Welcome to our four-part patio door series, where we’ll break down everything you need to know about patio doors, from selection to installation. In this installment, we discuss all the factors to consider before beginning your next patio project. 

If you’re considering replacing your patio door, the first thing to do is talk to an expert about choosing the right one. Once you’ve picked your door, you’ll need to consider all the project variables—whether you’re planning on completing the project yourself or hiring a professional. Before you begin, take the time to address the items below to increase your chances of having a smooth removal and installation process.

Job site access

A lot of logistics go into a door replacement project, so it’s important to make sure it’s easy to access the job site. Considerations include delivery access, material storage, and transportation of tools and materials to the work area.

Continuous design

The style of your door should blend seamlessly into the overall design of your home. Look to the profiles of your existing windows, doors, and millwork for inspiration. If your home has a wood interior, you may want to identify the type of wood and choose a door of the same composition. Overall, it’s about blending the new door with your existing home.

Exterior siding and trim

To achieve a seamless look, you’ll need to identify how your existing siding and trim will interface with your new door. You might need to make modifications, so it’s important to identify the type and size of any exterior trim. Knowing the size and ideal locations for both interior and exterior trim will aid in choosing the size of your new door.

In many homes, trim is absent, and the siding butts up to the door. This covers the nailing flange, which makes removing the existing door difficult. If this is the case, one option is to cut out the siding just enough to remove the existing door. When the new door is installed, the siding can be cut farther to accommodate the installation of exterior trim.

What to Consider Before Installing a New Patio Door

Squaring issues

Every home is built differently—and many houses settle over time—so you’ll need to use a level to see if the door is out of plumb and by how much. A little is usually not an issue, as framing typically allows at least half an inch of extra room to aid proper installation. It’s generally best to set the door plumb and square, but sometimes a door does need to be set out of plumb to match the existing lines of the home. In that case, it’s best to work with an experienced installer.

Weather-resistant barrier integration

Most homes have some sort of weather-resistant barrier (WRB), whether it’s a felt or tar paper product, a more modern housewrap, or a rainscreen system. In all cases, it’s important to use best building practices to tie in the existing WRB as much as possible. The key is to leave the existing weather barrier alone when you remove the exterior trim, as it will help keep your wall cavity dry. In high weather-exposure scenarios, you might consider removing more siding and adding additional WRB to make sure your home is adequately protected. 

Sill pan use

All door manufacturers recommend using sill pans with each door installation. A sill pan will help collect moisture and channel it to the exterior, which further protects your home. Sill pans range from plastic, preformed pieces that can be glued together to custom-made, one-piece stainless steel. Any type of sill pan is better than none.

Floor to door transition

It’s important to figure out how your floors will interface with the sill of your new door. First, identify what kind of floors you have. Then, look at how the flooring interfaces with the existing door. If there’s a transition strip of trim, you might need to remove it to determine how thick your flooring is. Oftentimes, the thickness is around 3/4”. However, watch out for multiple layers of flooring—it’s fairly common to install a new floor over an existing one. Take these measurements into account so the sill of your new door doesn’t end up lower than the finished floor. 

After installation, a trim piece can be used to hide the gap at the transition between the sill and flooring. This piece can be made to match the flooring or painted to match the existing trim.  

Interior trim

When I replace doors, I carefully remove the interior trim so it can be reused. Existing trim is already cut and painted or stained, which saves the time and expense of reinstallation. If your trim is custom made, I would highly recommend saving it for a reinstall. It can be expensive to mill and match stains and finishes. But if your door needs painting or staining, it may be an advantage to replace the trim since painting or staining has to be done anyway.

Replacing doors is a complicated process, but thankfully there are sales professionals who know these products well. Whether you’re doing your own installation or hiring a licensed professional, taking the time to properly evaluate the above items will help lead to a smooth installation of your new patio doors. For more information about patio doors, check out the first installment of our patio door series, this guide on how to know when to replace or repair your patio door, and this weatherproofing video. Be sure to stay tuned for the final two segments in our patio door series.