New Trim Fit for an Old House

When I bought my 1926 Sears kit house in 2011, I was mentally prepared for dealing with the perils and pitfalls that come with owning an old house, and confident in my ability to tackle any major challenges. What I didn’t anticipate—and something that owners of newer houses don’t usually understand—is the feeling of responsibility that came with every design decision I made. I was the new caretaker of a house that had been occupied by only one family since it was built 90 years earlier, and which had clearly been handled with extreme respect. So, when I decided to add a covered porch to the back, I wanted to make sure it would be a good fit for the house. Having seen a lot of bad entries, porches, and additions over the years, I was concerned about ending up with something that looked like a thoughtless bolt-on. I was determined to make the porch look like it had been there all along.

I knew the best way to tie the new porch into the old house would be to make it match. By simply extending each element of the existing trim package to include the porch (or extending them onto the porch), it would appear as if everything were built at the same time. But if additions were that simple, we’d have fewer ugly additions in the country. The truth is that blending the new with the old is a balancing act, and there are a lot of aspects to consider.

If you have any hope of blending new with old, you first need to understand the architectural roots, proper usage, and ideal proportions of each element. Then, you have to be willing to compare this idealized version with the often less-than-ideally designed trim of your house, and deal with the hard decisions about which architectural rules you’re willing to break in the name of honoring the original design. Of course, on top of all these aesthetic and proportional considerations are the pesky realities of structural needs and material transitions, which are really what the trim is covering in the first place.

I believe that the easiest way to make sure the overall aesthetics of any addition look right is to work from the outside in, by first deciding on the finishes and then thinking about how to hide the structure within those finishes. So that’s where I started with my porch design.

Learn the rules, but be ready to compromise

The good news is that there is no shortage of credible information on architectural details, and whether you’re following traditional details or working on a more contemporary style, the basic tenets still apply. Most elements of a building are rooted in structural necessity. Building materials have changed and advanced, but the purpose of those original elements is usually still sound.

Armed with information on these architectural details—in my case, the name, function, and order of each roof trim element—you then have to decide on the relative proportions of each piece. For instance, generally speaking, the amount that the cornice projects beyond the face of the frieze and architrave should be about the same as the diameter of the column that the entire entablature rests on. The frieze and architrave should each be about one-half or three-quarters as tall as the column is wide. But if you’re working with an existing house and tying into an existing trim package, you have to strike a balance between textbook and reality.

On my house, the exterior trim has somewhat exaggerated proportions, with a wide frieze/architrave and deep overhangs. Although the frieze is typically separated from the architrave below by a strip of molding known as a taenia, my house didn’t have this separating detail, so I decided to omit it from the porch trim as well.

I also decided to reduce the overhangs on the porch for a couple of reasons. First, I wanted the porch to look subordinate to the house, and one way to do that was to scale down some components. Reducing the overhang also allowed me to tie the porch roof trim into the sides of the boxed eaves rather than trying to build it in perfect alignment with their faces. Jogs and reveals are where a carpenter can hide the realities of trim work.

The house does have the traditional crown molding along the roof edges and bed molding under the beadboard-clad soffits, but whether because of personal preference or architectural ignorance, both profiles were installed upside down. I decided to replace these two pieces of trim, along with the fascia and soffit on the boxed eave overhang, eliminating the need for the new crown molding, bed molding, and beadboard to exactly match the old. A minor variation in a trim profile from one side of the house to the other would be inconspicuous, but even a slight variation stands out if you join the pieces together.

Work your way in

After deciding on these compromises and drawing the assembly in section view, I was able to determine how much room was left for the structural components, such as the rafters and beams.

Adding together the vertical height of the frieze and cornice gave me roughly 20 in. of space to work with—more than enough to conceal appropriately sized rafters and a carrying beam to meet my structural span requirements. I also found an opportunity to add a cool traditional detail. After figuring out the overhang, I realized I had more than enough room to hide the roof gutter within the entablature. This wasn’t something I had planned, and likely not something I would have thought to include if I were designing from the inside out.

Now when I stand back and look at my porch, I’m pleased with how the new structure blends right into the 91-year-old house it’s connected to. It looks like it belongs.