How To Build Decking On A Slope The Right Way

Sloping ground presents a number of obstacles when it comes to installing a deck. Because you deal with uneven ground, you need to consider the severity of the land’s slope to ensure that your deck is level, flat and stable. Taking on a project like this can be a fun way to improve your outdoor space and upgrade your patio while also potentially increasing the value of your home.

New wooden deck during nice weather

Building one can be challenging, even more than building it on grass, but it’s simple once you know what measures to take. So, if you’re planning on building a deck on a slope, we’ve put up this simple guide to give you an idea of how to build your own and what to expect along the way. 

Make a plan

1. Know the decking building codes in your area

The size and shape of your deck will be determined by the size and shape of your home. In most circumstances, your deck will be required to carry a heavier load than your home’s flooring.

2. Check if you need any permits 

Before you start building your deck, check with your local government agency to see whether you’ll need a permit and if any inspections will be required. You may well need planning permission if you are going to build an elevated deck.

3. Know how deep the frost line is in your area

The frost line is the depth at which the earth freezes in the winter, as measured over a number of years. When creating a deck, some building rules require that the support posts be sunk to a depth below the frost line. 

Sinking the support posts to this depth, even if it isn’t required, will prevent the deck from sagging when the ground expands and swells as the water in it freezes.

Man maki plan and select materials for deck

4. Choose the size, design, and location of your deck

You might have a free-standing deck or one that is attached to the house. Although certain building rules allow for free-standing decks, most people find that having theirs attached to their home is more convenient. 

If you’re attaching your deck to the house, you’ll need to know where the rim joists and wall studs are so you can secure the ledger board to one of them. A ledger board is the support beam that connects the deck to the house.

The number of footings and posts you’ll need to support the joists and decking boards, as well as the size and distance between the boards, are all determined by the size of your deck. The distance between joists can be 30, 40, or 60 centimetres. However, the most typical is 60 cm.

5. Select the materials for your deck

You can build your deck out of a variety of hardwoods and composite decking materials. Boards are made of a variety of materials, including tropical hardwood Ipe and plastic, as well as more classic redwood, cedar, and pine. 

Pressure-treated or otherwise decay-resistant wood should be used for the decking frames, columns, and posts, as required by code.

Prepare the decking area

You’ll need to clean the area before you start assembling your deck. This includes removing the top layer of grass, vegetation, and dirt from the area where your new deck will be built. Make sure that you dig to a depth of at least 5 cm throughout the entire surface.

After that, you’ll need to mark the locations for your corner posts and dig the holes. This will pave the way as you later start to install decking posts and fasten them in place.

How to build decking on a slope step-by-step

Here is a list of the basic tools you will need for this DIY project:

  • Measuring tape
  • Twine 
  • Hammer
  • String level
  • Plumb bob
  • Spirit level
  • Posthole shovel
  • Mitre Saw (a circular saw, jigsaw, or even a manual crosscut saw will work)
  • Electric or cordless drill with assorted bits
  • Pencil or marking pen
  • Screwdriver (if you are using decking screws)
  • Wood or pipe clamps in various sizes
  • Carpenter’s square

The steps below will show you how to build a level deck on a slope safely and correctly:

Man putting wooden decking boards

1. Install deck posts and dig foundation holes

Pre-drill two holes, 30 cm in diameter and go deep enough to find solid soil, which can be 30 or 60 cm down.

The perforations will aid in the support of one of the deck’s sides. Next, insert a deck post into each hole and measure the posts from the bottom to the deck’s height, adding 30 cm to each post’s end. Once you’ve determined the final height of the deck, you’ll chop off the excess length.

2. Fill the holes with concrete

Concrete should be poured into the holes and allowed to dry completely. When the concrete begins to dry, use a water bubble level to determine whether the posts are level. 

Place a string on each post and extend it to the desired location for the other side of the deck. For the time being, leave the strings on the posts and make a mark in the ground where the support posts will be placed.

3. Work on the deck’s second side

At the bottom of the slope, you’ll need to dig two more support holes for the other side of the deck. Fill the holes with two long deck post beams and measure them with a thread to ensure they’re long enough to hold your deck. You’ll repeat the process on the other side and use concrete or paving slabs to fill the holes you just made. 

Make a guide for your floor beams by tying the string to the new posts at the height you want the deck to be. Hold a level up to the string to ensure that it is stable and straight. Make a mark on the posts where you want the deck beams to be secured. 

Use 7 cm bolts or nails to secure the posts and deck beams, and use the mark you made as a guide. Make sure to use beams that are the right length for the type of wood you’re going to use to frame both sides.

4. Get the floor beams in place

Attach the floor beams to the deck beams with 7 cm nails or metal bracing. You may be required to adhere to local building rules that govern the proper spacing of decking floor beams. After that, you’ll use screws to secure the boards across the beams.

5. Add a railing

For safety purposes, many decks that aren’t at ground level may require a railing. Check your local building codes first to see what the railing spacing, baluster width, and height requirements are. 

You can buy a prefabricated railing system at several home improvement stores for a quick solution. It’s also simple enough to build using a 60-by-60-cm piece of timber and a basic design.

Make sure your balusters are cut to the right height. A common deck railing height is from 0.9 metres to 1.1 metres. After that, trim the top rail pieces to be about 0.6 metres in size. 

Lag screws will be used to secure all of the balusters to the decking‘s outer edge. Make sure that the expansion gap between each one is no more than 22 cm. As you go along, make sure they are plumb by using a spirit level. Use deck screws to secure the support posts and pickets to the top rail.

6. Add a wood finish

Finally, you’ll want to finish the deck with paint or an external wood stain. Before you start staining or painting, locate all rough areas and sand them down to prevent splinters from developing. 

Men adding wood finish in deck

Before applying another layer of paint or stain, make sure each coat has had enough time to dry completely. Apply polyurethane after the stain or paint has dried to protect the finish even more.

Allow for drying time between coats and lightly sand the surface. If the area is particularly large, consider using professional landscaping equipment for this woodworking project to ensure a smooth surface and successful completion.

Maintenance and safety tips

  1. Apply a decking stain after the decking is finished to further protect the wood.
  2. Treated wood offcuts should never be burned, but should be disposed of properly. Your neighbourhood recycle centre should be able to help.
  3. You should also keep in mind that joists are heavy, so move them with caution or ask for help.
  4. To protect the wood from wet and algae growth, apply a special treatment by using a solvent-based wood preserver.
  5. The frequency with which you should treat the decking will be determined by its location.
  6. Brush away any debris or leaves from the deck on a daily basis to keep it clean.
  7. Secure the wood firmly and use caution when sawing or drilling.
  8. Wear a dust mask, safety goggles, and protective gloves when drilling.
  9. When operating a jigsaw or circular saw, make sure to have a dust mask, ear protection, and safety eyewear.
  10. When sanding any cut ends of wood, wear a dust mask too.
  11. When using a wood preserver, always follow the manufacturer’s instructions on drying and safety.

House with deck

Voila! you won’t need any help installing decking on a slope if you follow the steps above. You’ll be able to do this project quickly if you plan ahead with the right steps and gather all the resources you’ll need. The end results? A beautiful and functional deck that will take your home to the next level! And if you’re ready for your next amazing project, then here you can learn how to build a roof like a true pro.

Scroll to Top
Send this to a friend