Bird block vents are wood blocks fitted between the rafters at the top of the exterior wall, with screened holes or slots that let outside air into the attic while keeping birds out. On homes with open eaves or exposed rafter tails, they are often the attic's main intake vents, so when they fail, the whole ventilation system suffers.
If you are unsure whether your attic is getting enough air, call Cannon Roofing at (940) 627-1045, any time, or use our contact page to book a free inspection of your roof and attic.
What bird blocks are and where you find them
Look at the underside of your eaves. If you see exposed rafter tails and a board or panel between each pair of rafters, right where they cross the wall, those are bird blocks. Solid blocks close the space; vented blocks have round holes, slots or a screened opening. They are common on older homes, on houses with an open-eave style and on many barns and shops around Wise County.
Homes with boxed eaves and panel soffit usually rely on soffit vents instead. Some have both, with blocking behind the soffit that may or may not be vented.
From the ground, vented blocks often look like a row of small screened rectangles or circles tucked against the wall line. If you cannot tell, a flashlight and binoculars on a bright afternoon will usually show whether the openings are clear or sealed shut.
How bird block vents provide intake
Attic ventilation depends on air entering low and leaving high. Each rafter bay is a channel. Vented bird blocks let outside air into the bottom of each bay, and it rises along the underside of the roof deck to exhaust vents near the ridge. Because there is a block in every bay, air enters evenly along the whole wall, which is exactly what good intake should do.
In a North Texas summer, that steady air movement keeps the underside of the roof deck from holding heat long after sunset. Without it, shingles bake from below and the air conditioner fights a hot ceiling. In winter, the same airflow carries off moisture rising from the living space before it can condense on cold nails and decking.
How much intake your attic needs depends on its size and the amount of exhaust venting. Our article on how much attic ventilation your roof needs walks through the balance.
Common bird block failures
Bird blocks are simple, but several things quietly shut them down.
Painted over
Screens and small holes get sealed by layers of exterior paint. From the ground the blocks look vented, but little or no air gets through. A wire brush may reopen some, but thick paint often means the screens should be replaced.
Blocked by insulation
Blown insulation piled against the back of the blocks, or batts pushed tight to the roof deck at the wall, close the air path from inside. Without baffles to hold a channel open, the vents feed into a wall of insulation.
Damaged screens and pests
Torn screens or blocks with holes chewed larger invite birds, wasps and rodents into the attic. Rot at the bottom of the block from roof leaks or overflowing gutters can open gaps too.
Solid blocks where vents should be
Previous repairs sometimes replace vented blocks with solid ones, or cover them to keep pests out. The attic loses intake, and the roof and upstairs rooms get hotter in a Texas summer. Our guide to attic ventilation problems in Texas lists the warning signs.
Upgrades worth making during a reroof
A roof replacement is the best time to fix intake, because the roof edge is open and the crew is already working at the eaves.
- Replace rotted or damaged blocks and screens.
- Swap solid blocks for vented ones where the bay opens into the attic.
- Add baffles in each bay so insulation cannot block the path.
- Match intake to the new exhaust, such as a ridge vent, so the system is balanced.
- Consider other intake options, like vented drip edge or edge intake vents, when bird blocks alone cannot supply enough air.
What we check before recommending changes
We look from the ground, from the attic and from the roof: how many bays are vented, whether air can reach the deck, what exhaust is in place, and whether there are signs of heat or moisture problems such as brittle shingles, stained decking or rusty nails.
Getting it right with Cannon Roofing
Ventilation is part of every roof we inspect and replace. Through our roofing services, including roof replacement, we can repair or replace bird blocks, open up intake and balance it with exhaust. Cannon Roofing has served Decatur and North Texas since 1994, our crews are factory trained, and every crew member holds the Technician Seal of Safety. Our inspections look at intake, exhaust and the attic itself, and we explain what we find in plain terms before recommending any work. Call (940) 627-1045 to book an attic and eave check.
Frequently asked questions
Can I clean painted-over bird block vents myself?
If the blocks are reachable safely from a ladder, sometimes. Many need screens or blocks replaced, and the inside still has to be clear of insulation to work.
Are bird block vents enough intake on their own?
Sometimes. Each block has limited open area, so it depends on how many bays are vented, how clear the openings are and how much exhaust the roof has. We measure intake against exhaust to confirm.
Should bird blocks be replaced during a new roof?
Damaged, rotted or solid blocks that should be vented are best handled during a reroof, when the eaves are already accessible.
Want your attic breathing properly? Call Cannon Roofing at (940) 627-1045, day or night. We will inspect the eaves, attic and exhaust vents and give you a free estimate. You can also send details through our contact page.