Almost every article about attic ventilation tells you the same thing: you need
intake down low, exhaust up high, and air moving between them. Fine. But it skips
the part that actually catches people.
You can have both and have neither.
On a house on Murray Road in Woodstock this spring, we found a roof that passed
every check a homeowner could make from the driveway. Ridge vent along the peak.
Vented soffit running the length of the eaves. Standing in the yard, that roof
breathed.
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It didn’t. And the decking overhead was already telling us so.
Why they called us in the first place
Ventilation was not the reason for the appointment. Woodpeckers were.
Here’s how Skyler Wilborn, our sales consultant and designer, described the house
after running the inspection:
“These homeowners originally found us by just doing research of reputable
contractors near them. They had old cedar siding that was starting to rot, and they
were having lots of issues with woodpeckers. Their siding was original to the home,
about 50 years old. The roof was also older and in bad condition. He also had
concerns about ventilation.”
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That last sentence is the one that mattered. The homeowner had a hunch. He
couldn’t have told you what was wrong, only that something about the attic didn’t
seem right to him.
He was correct twice over.
What the inspection actually found
“They had soffit vents on the exterior, but they were painted over throughout the
years, and so there’s not proper ventilation coming through the soffit. And they did
have ridge vent. But after doing an adequate inspection, there was actually no
opening for the air to exhaust or escape out of. So they physically had one, but
there was actually no opening in the ridge. It was just the two pieces of plywood
meeting each other, so there’s no opening for the air to escape.
I did an attic inspection on both of their attics, and because of the poor
ventilation they were starting to get mold on the decking of the roof.”
Read that again, because it’s two separate failures stacked on top of each other.
The intake was sealed by paint. The exhaust was never opened at all. A ridge vent
had been fastened down over a ridge where nobody had ever cut the decking back. Two
sheets of plywood, meeting at the peak, solid. The vent was a hat sitting on a
closed jar.
Neither condition is visible from the ground. That’s the whole problem.
A ridge vent does nothing without a slot cut beneath it
This is the part most homeowners have never been told. A ridge vent is the
cover for an opening, and the opening is a separate step.
That opening is a slot the roofer cuts through the sheathing along the peak
before the vent goes on.
InspectAPedia’s ridge vent inspection guidance
describes roughly one and a half to two and a half inches of open space on each side
of the ridge board. Manufacturer instructions run tighter than that and they govern:
CertainTeed calls for about three quarters of an inch per side, Benjamin Obdyke
about an inch. Follow the instructions for the vent actually being installed.
The vent then caps the slot so weather stays out and air still gets out.
Skip the cut and you’ve installed roof trim. It looks identical from the street,
and identical from a drone photo, and it will pass a visual roof inspection done
from outside the house. The only way to know is to go into the attic in daylight and
look up at the peak. If the ridge is open, you’ll see a strip of light running along
it.
On Murray Road there was no strip of light. There was plywood.
Painted soffit vents look completely normal from below
The intake side failed differently, and slower.
Vented soffit works through hundreds of small perforations. Every time a house
gets repainted, a little more paint bridges those holes. Enough repaints and they
close over entirely.
From the ground the soffit still reads as vented, because the dimples are still
there in the panel. Up close you find the holes filled in and the surface smooth.
Inspection guidance on blocked soffit vents
suggests running a hand along the soffit and feeling for the flat spots where the
openings should be, and it ties blocked intake directly to condensation, mold and
ice damming in the roof cavity.
So a homeowner looks up, sees vented soffit, and reasonably concludes the intake
is fine. It hasn’t been fine for years.
What the code is actually asking for
Model code sets a minimum on ventilating area rather than on hardware. Under the
International Residential Code,
section
R806.2, the baseline is one square foot of net free ventilating area for every
150 square feet of the space being vented. That drops to 1/300 when specific
conditions are met, and one of those conditions is that between 40 and 50 percent of
the required area sits in the upper portion of the attic, with the balance down
low.
The number worth noticing there is the split, not the ratio.
Code doesn’t ask whether you own a ridge vent. It asks for a working high side
and a working low side, in proportion. A roof with a sealed intake and an unopened
exhaust has neither, no matter what is screwed to it.
One caution: which edition of the IRC applies to you depends on
your municipality, and local amendments vary. Crystal Lake and McHenry County are on
different editions of the residential code. Treat the model code as the floor and
confirm the specifics with your own building department.
How it got fixed
Both ends had to be opened. Replacing the roof alone would have rebuilt the same
sealed system with newer materials, which is worth remembering if you’re
already planning a roof
replacement.
“Also, for the roof, they wanted us to replace all of the plywood because of their
concerns with the mold. … To address the ventilation issue, we cut bigger holes in
the soffit to allow more intake venting, and also we cut back the plywood on the roof
to allow a proper exhaust ventilation, and then installed the ridge vent over it.”
Three steps, in that order, and the second one is the step that had been skipped
the first time around. Enlarge the intake. Cut the decking back at the ridge. Then
set the vent over the slot you just made.
The vent itself was never the missing piece. The opening under it was.
The second thing we found, once the siding came off
Tear-off has a way of answering questions nobody asked.
“For the sheathing of their siding on the exterior, they did not have any plywood
on the house, just foam board backing. So what we did is removed all of the existing
cedar siding and reinstalled over 100 sheets of plywood around the entire thing.”
Wood siding nailed straight over foam board, with no wood structural panel behind
it, was a recognized way of building. Plenty of walls leaned on 1×4 let-in bracing
behind the siding instead.
What that leaves out is racking strength, which is a wall’s resistance to being
pushed sideways by wind.
Forest Products Laboratory research found that
much of a braced wall’s racking strength is owed to the interaction of board sheathing
and let-in bracing, and that no such interaction happens with non-structural foam
sheathing. Let-in bracing on its own provided only about 600 pounds of resistance to
horizontal load.
So sheathing those walls in plywood before the new
siding went on changed what the walls do, not only what they
look like. You simply don’t know any of that is there until the old siding comes off,
which is worth keeping in mind when you’re comparing two bids and one is noticeably
cheaper. What’s behind the old siding isn’t on either proposal.
What the house became
The homeowners had wanted a bigger change than a repair for a while.
“The homeowner was also interested in doing stone or brick on their home, and also
they wanted to replace the entry door, a utility door, and their two patio doors that
were 30+ years old and just starting to wear down. They didn’t look the best and were
not operating properly. So there are multiple projects they’re looking to do, and it’s
a good chance to make a big transformation on the exterior look.”
“Since they are a little bit farther out in the countryside and they have a small
farm with chickens, ducks and a turkey, they wanted to go with a farmhouse-inspired
home, going with red siding, stone, and tan accent trim. I put together a few
different 3-D renderings for them so they can visualize the different styles and
looks. They decided to go with stone across the front side of their home, about four
feet high.”
“So did the red vinyl siding with the tan corners, we did the Versetta Stone.”
This is Woodstock, and it sits near
other work we’ve done in
town. The doors were their own conversation.
“They decided to go with a black entry door from Albany, and also a black Andersen
storm door on the back of the home. Reinstalled two new Andersen 100 Series patio
doors. We also installed a utility door on the back of the home and another Andersen
storm door.
Also, it wasn’t something the homeowner had asked for, but after going over the
options we decided that new garage doors would also greatly improve the look of the
home, so they decided to go with two black garage doors to match the entry doors,
insulated, because they’re thinking about potentially utilizing that space as an
office or workshop in the future.”
Garage doors are something we offer and coordinate rather than hang ourselves. A
partner company does that installation.
“It was a pretty massive transformation. Aesthetically it really boosted the curb
appeal of their home, but also now these homeowners can have peace of mind … that
they no longer have any ventilation issues in their attic or roof.”
All of which is the part you can see. The part that will decide how long the roof
lasts is a strip of open decking at the peak that nobody will ever look at again.
How to check your own attic in about five minutes
You don’t need tools, and you don’t need to walk the roof.
- Go into the attic during the day with the lights off. Let your
eyes adjust for a minute. - Look up at the peak. A working ridge vent shows a continuous
line of daylight along the ridge. Solid wood means the slot was never cut. - Look toward the eaves. You should see daylight at the bottom
edge where the soffit vents are. No light means blocked, either by paint or by
insulation shoved into the rafter bays. - Look at the underside of the decking. Dark staining, streaking,
or frost in winter means moisture is condensing up there. - Feel the air. An attic much hotter and stickier than outside on
a summer afternoon isn’t exchanging air.
If the ridge is dark and the eaves are dark, you have what Murray Road had, and a
new roof by itself won’t change it. That’s one of the questions worth raising before
you sign anything, along with the
other mistakes that
cost people money on a roof replacement.
Questions we get about this
Can a ridge vent be installed without cutting the roof open?
Physically, yes. And that’s exactly the failure we found. The vent fastens to the
peak whether or not a slot was cut through the decking beneath it, and it will look
correct from the ground indefinitely. The cut is what makes it a vent, and it’s the
step that gets skipped.
How do I know if my soffit vents are painted over?
Check from inside the attic first, since it’s faster: no daylight along the eaves
means no intake. From outside, get close enough to see individual perforations. If the
surface reads smooth and the holes look filled in, they’re blocked. Vented soffit can
look normal from the ground for years after paint has sealed it.
Will a new roof fix an attic moisture problem?
Only if ventilation is part of the scope. Shingles don’t ventilate. If the intake
is blocked and the ridge was never opened, a tear-off and re-roof can rebuild the same
sealed assembly with newer materials. Ask any roofer bidding the job what they intend
to do at the ridge and at the soffit specifically.
What does staining on attic decking mean?
It generally points to moisture condensing on the underside of the sheathing rather
than to a roof leak, especially when it’s spread out instead of concentrated in one
spot. What it is and how far it has gone takes an inspection to say. It’s not
something to diagnose from a photo.
Does this only happen to older houses?
Painted-over soffit vents need many repaints to close up, so that failure skews
older. An uncut ridge is an installation error and can be any age, including a roof
replaced recently.
If you want someone to look
We’re in Crystal Lake and we work throughout McHenry County, including Woodstock,
on roofing and siding both. If your attic is showing any of
the signs above, or if you just have the same hunch this homeowner had, an inspection
is the way to find out.
Request an inspection, or call
(815) 356-9020.
