How to build a garden fence on a slope


I’ve been waiting for the right jobs to come along before writing an article explaining how to build a garden fence on a steep hill or slope and that job has finally came where I can not only explain how to do this, but I can also show you pictures of my work. Essentially there are 2 ways to build a fence on a steep slope or hill, one with a feather edge fence (also known as closeboard fencing) and one with standard fencing panels. Luckily, this job had both styles of fencing at different ends of the garden!

When we think of a garden fence, we usually imagine them being nice and level across the entire length of the garden but in reality it’s rare to find any garden perfectly level. A gradual climb isn’t cause for concern but when it comes to building a fence on a particularly steep slope or hill then more planning may be required.

How to plan your new garden fence on a slope

On this slope the total depth between each gravel board was 10 inches allowing us to use 12 inch gravel boards and standard fence panels

With any panel fence it’s always good practice to use gravel boards to keep the fence panel off the ground and unless your garden is perfectly level then this is especially important. With no gravel boards being used your fence panel will be exposed to the elements and begin to rot from the bottom up over a period of time. With any sloped garden regardless of how gradual it is, one side of your fence panel will be buried under the ground and therefore rot quicker than if it were simply resting on top of a level ground or raised from the ground altogether when using gravel boards. This is why concrete posts and gravel boards will always outlast timber ones since they won’t rot over time.

For this reason above, if you can get away with using fence panels on a slope then you are going to need to use concrete gravel boards. Essentially there are 2 options available, 6 inch and 12 inch concrete gravel boards. The way to work out which ones are needed is by measuring the depth from one end of a fence panel to the next. Most fence panels are 6 feet wide so using this width as our example I would usually find the steepest part of the hill or slope and starting from the lower point, dig a level trench 6 feet wide. The closer you reach your 6 feet goal, the deeper the trench will be. When you get there, simply measure the height from the bottom of the trench to the height of the ground. The height of the ground will usually be where the next concrete gravel board will begin. If the height is 6 inches or less then you can use the smaller 6 inch gravel boards. A depth of 12 inches or less then you will need to use the 12 inch gravel boards. For depths of up to 450mm you can use a 6 inch and 12 inch gravel board together but any slope steeper than that then I would recommend changing from standard fence panels to building a featheredge or closeboard fence. Remember that you will want your fence posts sitting at least 2 feet into the ground so 8 foot posts are best for a fence height of 6 feet but any fence taller will need a 9 foot fence post. The image above shows a 6×6 feet fence panel accompanied by a 1 foot gravel board, totalling 7 feet in height. This meant that we used 9 feet concrete posts.

This slope was just too steep to use standard fence panels. Instead we built a featheredge fence running up the hill.

The reason that we need to build a featheredge or closeboard fence on a particularly steep slope is because you can simply run your gravel boards up the hill and your slats will naturally follow suit. There is no need to dig a level trench. When using fence panels you are limited to the depth of the hill due to the panels needing to be level. If the slope is too steep then you will end up having one end of the fence panel underground.

When building a featheredge fence you can use concrete posts and gravel boards, however the gravel boards need to be bolted to the posts with brackets as they aren’t slotted like the panelled posts. For this reason, it would be very difficult to cut the concrete gravel boards at the angle needed and still be able to bolt them to the posts. Even if you did pull it off, it wouldn’t look very good. I would recommend building a featheredge fence out of timber fence posts and gravel boards when running the fence up a hill.

How to build a panel fence on a slope

As this guide is aimed specifically at building a panel fence on a slope I’m going to try and keep it simple. For a more in-depth guide on how to install fence panels and posts then just follow the link.

  1. Before building or even ordering your new garden fence check that the slope isn’t too steep to handle fence panels. The picture above is pretty close to the limit. As you can see, the gravel boards are all level but are also all above ground. There is a 10 inch drop between fence posts and therefore these 12 inch gravel boards just about managed it.
  2. Start by installing your first fence post. All you need to do at this point is dig a hole at a depth of 2 feet using your post hole diggers and use postfix to set in place.
  3. If your new garden fence is going to be in a straight line then I would recommend installing your last fence post so that you have a post at each end of your fence line.
  4. Now it’s time to tie your builder’s string from post to post as this will give you your straight line.
  5. Measure 6 feet from your first fence post (providing you are using 6 feet fence panels) and dig your next post hole. You can temporarily lay a gravel board between the post and hole to make sure you have dug in the correct place.
  6. Dig a level trench from your fixed post to your new post hole. Your trench will start at the lower ground level and end up underground as you reach your post hole.
  7. When you are happy that your trench is level, it’s time to lay your gravel board in the trench – Use a spirit level to make sure it’s level.
  8. With your gravel board now in place, rest your fence panel on top of the gravel board and in to the slotted fence post.
  9. Once finished, all you need to do is slide your fence post into the hole and making sure the post is level whilst the gravel board and fence panel are in the slotted in place. Make sure that the height of the new fence post measures 6 feet from the new ground height (if your installing a 6 feet tall fence) as the next gravel board will be starting at the new height.
  10. Finally, make sure that your fence post is in line with your string line before setting with postfix and carry on with the next fence post until you finish building your new fence. If you find any roots in your way then you can read my article titled ‘how to dig post holes through tree roots‘.

How to build a featheredge fence on a slope

With a closeboard fence you start by ‘carcasing’ the fence before nailing the slats on.

For those slopes or hills that are particularly steep, you are going to want to build a featheredge or closeboard fence running up the hill with wooden posts and gravel boards. No matter how steep the hill is, you can always find a way by building the fence yourself. Unlike fence panels that need to sit level, closeboard fencing allow you to build the fence at the same angle as the slope.

Here you can see the featheredged fence now has gravel boards installed and we have nearly finished nailing the slats onto the arris rails.

You can read my full guide on how to build a featheredge fence here but below is a quick guide to building a featheredge fence on a steep slope or hill.

  1. Start by digging your first post hole with your post hole diggers and installing your first fence post. Make sure that the fence post is 6 feet above ground before levelling and setting with postfix (unless the height of your fence will be different ofcourse). As the gravel board will be installed at an angle, you may need to install your first post an inch or 2 higher depending on the depth of your slope to avoid the gravel board partially being underground although its not completely necessary.
  2. Once your first post is installed, I would recommend installing your last fence post using the same method above so that you can tie your builder’s string from post to post and getting your straight line.
  3. Using your arris rail, mark where your next fence post hole needs to be dug. It’s best to use ended arris rails and fence posts as they work much better going up steep hills when slotting into fence posts compared to using non-ended arris rails and v-notched fence posts.
  4. When you are happy with the depth of your post hole, loosely rest your fence post within and check that the height of the fence post is correct from the new ground level as you go up hill. It’s OK if it’s too low as you can always raise it later on.
  5. With the help of another person and starting with the lowest arris and working your way up, slot the arris rails into both posts. The loose post will need to be pulled back whilst you slot the arris rails into place.
  6. With your arris rails securely attached between each fence post, make sure that your new fence post is level and and use postfix to secure into place. Before adding water to your postcrete you can carefully raise the fence post whilst keeping it level if it’s sitting too low. Continue this process until you finish your fence line.
  7. Now that your featheredge fence is ‘carcassed’ it’s time to install your gravel boards. Since your new garden fence is being installing according to the depth of the slope, the cuts will need to be at an angle. The way I do this is by first nailing 1 slat onto each end of the posts. Now you can temporarily screw a gravel board to the outside of the fence posts, making sure that it is screwed on at the same height as the bottom of the slats. If your ground is too high to achieve this then dig a shallow trench until able. Once done, simply draw a line where whe posts meet the inside of the gravel board. This will be where your cuts need to be made.
  8. Using some batton, cut some 6-8 inch lengths and nail them just behind the slats, making sure they are level. 2 nails or screws will be enough. Now you will have something to screw your gravel boards on to.
  9. Finally it’s time for the easy bit! All you need to do now is nail your slats onto the arris rails. Depending on the width of your slats, start by cutting a piece of timber to a length of 25mm less than the width of your slats. For example, if I’m using 125mm wide slats then I will cut a piece of timber to 100mn (an off-cut from the gravel board will do) and mark a line 100mm apart up the arris rail. This will ensure that your slats are an equal distance apart. Using a long spirit level you can now mark a level line from the top arris rail to the bottom before lining up your slats and nailing them into place to finish your new featheredge or closeboard fence.

My thoughts on building a garden fence on a slope

Where there’s a will there’s a way. No matter the depth of your slope or hill you can be certain that you can build a fence on it! Just look at the closeboard fence above – The customer had 2 companies say that it couldn’t be done, yet 2 if us had built it in 2 days. I would always recommend using concrete fence posts and gravel boards where possible as they will always outlast timber options but if the slope is too steep then timber will be just fine. If in 10 years the bottoms of the posts begin to rot then you can always install concrete spurs. Wooden gravel boards are always going to be easy to replace if needed and since the slats are elevated from the ground, these should outlast the posts and gravel boards anyway. Just be sure to plan around your slope and choose the best style of fencing for your needs. If you get stuck and need help then please comment below as I will always be happy to help! I’ll be adding more pictures soon to better explain how to install build a fence on a slope but in the mean time, I’ve tried to explain it as best I can!

Below are some product links for the tools needed to build a new fence on a slope

For my recommended tools needed to build your new garden fence on a hill please visit my Amazon storefront here. I’ve also included some product links below. As an Amazon affiliate partner, I receive a commission for any purchases made using the below links.

Your not going to get very far without post hole diggers! An absolute must have tool for digging your post holes.

With your post hole dug and your fence post in place, you’ll need some postcrete to set it in place! Just add water!

My most forgotten piece of equipment is builder’s string! And trust me, you will need it for any straight fence.

I can’t believe I nearly forgot to add a set of spirit levels! Builder’s string will give you a straight fence line but it won’t give you level fence posts!

Ofcourse you are going to need more than what I’ve listed above so why not head over to my Amazon storefront of recommended products for building a new garden fence on a slope just to make sure your not forgetting anything!

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