Gilles' Outlet

April 15, 2007

Replacing soffit vents

Filed under: House Remodelling — Gilles @ 11:39 pm

A soffit vent is rebuilt from scratch. An inactive bird nest is discovered and removed from the attic.


Skill Level: 2 (Basic)

Time Taken: About One Hour

Attic ventilation is important. Good ventillation in the attic prevents mold growth, moisture and helps prevent rot.

In this article, we demolish a poorly repaired soffit vent, discover an inactive bird nest and remove it. We build a custom frame out of cedar lumber, staple soffit mesh and install it on the house.

Left: the soffit vent to rebuild.

Clearly, someone did a sloppy job: the vent is half obstructed by what appears to be a ripped piece of 2×4. The mesh is covered with paint restraining most of the airflow.

Right: a lader with wing was used. Working on a ladder is very dangerous. Use common sense and follow the instructions of your ladder’s manufacturer.

And by the way, I cannot be held responsible for anything which may happen to you as a result of reading this blog. Always consult a professional.

Left: I used a flat pry bar to remove the toenailed piece of wood and peeled the mesh.

It was held in place with various fasteners, none of them galvanized. Most were pretty badly rusted. The whole assembly hid an inactive bird nest.

Right: as I peeled more mesh, I noticed a duct discharging close to the vent. That duct was traced back to a bathroom fan.

This is a major problem. This is an intake vent. All moisture extracted by the bathroom fan is immediately carried in the attic by the air entering through the vent. Moisture accumulates in the attic. This is bad. 

This will not be addressed today but it will in a future article.

The mess seen from the attic. I took this picture before removing the soffit block so I knew about the nest and the duct.

The black flexible duct comes from a bathroom fan. It will need to be vented through the roof but this is another story. When this is done, all remaining traces of bird’s nest will be removed.

The vertical pipe on the right is a plumbing vent. It is actually the main stack’s vent.

Back on the soffit side. I removed all unused nails and staples I could using a pair of pliers.

I carefully measured the opening and removed 1/32” on each side to facilitate installation and give the wood some expansion room. It ended up being 22-1/8 x 3-1/2. None of the building supply stores I know about carry such a soffit vent cover so I decided to make my own from scratch.

Left: I cut all pieces to dimension using a power miter saw.

I used 1×2 rough sawn cedar (actual dimensions: 5/8 x 1-1/2). Insects and other rodents dislike cedar oils. It is critical to make the attic very unappealing to birds, insects and other rodents.

Right: I dry fitted all pieces on a flat surface and measured one last time to make sure the box would fit.

Left: I applied a generous bead of waterproof wood glue (rated for exterior applications) to both ends of the longest pieces.


Right: I assembled the frame and clamped it to hold pieces in place as the glue dries.

Left: I drove one hot dipped galvanized common 4d nail in every side of the box. It was easy because the clamp maintained pieces together tightly.


Right: a roll of "kwikmesh" utility screen. It is a 1/8” galvanized mesh specifically designed for soffit vents or foundation vents. It comes in 4” x 25′ rolls.

Left: a piece of mesh was cut to length using a pair of tin snips. I also had to rip about 1/2” of the mesh.

Right: the mesh was stapled to the frame using 18 gauge galvanized narrow crown staples. I used a pneumatic stapler and drove a staple about every inch.

That’s a lot of staples but I really wanted the mesh to stay well attached to the frame. Loose mesh will let insects in and tear more easily under wind pressure.

In general, galvanized fasteners should be used for all exterior applications. Moreover, cedar’s natural preserving oils are highly corrosive and galvanized fasteners (or better stainless steel) must always be used in cedar.

Regular (aka "bright") fasteners will rust very quickly.

The finished frame seen as it will be when installed. The mesh stands at the back of the frame so it is slightly more protected from the weather (not much more).

The yellow mark on the left side is a trace of chalk I have not yet removed.

Left: the frame was positionned in the opening. It fit snuggly.

Right: I fastened the frame to the rafters using one hot dipped galvanized common 4d nail on each side.

Once the vent was installed, I could feel the air getting sucked into the attic through the mesh.

Tools Used:

  • Power Miter Saw 
  • Pneumatic Stapler
  • Clamp
  • Flat Pry Bar
  • Tin Snips
  • Ladder With Wing
  • Basic Carpentry Tools

Materials Used:

  • Cedar 1 X 2 (actual 5/8” x 1-1/2”)
  • Galvanized Soffit Mesh
  • Galvanized Hot Dipped 4d common nails
  • Galvanized 5/8, 18 gauge narrow crown staple
  • Waterproof Wood Glue


Leave a Comment »

No comments yet.

RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

Blog at