Phew! I was a little worried about how my choice to replace the rotten wood arch with foam would go over but y’all are an understanding bunch. I honestly think it’s the best choice for this project and I had a few questions about it on the past post.

First off, I am not an expert on this subject but I’ll gladly share what I’ve learned. At the very least, it might serve as a starting point for your own research.

This is the second time I will be using foam on the house. The first time was in my 2nd floor bathroom, so we’ll start there.

Both the crown moulding and the center medallion in the bathroom are foam. In comparison, the window casings are original & solid wood.

Why foam? Well, for a couple reasons.

Most homes don’t have crown moulding like mine. I’m spoiled/lucky/blessed/whatever you want to call it. It’s a historic home. While they come with a lot of work & problems, they also come with awesome details like bigass crown moulding.

I wanted giant chunky mouldings but didn’t want to layer multiple pieces to achieve the look. (Like this -)

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Urethane moulding gave me the size I wanted at a price & weight I could manage. Because urethane is so lightweight, it was easier for me to hold up & install by myself. They’re also water-resistant but install just like wood. I ended up using this crown and this medallion.

The 2nd floor bath is one of only 3 rooms (the other bathroom & my closet) that don’t have crown moulding. It was also the only room on the 2nd floor without it, so it looked kind of odd & out of place. The room felt more like a part of the house once the crown was installed.

It’s relatively simple to install, as it goes in just like wood crown (except lighter). I used a combination of adhesive & brad nails (cordless Paslode finish nailer FOR THE WIN!), although you could screw it, if you wanted. I did have to borrow a bigger miter saw from a friend though. Because the crown was so wide (about 10″), I needed a compound miter saw with a sliding arm.

(That’s me cutting the baseboards but the crown was about as wide. The saw was just barely big enough to cut both.)

After using foam in the bathroom, it was actually my mother who suggested using foam to replace the rotten wood arch out front. It was also my mother who took the above photo of the gawker. I don’t have a driveway or a garage, so the street becomes my workshop and people get curious. You’re welcome, Newark.

For the arch, I looked at architectural foam. What’s the difference between urethane & architectural foam? Well – (& here’s where you remember I am NOT an expert on this topic. yet.) – a few things, from what I can tell comparing the two.

Neither will rot, split, or crack. Both are impervious to termites. Both are paintable. Both install just like wood would or with simply adhesive. Both are purely decorative, as neither are load bearing.

The differences are in how each is made. The urethane foam seems to be made of a finer grit foam, whereas the architectural foam reminds me more of a styrofoam cup. When cut, the urethane creates almost a fine, sawdust-like dust. The urethane one comes factory primed and the website says it’s ok for interior & exterior use.

Looking at a cross-section of it, you can see the coating is really thin. I wonder how it would actually hold up to exterior elements (branch or hail whacking against it, for example). Maybe in an overhang, where they’d be protected a little more, it would be fine.

The core of architectural foam is made out of expanded polystryrene (EPS) in a 1lb density. Sort of the same stuff as a high quality styrofoam cup. The shape is cut and then the whole thing is coated in a 2-step process. First they coat it with a thin layer of cement (the dark gray layer). Then it’s coated with your finishing product – either a stucco or paintable skimcoat – depending on what you want. The paintable skimcoat is shown below. While not load bearing, this shell seems harder & more durable to me.

Also, most places that do this sort of thing do lots of custom stuff. The urethane foams at Architectural Depot (there are lots of other places to buy them too) were all stock. While this arch will cost more than what I spent on my bathroom, it is completely custom and less than I would have spent recreating it in wood.

For my arch, I went with EPS from Trim Factory in Pilesgrove, NJ. We can chat about them more later but so far so good. They were one of the few companies who actually responded to my inquiries (my job is pretty small) and Peggy has been super responsive.

These giant EPS foam blocks get cut down with computer-driven precision to whatever your specifications are.

The scalloped pieces on the floor are slated to be installed on the walls of a curved room in some mansion. Fancy stuff.

Architectural foam comes in stock pieces, too. Here are a bunch of pieces that have their cement coat. The final coat is done after their ordered.

I don’t think one is inherently better than the other; it just depends on you job. The urethane foam worked great in my bathroom. Lets hope the architectural EPS foam works as well as I expect it to out front.