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How to build a carport on sloping ground?

Hi again, Bunnings community!

We're in the process of replacing our old carport that's situated on the side of our house, which is on sloping ground. The previous carport was a split-level design, but unfortunately, it was too narrow for any practical use of parking cars, so we had no choice but to tear it down.

We're now planning to have a new carport installed, and I'm at a bit of a crossroads about how to approach the slope of the land. I'm pondering whether to:

1. Make the entire carport level, which might involve modifying the slope by either cutting down the higher end or filling the lower end to achieve a flat surface.

2. Not worry about leveling and simply construct the carport to follow the natural slope of the ground.

3. Opt for a split-level design similar to the previous one but hopefully more functional in terms of space.

My biggest concern with leveling is the potential need for retaining walls. If I decide to level the ground, should I attempt to balance the cut and fill across the slope to minimize the height difference and possibly the need for extensive retaining walls?

I would greatly appreciate any advice, especially from those of you who have tackled similar projects or have expertise in landscaping or construction. What are the potential pros and cons of each option? Are there any specific considerations I should take into account regarding drainage or structural integrity?

Thank you in advance for your insights!

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EricL

Hello @Sebastian90

Thanks for sharing your question about building a carport. Allow me to try and answer some of your questions.

Whether you cut into your driveway slope or add on to it, I suggest engaging the services of an engineer. They will draw up the plans for the retaining wall and your car port which will be done to code. This will allow you to submit your plans to the council with confidence that it's in line with their rules and regulations.

Between the two options, I would recommend the top up option, as it won't interfere with your house foundations.
Leaving the slope as is, is the economical approach as you won't have to do a lot of earthworks and concreting. You'll still need an engineer to draw up the plans, but you won't need to install retaining walls anymore. This also saves you from having to worry about putting in new drainage.
I propose going with a single roof design as it makes planning and construction a lot simpler. To compensate for the sloped driveway, I suggest making your roof bigger or longer so that it covers your cars even if they are on a slope.

I agree with your assessment of putting in retaining walls. Digging into the slope means that the retaining walls will need to be very strong as it is very close to the foundation of the house. Unfortunately, there is no escape from the retaining walls whether you decide to dig or top up.

Let me call on our experienced members @Dave-1, @homeinmelbourne and @TedBear for their recommendations.

If you have any other questions we can help with, please let us know.

Eric

Dave-1

Good Evening @Sebastian90

Yeah, thats a bit of a slope to handle... Tho sounds like you have given it some solid thought,

I Like the idea of using a bit of option 1 and a bit of option 2 that you have mentioned.

I have build a few retaining walls using Gabion cages and they have worked very nicely and have not shifted in 3-4 years (The free standing ones have been standing for a decade!) Large gabion retaining wall build is the largest wall that I have built but if you troll through my bookmarkes athere are a bunch of others. The one that is retaining a sloping path with a timber top might be a good idea for what you describe. Gabion wall bench seats

If you cut into the slope a little and then install a gabion wall it would give you that carport space. The Gabion wall allows drainage through it without a worry. The only thing you really need to do is to make sure the footprint of the wall is compacted soil or as little disturbed as possible. That large wall had undisturbed soil/compacted and also went over where I had put a new stormwater pipe in. By all rights I should have compacted it more but its only dropped an inch ish in the 2-3years since I have put it in. The wall has not rolled forward at all 🙂

If you dont mind a sloped base for the rest of the carport then you could have a high roof with a large span. As @EricL suggested I would also get an enginneer for the carport, just because its going to be oversized and would really not want it to lift in any wind.

I dont think id rely on a gabion wall on the low side to support the weight of a car/truck/ Yes they are solid but an extra Ton or two on top.. "Shrug" I love gabions but I am not that game 🙂

I would probarly factor some sort of drainage to take care of the large surface area just so you dont end up with slippery spots on the concrete.

Dave

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