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  • Writer's pictureMaria Luisa Castellanos

Miami residential architects explain 3 things to know for planning your future home addition

Updated: Aug 23, 2023

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Everybody has hopes of improving his home once he buys it. This is one of the easiest ways to make money. Invest in your home while you live in it and then sell it and move to a better one or build an entirely new home.

But what are some of the things that catch people by surprise that may restrict them or make the addition an impossibility? As Miami residential architects, we can help you go through some of these issues.

Flood Zone

The first thing you need to check is whether your house in a flood zone according to FEMA. If you buy a house in a flood zone, you can only add to it or renovate it up to the value of half of the actual building or you must bring the house’s ground floor to one foot above the community’s base building elevation as determined by FEMA. For example, let’s say you buy a $750,000 property and the county says the building is worth $400,000 and the land is worth $350,000, then you would have a $200,000 total budget for the renovation. This may not be enough for an addition today. You can read more about this problem and what is a solution by reading my blog post at


The next thing you would need to check is what is the zoning for the property. What are the setbacks for your property? There is the front, sides, and rear setbacks. These are the distances you need to keep from the addition to the property lines. If you don’t have enough room left to meet these setbacks, you will not be allowed to build the addition.

Then, there is the maximum lot coverage or footprint. This is usually expressed as a percentage of the lot size. For example, if the lot is 50’ x 100’, that’s a 5,000 S.F. lot. If the allowable lot coverage is 50%, that would allow you to build 2,500 S.F. If your present house, for example, is 2,000 square feet, then you would be able to add 500 square feet.

Another issue is the maximum allowable square footage for the property. Let's take the same 5,000 square foot property and assume the maximum square footage allowed is 35%. And let's suppose you already have a 2,000 square foot house there. Since 2,000 is more that 1,750 square feet, you will not be able to add to the property. Some municipalities allow you to try to get a "variance", which is a way of getting around these requirements, but this may be difficult or impossible. You would have to speak to the zoning staff to see if there is a possibility for this.

Septic Tank

This is another critical problem. When you add an addition, you are adding square feet to the house and possibly an additional bathroom. This may be enough to require a larger septic tank and drainfield. The septic tank is not such a problem, but today, you may need not only a drainfield but a reserve drainfield. These two items take an immense amount of space in a yard. It looks like grass, but you need plenty of grass area for these two areas. I recommend that before you embark on a complete set of drawings with an architect and engineers, do the preliminary with the architect so you will know the footprint of the house with the addition, and then do the septic tank design. If you don’t do it this way, if the septic tank and drainfields do not fit, you could have a beautiful set of plans and not be able to build the addition.

Call me, Maria Luisa Castellanos, at 305-439-7898, and I can help you determine if your project is feasible.



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