Solving a new gable end vent puzzle…without a ladder
Sometimes it’s the little jobs that allow us to flex our ingenuity muscle more than the big jobs.
We were just finishing up a bit of messy work on some foundation waterproofing for a client when they mentioned that they were also getting some leaks into the gable end of their attic. I looked up at the 35-foot-tall brick gable-end wall and could barely see the ratty wooden vent from below, but it seemed like the likely culprit.
While we were eager for some cleaner work, I knew repairing this puppy from the outside would be no picnic. So I said, “Let’s take a look in the attic and see what we can do.”
From inside the attic it was easy to see that the brick and block of the gable end were run up around the form of a combination circular/orthogonal vent. This was typical new construction. Installing retrofit pieces would pose a geometric puzzle. The simplest solution to this puzzle would involve cellular PVC, Festool dominoes, Kreg pocket screws, and (best of all) no ladders.
Here’s how we went about it.
Studying the old unit for replication and improvements
The original unit (see photo, right) practically crumbled out of its existing masonry opening. Demo from the inside was a piece of cake, and we brought the unit back to the shop. I measured the outside diameter at exactly 28 in.
This turns out to be a fairly stock unit, and is still widely available, but it’s built mostly from finger-jointed sugar pine. I wanted our new vent to last much longer than the original, yet I felt obligated to match all outside and visible profiles exactly—after all, this was an historic district.
The one small concession I made to changing the outside look of the original vent was adding one extra louver, which helped prevent windblown storm rain from bouncing inside the attic. No one from the neighborhood could possibly pick up this ‘before and after’ change; they’d have to have one heck of a visual memory!
New materials and tools allow better ingenuity
The solution I came up with in order to improve the durability of the new vent, and work a finished installation from the inside, consisted primarily of four key design aspects:
- Building two frames on the inside of the radius work, whereas the original only had one. This would allow for a secondary louvered rectangular assembly to nest inside a primary rectangular frame. Since the primary frame could be locked together securely to the exterior brick mold with a few stainless steel pocket screws from the inside, this solved the geometric puzzle of fitting two different shapes into two different existing masonry openings. A secondary panel was the only way to avoid the problem of fitting louvers into the primary frame on-site. This would have been more troublesome than in a shop, and probably would have involved touch-up paint and caulk from the outside on a 40-ft. ladder.
- Improving drainage to secondary louvered frame panel by fitting flashing ‘blocks’ or ‘diverters’ between the lower half of the vent slats, which allows rain to drain quickly toward the exterior. The need to install flashing blocks was another reason I didn’t want to fit louvers in the primary frame on-site.
- Constructing everything from cellular PVC, due to its workability and weather-resistant characteristics. Also, the quick set times of PVC glue allowed us to speed up the process of millwork, and gave us very strong and reliable bonds in our laminations and joints.
- Installing a replaceable screen to the primary frame, thereby allowing the secondary frame to be captured and ‘float’ within its nesting place without mechanical fasteners or glue. Having southern exposure, I felt the more massive secondary PVC louvered frame of this vent could potentially expand and contract much differently from the primary frame. I didn’t want it transferring stress to the primary radius work and/or stress the caulk seals. I felt a snug secondary frame fit and an overlapping screen lock were the best choice for this situation.
Getting to work in the shop; radius and primary frame work
We started by working off of a scrap of 3/4-in. AC plywood. This provided a good sacrificial base upon which we could fasten multiple layers of PVC flat stock, all with mitered corners. The plywood base was large enough to accommodate the complete width of the finished radius profile.
The brick mold thickness was built up from laminations of 1/2-in.-thick stock on top of 3/4-in.-thick stock with off-set joints. We used regular PVC glue to laminate the layers and Festool dominoes to reinforce the joints. Layers were clamped tightly together using screws that were placed outside the profile and into the sacrificial base (see photo, right).
We placed dominoes in areas that would be buried in the finished brick mold profile, which meant they would not be exposed or ‘revealed’ during the milling phase.
Finally, we padded up our center trammel point with plywood scraps to be flush with the top layer, and worked our router from outside in, and top down.
The sacrificial base allowed us to rout the profile all the way through without cutting into our workbench. There was a 3/4-in. brick mold backer that was routed separately, glued (with PVC glue), and clamped to the brick mold profile, to give full profile to the inside radius. It was roughed-out from an octagonal glue-up (again with dominoes at joints).
Since this backer had to fit and register inside the back of the louvered outer frame, it was not the full outside radius. This was one of the trickier parts to make and attach. Again, to avoid on-site fitting, I used the old vent as a pattern, because we knew that fit!
Secondary louvered frame
While I worked radius profiles, my helper milled the PVC stock to size, and assembled the secondary louvered frame. All frame and louver components were glued with PVC glue and/or pocket screwed with stainless steel pocket screws. There were no components that would prematurely rust or rot.
Since the inside louver shape is bigger than the circular brick mold, rain water can get behind the perimeter edge at the lower half of louver. In fact, frequent water penetration on the old unit led to its failure. To improve the design, I glued filler blocks between the fins just on the outside edge of radius (and out of view). This serves to divert water down to next lower fin.
I shaved down the excess filler easily with my FEIN multi-master, and sanded it smooth. All water now drains by gravity down to the bottom of the circular trim and vacates at the exterior brick face of the building’s envelope.
Had this new louvered piece been made from wood, I would not have been so confident installing wood ‘deflection’ blocks in this manner, due to the effects of wood fiber expansion and contraction, resulting in stress across the glue joint. However, only having to overcome limited thermal expansion and contraction stress across the glue joint, I felt PVC was a good choice for a detail like this.
You will later see the ‘notch’ in the exterior brick molding that serves as the final evacuation point for any accumulating moisture on the bottom of the brick molding.
Finishing up in the shop
In the photo to the right, you can see all three components of the louvered vent, as a bird would see it from the outside. Note the ‘diverter’ blocks on the vent panel (in back) and drain notches on the bottom of the primary circular brick mold unit. More on the drain notches below.
We painted the finished components (only exterior exposed surfaces) in the shop with three coats of quality exterior latex acrylic paint (Sherwin Williams “Duration”) using High Volume/Low Pressure (HVLP) spray equipment. Spraying is faster, and gives a very even coat; particularly on material like PVC, which doesn’t soak up a paint film like wood, and can often show brush marks.
Some may note that milled PVC is a rougher surface when you expose interior ‘grain’ through the milling process. For this project, where the finished piece is thirty-five feet in the air, we felt nobody would notice; plus, we felt the roughness allowed a better mechanical bond for the paint. If we wanted a smoother finish (say, for a more visible condition) we would have used a couple coats of primer and sanded between coats (in order to fill low spots of pours), and then sprayed the finish coats.
Since we previously pulled the old unit into the shop to use as a reference model, we only had to remove a temporary plywood panel from the rough opening before installing our new, three-stage unit.
The nesting detail is what made this whole thing workable from inside the attic. The inside frame was pocket-screwed with eight stainless steel screws to the outside circular brick mold. I used a close pair of stainless steel pocket screws (rather than a single at each location) to provide another level of security and insurance, preventing the radius work from ever wanting to jump out of the hole and leave home. Because of the different geometry within the planes of exposed brick and rough block, these screws lock the whole assembly in the hole mechanically and geometrically.
The outside radius was fully caulked and sealed to the brick with matching exterior grade caulk. This may look like I climbed a ladder and took this shot, but I was not that brave. This was about 35 feet off the ground, and since I designed this thing to be installed without taking that risk, I merely stuck my camera outside and shot back towards the work.
|Next, I installed the secondary louvered frame, which fits perfectly inside the primary frame, and is screwed to the exterior circular brick mold.|
Below, you can see the freshly re-mortared primary frame within the rough block opening. There is no way rain water can get inside this well-detailed vent. I also suspect that it will remain this way for a very, very long time.
I can tell you that the clients were very pleased with us fixing this annoying leak in their attic with a quality solution. And we were pleased to safely walk away from this job without ever having to scale our 40-ft. ladder.
• • •
I began my building career apprenticing for a master carpenter at age 14. This was after school hours, remodeling homes in historic Clifton, Va. I can still remember my first project—a lattice surround for an air conditioning condenser. Not the most glamorous project; but a nice start. I think my mentor, Louis McFatridge, thought it was a good (and safe) idea to test me on something outside, and seemingly inconsequential. However, since the condenser was on the home’s approach (thus the lattice), I knew all guests would see it. So I took the opportunity (and my mentor’s best chisels) and set out to make it the best lattice surround I could fabricate with my limited skills and knowledge. It was not a masterpiece, but it must’ve turned out pretty darn well because I stayed on with him during the next four summers, up until college. Even during college I got on with any framing or trim crew I could find that would hire me, during holiday breaks and summer recesses. As a designer, this early, and regular, hands-on experience proved invaluable.
I love the design-and-build process, and never consider anything completely perfect. It can always be better. In fact, I earned my bachelors of Architecture degree at Virginia Tech specifically to become a better builder. I started my own design/build company, Vice Versa Builders, in 1993. We specialize in residential remodeling.
I have been truly blessed to be able to do what I love, and love what I do. For me, architecture is problem-solving, with an artistic mindset. Masterpieces are achieved through classical and romantic building elements, living (and aging) in harmony. I always try to keep in mind the advice I give my clients: “Every good solution is preceded by a well defined problem.” Since remodeling problems are usually unique, my goal is to learn, define, and study the specific problems. Then I look to frame the building solution within a harmonic construct that strives for architectural perfection. After 30 years, I’ve been at it quite a while now, and I’m still looking to achieve my architectural masterpiece in every project I take on.