An addition to a commercial building changes the exterior structure, the footprint, or the height of the structure. Depending on the size and location a lot of grading permits may be required. 

A development, building, and all sub-trades (electrical, plumbing, and gas) permits are required to construct an addition onto an existing commercial building.

A project that would not involve any work on the outside of a building or to the site, and wouldn’t change the legal use of any part of the space, is generally one of the simplest types of permits that we issue. An example of this type of project is where an existing office or retail space would be remodeled for a new office or retail tenant, or where the existing tenant wants to make some changes to the layout. 

If this will be a new location for you, and even if you will be using the building for the same use as did the previous tenant, we recommend that you check the building permit records to make sure that the user has actually been permitted and that a change of use permit will NOT be required. It is not uncommon to find buildings that, for many years, have been used in a way that has never been approved through the permit process. Legalizing a change of use can be a lot more complicated and expensive than remodeling an existing legal use. You can avoid surprises by doing the research ahead of time. 


Even with relatively simple interior remodeling projects, there are some potential complications to be aware of — most of which have to do with improvements that could be triggered based on the value of the work.

The Challenges of Addition to a Commercial Building

We receive a lot of inquiries from building owners about doing additions. Generally, they are interested in expanding out the back or along the side, but once in a while, we get asked to help expand by going upward. This could be a residential pop-top or a commercial project adding a new story.

Adding onto the top of an existing building yields a number of unique challenges for the building disciplines.

In the architecture realm, you need to get people up to the new upper level so the floor plan needs to accommodate that on the existing level. Generally speaking, your existing roof will not be your new floor deck, so the roof and anything contained in the roof will have to come off, meaning a lot of relocation and patching where items are located in space above the ceiling.

In a multifamily or commercial project, you will also have to look at fire ratings, building areas, sprinkler requirements, and all the other items that come with additions to these project types.

Structurally, the building needs to be evaluated to see if the existing bearing walls, columns, beams, and footings can support the additional load. Typically the structure will need some upgrades, the question is how much it adds. If the new story does not stack nicely it becomes complex fast.

You’ll find that a lot of your plumbing and mechanical systems are located on the roof. That means that those items have to be rerouted and relocated. Sometimes they may also need to be upgraded for the longer runs.

Finally, keep in mind that in any addition or remodel with a large investment, you’ll likely trigger a need to upgrade the rest of the building to meet codes which can be a serious investment.

In any scenario where you want to add to a building, you’ll need the services of an architect to help you navigate the process with these challenges and others that are unique to your building.

Suncoast Permits is here to guide you through every step of your commercial permit processing, contact us today