Alan’s Metal Carport Buyer's Guide

You have several options for your carport foundation:

• Existing driveway
• Ground
• Gravel pad
• Concrete slab
• Asphalt

In this chapter I’ll explain the pros and cons of each option. I’ll also explain the requirements for each type of foundation.

Existing Driveway

There are two ways we can install your carport over an existing driveway:

If your carport is wider than your driveway, we can attach the frame of your carport to the ground beside your driveway with the appropriate ground anchors.

If your concrete driveway is at least one foot wider and one foot longer than your carport, we can attach the carport frame to your driveway with concrete anchor bolts. Just make sure the driveway is level. The carport can’t be installed correctly if any corner of the carport site is more than three inches higher than any other corner.

Ground

Your carport can be installed on the ground if your local building department allows it. The installers will anchor the carport to the ground with the appropriate ground anchors.

A dirt foundation is suitable for storing farm and garden equipment. If you want to keep your vehicles clean, a gravel foundation is better.

Gravel Pad

A gravel pad is the most popular and cost-effective base for a metal carport.

How big should a gravel carport pad be?

I recommend making the gravel pad at least two feet wider and two feet longer than the carport. This way you’ll have a little room to walk around the carport. A slightly wider pad will ensure that rainwater that runs off your carport will fall on gravel. Otherwise, muddy water might splash into your carport.

How deep should gravel be for a carport?

I recommend that you put down four to six inches of gravel. If you have more than six inches of gravel, please call me to discuss this as we may need to use longer anchors or may not be able to install the carport.

What kind of gravel should I use for a parking pad?

The best gravel for a carport is 3/4” stones mixed with smaller stones. The smaller stones help the gravel compact into a solid surface that is almost like concrete.

This type of gravel is called by many different names, like:

• 3/4” Crusher Run
• 3/4” Crushed Stone
• 57 Crusher and Run
• #57 Aggregate
• ABC Stone

How do I prepare a gravel carport pad?

• Remove the topsoil
• Level the site as much as possible
• Put down woven geotextile fabric (optional)
• Put down at least four inches of crusher run
• Use a compactor or a tamper to compact the gravel
• Verify that the gravel is level

How can I prevent water from pooling under my gravel pad?

The ground around your carport should slope slightly away from your carport so that water will not pool under your carport. Ideally, the ground 10 feet away from your carport will be at least six inches lower than your carport area.

If you have a problem with mud in your driveway or your carport area, put down woven geotextile fabric before you put down gravel. The fabric will prevent the gravel from sinking into and mixing with the mud.

How much does a gravel carport pad cost?

The gravel for a 22’ x 22’ gravel pad will probably cost between $250 and $500, including delivery. The cost of hiring someone to excavate the site and complete the work will depend on local labor rates.

Do a quick search for ”gravel for sale near me,” and take a moment to call and get a quote for your gravel. If you need excavation, call one or two excavating contractors to schedule a time they can look at your site and provide a quote.

Concrete Slab

A concrete slab is the best foundation for a carport, but if you have a slab installed by a professional, it will probably cost more than your carport!

You can save a lot of money by pouring the slab yourself. In my Garage Buyer’s Guide I explain how to price and plan a concrete foundation and how to cure a concrete slab. I encourage you to read those chapters if you are considering a concrete foundation for your carport.

Asphalt

Asphalt is a cheaper alternative to concrete, but it isn’t the best choice for most people.

Asphalt Pros

• Up to 50 percent cheaper than concrete
• Works well in cold areas where the ground freezes and salt is used to melt ice and snow
• Grease stains blend in

Asphalt Cons

• Soft—deforms under heavy loads and softens in extreme heat
• Higher maintenance—needs to be re-sealed every few years
• Doesn’t last as long as concrete
• Doesn’t look as nice as concrete

If you live in a cold area with lots of snow and you frequently salt your driveway, asphalt may be a good choice. However, gravel or concrete will make a better base for most carports.

If you’ve read this far, well done! It’s a lot of information, but it’s important to understand because the foundation of your carport is crucial.