Insulating a Home Bump Out and a Porch Soffit

Introduction: Insulating a Home Bump Out and a Porch Soffit

My lovely girlfriend had a very drafty bedroom. Key word: HAD. That's before I did something about it. But, the biggest impetus for doing a weekend long project (that lingered a few days after).... SQUIRRELS. Rats with fluffy tails. They were getting into the porch soffit, then into the house. They would scurry around the ceiling at night. If you are familiar with west Philly (where the Fresh Prince is from), you know about this menaces. We decided to DIY a squirrel proofing, air sealing, and insulating project.

Note: The squirrels have found a second way in since this project. They got in in the top of the second floor ceiling, the roof. We got a contractor with a 40 ft ladder to seal the top cornices around the house. A future project will be removing the cornice aluminum cover and air sealing/ insulating every opening in this method. Another goal of this project will be to seal the openings in hopes of getting blown-in insulation in the future. Without sealing, squirrels have a lot of bed material to play with, and the air above the blown in insulation would be even colder.

Step 1: The Porch Soffit

Looking at the porch and the bump out above, I knew the joists to support the bottom of the bump out were cantilevered perpendicular to the other joists. My assumption was that if 1/3 of the joist stuck out past the brick, then 2/3 was inside. This created a deep alleyway for the squirrels to penetrate in. Then, after getting so far, if there were any large holes (i.e. pipes, wires, etc.) the squirrels then had a maze to go through... or chew a new way through.

While walking her dog, I saw one house in the neighborhood with the porch ceiling. I saw the three sided bump out and then had a great idea of what I'd find above our porch ceiling. That led me to my illustration in pen to explain how the squirrels were getting in, and the huge air gap that was directly under the floor. If the gap in between each joist was 16" wide and 2 inches tall, then there was a potential gap (provided 4 spaces between joists) to be 4 spaces * 2 inches * 16 inches. That's 128 square inches. To put that in perspective, it'd be 11.3 x 11.3 inches. That's like a window being open significantly in the window with little cover on top.

Step 2: Disassembly

I began to take down the tongue and groove ceiling. It was light pine wood, that once I got one end pried off, I could pull it down and the other end would lever its nails out. Looking up at the bump out inside the soffit, it was gridded with the support joists and cross bracing. What surprised me is that I was looking at the tongue and groove bedroom floor. In between boards and where radiator pipes went to, I saw carpet. If the carpet had a cut, like near the radiator pipe, I saw the bedroom light. I could clearly see into the house, most bricks were loose and crumbled. Up here in the soffit I could see that all of the neighbors porch ceilings were all connected. Not pictured, the neighbor's soffit had a mummified squirrel.

Step 3: Sealing

The brick showed almost exactly the gap I predicted, a gap about 2 inches tall. Most of the brick mortar crumbled, and the bricks fell off or weren't there. I first tried to mortar in the bricks and skim coat. It wasn't working well. I had limited space to place bricks, and then resulted in not having enough bricks. I covered the opening with a 2 x 10 inch pressure treated dimensional lumber. I spray foamed and caulked the gaps and cracks. I had left over mortar that was drying. I quick skim coated the lumber just for the sake of getting rid of it. I also figured it'd be a dry and nasty layer for a rodent to bite if they got through any foam insulation.

Next, I cut 2" thick polyisocyanurate board to fit into each piece of the bump out's structural grid. I use a spray foam gun to seal the gaps around each piece of insulation. I made sure to butt the sides of the foam board up tight. Poly iso has a R value of 6 per inch, so an R value of 2 was obtained. This had a double faced reflective barrier, which I'm sure helps. I was very liberal with spray foam. I bought so much, that I used it for every thing. I put a bead in between each tongue and groove board I saw on the inside of the soffit ceiling.

Step 4: Sealing It Back Up

I put plywood on the porch ceiling. There was a vinyl cover as well that I didn't take pictures of in the beginning. Due to all the up and down on the ladder and work, I didn't take many pictures. I haven't put the vinyl siding back up yet. We did this project in September, and it is now December. It's still a little drafty, but this made a huge improvement. With just the plywood up, I can easily access the inside this spring if the foam really needs to be doubled up. Knowing how big of gaps there were, the next target is the second story cornices and other bump outs. Old homes in Philly and elsewhere relied on cheap heating 100 years ago. They weren't well sealed, or became unsealed over the years. My foam gun is around almost every project I do. I have sealed so many interior joists, this project gave me the chance to seal it from the outside.

Big key: We drove all the squirrels out with noise and hitting on the ceiling before sealing anything.

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