, vents, and
the rest of the system all depend on that base being solid.
Most homeowners never see it.
And honestly, that is normally a good thing.
The trouble starts when water gets through the roofing system or moisture builds up
underneath and the decking stays wet.
How Does Roof Decking Start to Rot?
Usually, slowly.
Wood can get wet and dry out without falling apart. What causes trouble is repeated
moisture or a section that never really gets a chance to dry.
APA, The Engineered Wood Association, explains that long periods of high moisture can
eventually create the conditions for wood decay.
On the coast, we usually find that moisture came from one of a few places.
A Little Leak That Has Been There for a While
This is probably the most common.
Maybe the flashing around a chimney has a small gap. Maybe an old pipe boot cracked.
Maybe water has been working its way through a valley or around a skylight.
The leak might not be big enough to drip into the living room.
Instead, it wets the same section of decking every time the weather gets bad.
That can go on for a surprisingly long time.
By the time there is a visible stain inside the house, the wood above it may already be
soft.
Our roof flashing problems guide goes into the places where we commonly find those
leaks.
Rain That Only Gets In When the Wind Is Blowing
This is another one we see all the time.
Normal rain comes and the house stays dry. Then a real coastal storm rolls through and
suddenly there is moisture in the attic.
That is because wind can push rain into areas that normally shed water just fine.
A shingle edge might lift. Flashing may have a tiny opening. Water can get driven into a
roof transition from an angle it normally never sees.
If your roof seems to leak only when the weather gets nasty, take a look at our wind
Moisture From Inside the House
This one surprises people.
Sometimes the roof is not leaking at all.
Warm air from inside the home gets into the attic, hits the colder underside of the roof
deck, and moisture starts forming there.
Bathroom fans that empty into the attic, poor ventilation, blocked soffits, and high indoor
humidity can all play a part.
That is why, when we find damaged decking, we do not just look at the shingles. We also
want to know what is happening underneath.
Where We Tend to Find Soft Spots
There are certain areas of a roof where we expect to look a little harder.
Valleys are one because they move a lot of water and collect debris.
Chimneys and skylights are another because they rely heavily on flashing.
Pipe vents are common too. Once the rubber around an older vent starts cracking, small
amounts of water can sneak in every time it rains.
Roof edges can also be a problem, especially if gutters have been overflowing or water
has been getting behind the fascia.
It does not mean all of those areas will have damage.
It just means they are good places to start looking.
What Does a Soft Roof Deck Look Like?
Sometimes you can actually see it from the ground.
A section of the roof may look a little lower than everything around it. The shingles might
have a wavy look because the wood below them is no longer flat.
From the attic, you might notice dark wood, old water trails, swollen plywood, or an area
that just looks different from the rest.
Other signs can include:
A sagging section of roof
A leak that keeps coming back in the same place
Dark staining in the attic
Wet insulation
A musty smell
Shingles that no longer sit flat
Rot around the fascia or soffit
Water marks near vents or chimneys
One thing we do not recommend is walking around on the roof trying to find the soft
spot yourself.
If the decking is bad enough, that can turn dangerous quickly.
Does Wet Decking Always Have to Come Out?
No.
This is where people sometimes assume the worst.
Wood getting wet does not automatically mean it is ruined.
APA notes that structural panels can sometimes get wet and still remain usable once
they dry, depending on how much moisture they were exposed to and how long it lasted.
What matters is what condition the decking is actually in.
If it dries out and stays solid, flat, and strong, it may be perfectly usable.
If we can press into it, the layers are separating, the wood is swollen, or there is obvious
decay, that section needs to be dealt with.
Why We Will Not Cover Rotten Wood With a New Roof
A new roof needs something solid underneath it.
If the decking is soft, nails and fasteners do not have the same holding power. Putting
new shingles over bad wood might make everything look good for a while, but the
problem is still underneath.
That is not the kind of surprise anybody wants after paying for a new roof.
When we perform a residential roof replacement, the old roofing comes off and the
decking gets looked at before the new system is installed.
That is usually when the hidden spots finally show themselves.
How We Fix Damaged Roof Decking
Once the roof is open, things become a lot clearer.
We figure out how far the damaged area goes and remove the wood that is no longer
solid.
New decking goes in with proper support and fastening.
But that is only half of the repair.
We also need to correct whatever got the wood wet.
That may mean replacing flashing, fixing a vent boot, correcting a roof edge, dealing
with drainage, or repairing another leak point.
APA makes the same basic point in its guidance about wood decay. Moisture has to be
controlled if you want the problem to stay gone.
Does a Soft Spot Mean the Whole Roof Needs to Be
Replaced?
Not necessarily.
If we find one damaged area and the rest of the roof is still in good shape, it may be a
fairly focused repair.
If we start finding soft decking in several areas, old leaks, worn shingles, and other
problems at the same time, that is when replacement starts becoming a more practical
conversation.
There is a point where opening one section after another stops making much sense.
Our Roof Repair Versus Roof Replacement Guide explains how we look at that decision.
If water is coming into the house right now, visit our Emergency Roofing Services.
Roof Deck Rot FAQs
Does a soft spot always mean rotten wood?
No. The decking may be swollen, damaged, or weakened without being completely
rotten. We need to see the condition of the wood before making that call.
Can you replace just one section of roof decking?
Yes. If the damage is limited to one area, we can often replace that section without
replacing all of the decking.
Can the decking rot without the ceiling ever leaking?
Absolutely. A small amount of water can keep wetting the same piece of decking without
ever creating enough of a leak to reach the ceiling.
Can you put new shingles over soft decking?
We do not recommend it. The new roof needs solid decking underneath so the fasteners
have something strong to hold onto.
How do I keep this from happening?
Take care of leaks early. Keep gutters and valleys clear. Pay attention to flashing and
vents. And if the attic smells damp or you see staining, do not wait until water reaches
the ceiling.
Think You Have a Soft Spot in Your Roof?
A soft spot does not automatically mean you need a whole new roof.
It does mean there is a reason that section weakened, and we want to find that reason
before the damage gets bigger.
Hardesty Roof Replacement serves homeowners throughout Tillamook County and the
Oregon Coast, from Lincoln City to Arch Cape.
We can inspect the roof, attic, flashing, and damaged area, show you what we find, and
explain what actually needs to be done.
If the roof is actively leaking or you notice sudden sagging, visit our Emergency Roofing
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