In this post, I’m going to show you how to build a DIY wooden decking area in your garden.  I’ll show detailed step-by-step guides on how I did this for both a raised floating platform and also a platform that sits on a solid base.

Below are two decking ideas for your garden, each including a canopy so they can be used all year round. You can build them on uneven ground, slopes or even hard surfaces. So if you are looking to save money on your decking build this post should hopefully provide some answers for you.

Although there are many companies that offer decking installation in London and the rest of the UK, completing this job yourself will be far more enjoyable and rewarding. Read on to learn how to build the perfect outdoor living space. Here are the two decking options I built.

How much does it cost to build a deck?

Each decking area was achieved for under £500, were built to last and provide an aesthetic seating area all year round.  You may also consider a composite decking board for this project but be prepared to spend extra for the longer-lasting materials. Composite decking is just as easy to work with as wood, comes in a vast variety of colours and will last a lifetime.

We managed to save a load of money on these two projects by doing it ourselves, using partially reclaimed materials, shopping around and using a cash back site like Topcashback.

Planning Permission

Before you get started you’ll need to ensure your decking area fits within the permitted building regulations and doesn’t require planning permission.  If you’re just going for a deck without the veranda, canopy or cover then it’s very straightforward:

1. Raised platforms must not exceed 300mm (30cm)
2. The total area of ground covered by the veranda must not exceed 50% of the land around the original house.
3. If joining to an existing building it must not be wider than the building

If you are planning on adding the veranda, canopy or covered section then you must also stay within these guidelines:

1. A maximum depth for a single storey building must not exceed 3000mm for an attached building and 4000mm for a detached building.
2. The maximum height must not exceed 4000mm.
3. The maximum height of the eaves within 2000mm of a boundary shall not be greater than 3000mm.
4. No extension in front of the main elevation or side elevation fronting  a public highway.

It’s always worth checking the UK Planning Portal for guidance and advise when considering outdoor structures of any kind.

Tools required

To get the job done quickly you’ll need to consider purchasing the following tools if you don’t already have them.  Whilst they aren’t all essential, they will make the whole process quicker and easier and will ensure a decent finish.  I’ve included some links to some of my favourite brands should you want any recommendations. (Remember to use a cash back site before making any purchases, You’ll be amazed how quickly it all adds up.  I’ve accumulated over £400 in under 2 years)

1. Tape measure – 8m tape measure
2. Pencil
3. Large spirit level – The bigger the better
4. Drill Driver – Dewalt drill
5. Impact driver – Dewalt drill and impact driver set
6. Mitre saw – anything that can chop more than 120mm
7. Hand saw – Panel saw
8. Shovel – Or spade
9. Bucket
10. Trowel – Normal garden trowel for digging
11. Workbench – Workmate

Materials

As I’m going to be talking through two different builds here I will include a materials list at the end of each.  You will however need to work out exactly what you require before you get started.

Save money

Saving money on tools and materials. If like me you like to save as much money as possible on your DIY projects then it’s worth signing up for a cashback site like Top Cashback. My wife and I have saved over £2700 in a couple of years on all our day to day spending! That’s a nice little holiday abroad for simply clicking on a cashback link.

Here’s a screenshot of my earnings to date. My wife has another £1800.

How to build decking on a solid surface

Skip to raised decking guide

So here we go.  This is how I build my decking area over an existing patio.  I actually pulled up the existing slabs and used the concrete underneath as the level surface to build on.  It was a little uneven in places but this was easily sorted with a hammer and chisel. This post will only cover the decking section of this build. Click here to see the veranda (canopy) step-by-step guide.

Step 1. Ground preparation

If like me you are building over the top of an existing patio you have the choice as to whether you want to remove the existing slabs or leave them in place.  This will depend on any height restrictions you may have, for example, the door frame height might prevent you from going any higher or lower.  You might also want to consider the height of the decking and how it joins onto the rest of the garden.  We are going to be installing porcelain tiles onto the end of our decking and wanted them to be level with the decking so I decided to remove the slabs underneath to ensure a flush fit with the tiles.

Step 2. Decking layout

Start laying out your support beams (joists) to form the total area of the decking.  At this point you will need to decide which way your decking boards will be facing.  Mine are all facing away from the house but you may want them parallel to the back of the house.  Either way you go you will need to make sure your spacing is correct.  Use the following chart to ensure you have suitable spacing between each joist.

Decking board size (mm)	Joist centre point span (mm) for C16 grade timber
20.5 x 95	300
20 x 138	400
27 x 144	500
33 x 120	600

I selected a thinner than normal joist due to the fact that the frame was being built on a solid surface.  I used a 3×2 CLS timber joists which measure 47mm x 38mm and 2.4m long.

Step 3. Cutting the supporting frame

This is where things became a little more tricky.  Starting at one end, each joist beam was cut to size and joined using a 80mm wood screw. Follow the image below for lining up each section.  For the joins that I could’t reach due to obstructions I used a Kreg Jig to create pocket holes.  This allowed me to screw in from the opposite side of the beam.

Step 4. Weed protection

As you can see above I’ve also added the weed protection now that all the pieces of the support frame have been joined.  This probably wasn’t absolutely necessary due to there being a solid concrete base but for peace of mind I added it anyway. I also used some flashing tape along the front and side beams to protect the wood from sitting in water. This tape costs about £9.00 for 10m.

Step 5.  Checking stability

Once all the beams had been joined I tested the whole frame to ensure it was even and secure.  The last thing you want is a creaky wobbly deck.  Whilst walking along each beam I looked to see if there was any movement throughout the frame, which there was.  To ensure a good solid frame I used right angled brackets to secure the frame to the floor.  I drilled holes into the concrete using a masonry bit, inserted a plastic plug and strong screw for a good solid fix.  I did this in about 8 different locations and then checked the frame again by walking across all sections.  Once all movement had been resolved it was onto the next step.

Step 6. Adding the decking boards

Adding the decking boards.  For this you’ll need a load of decking screws and an impact driver.  You can use a normal drill drive but using an impact driver at this point really speeds up the process.  I used 10 screws per board to ensure a good solid fit and prevent any movement.  One either side of the board and 5 down the length of the board ensuring I hit the frame underneath each time.  I created a couple of 3mm spacers that I inserted between each board as I secured it to the frame. 

This allows a nice even space between each board.  When inserting each screw please ensure there are no splinters sticking out by removing them with your hand or sanding off.  These can be really nasty if walking around in bare feet.  It’s worth having a pair of knee pads when laying the boards as you’ll be moving around constantly on your knees.  I found out the hard way!

Use a jigsaw to cut around any objects. (Like my veranda supports)

Step 7.  Completing the decking surface

Repeat this process throughout the whole decking frame. You might find you have a little overhang at one end like me but this was fine.  You can always shorten a board with a table saw or circular saw if required.

Step 8. A light sand

Give the decking a light sanding to remove any splinters or rough edges.  Use a 80 grit followed by a 120 (or 200) grit on an orbital sander to give a nice finish.

Step 9. Treating your decking

It’s very important to treat your decking timber as soon as possible after completion.  This will protect it from the weather and the likelihood of rotting.  These spruce or pine decking boards can last up to 20 + years if treated correctly, treated regularly (once a year or every couple of years) and don’t have stagnant water on them.

We decided to paint our decking wood with a specific decking paint from Cuprinol.  We used the Cuprinol Anti-slip decking paint – Urban Slate. Decking paint isn’t cheap but it’s well worth the investment to provide a long lasting coat for your decking.

So there we have it.  A simple but effective and good looking decking area.  My decking is just a straight forward rectangle shape but you may wish to go for something a little more complex with angles, railings and steps.  It depends on how confident you feel.

Materials list

• 22 x 4.8m lengths of decking boards (32mm x 120mm)
• 20 x 2.4m 3×2 CLS construction timber (38mm x 47mm)
• 400 x 70mm slim decking screws
• 100 x 80mm wood screws
• Weed control barrier
• 8 x right angled brackets
• 32 x 50mm screws
• 1 x Cuprinol Anti-slip decking paint – Urban slate (2.5L)

Now on to a raised deck.

How to build a raised decking area

This was the second decking area I built in my garden.  A seating area to enjoy sunny evenings and a shaded area to enjoy during hot summer days.  It’s ideal for those of you who are building on uneven or soil surfaces. Again, I’ll just talk about the decking here but feel free to look at my veranda post to see how this covered section was achieved.

This is a picture of the finished article.  I decided to add a planter and roof to this one which really finishes it off.

Step 1.  Levelling and ground prep

Like before you should work out where you want the decking and how big it will be.  Stick to the planning permission restrictions and you’ll never have the council knocking on your door forcing you to take it down. (It does happen)

This is the spot we decided to build the outdoor decking area.  It’s the spot in the garden that gets the last bit of sun for the day so you can enjoy a beverage and watch the sun go down.

Step 2.  Building the decking frame

Once you’ve measured up and your materials are ready it’s time to lay out your frame.  This will allow you to visualise the deck and see what lengths of timber you’re going to need.

Step 3. Fixing decking boards

The decking boards I purchased were 1.8m long so I had to measure out this length from the fence.  I decided to attach a support beam to the back fence posts for the rear support as these were very sturdy. 

I then marked out 3 points to which the front supports would go.  I came back about 200mm to allow for a little overhang on the deck.  I then dug out 3 holes at these locations.  Each hole was about 300mm x 300mm and about 400mm deep.  I put about 50mm of hardcore in the bottom of each and then set each post in the hole with Postcrete.  I use hardcore at the bottom to allow for drainage so the bottom of the post doesn’t sit in stagnant water and rot. 

Pop the post in the hole and pour the Postcrete in around it.  Always use a spirit level when setting the posts.  Postcrete is available as ready to mix 12.5kg bags from most DIY hardware stores.  Simply add water to the mix in a bucket and stir until ready to pour.  I only used one bag for 3 posts.  Just get everything ready before hand as this stuff dries really quickly.  In less than 5 minutes sometimes.  It’s very useful to have someone help with this part but I managed on my own.

As you can see here I had two long posts and one short post at the far left side.  It doesn’t matter if each post is at different heights at this point as you can cut them to size afterwards.

Step 4.  Weed suppression

Before I fixed the frame together I laid out the weed suppression material and built on top of this.  For added protection from water I wrapped the weed material around the frame on the sides and painted the frame.  Poking a couple small holes in the bottom of the material allowed some drainage.  The frame is simply screwed to the posts at the front and back of the deck area.  You can see in the image above I also used a couple of old paving slabs to add some support.  This is only because I used smaller 3×2 support beams.  You can use thicker beams or add more support posts if you wish.

Step 5.  Complete decking boards

Once the frame is complete and secure you can now add the decking boards.  Mine were all 1.8m long so I didn’t need to cut any down.  A nice easy stick and screw.  Again I used 3mm spacers and about 8 screws per board to ensure a good solid fit.

I actually miscalculated the number of boards required here and ended up 2 short of finishing.  Rather than going back to the shop to buy more I decided to use some old oak boards to build a planter at the end.

Step 6.  Decking fascia boards

On this decking I added some fascia boards round the sides to give a nice finish to the decking.  This was simply screwing the boards to the frame.

Step 7. Sanding

Sanding all the edges and gave the deck and nice smooth finish and removed any splinters from the wood where screws had been inserted.

Step 8.  Protecting your wooden decking

Painting the deck was the last step to ensure good protection from the elements.  I added about 3 coats in most areas.

So thats the finished article pretty much.  We’re just waiting on some furniture now and we’re ready for summer!

The final job was to secure the bitumen roofing sheets to some purlins.

Materials for this deck

• 26 x budget decking boards from B&Q – 1.8m
• 12 x 2.4m 3×2 CLS construction timber (38mm x 47mm)
• 3 x 1.8m boards (80mm x 20mm)
• 2 x 2.4m fence posts (75mm x 75mm)
• Some off cuts or scrap wood to make up the rest
• 200 x slim decking screws 70mm
• 80 x 80mm wood screws
• Postcrete (Blue Circle)
• 4 x Bitumen roofing sheets
• 1 x Cuprinol Anti-slip decking paint – Urban slate (2.5L)
• Water (free from tap)

Thanks for reading.  Here are a few common questions regarding decking:

• Q. Can decking be laid on grass?
• A. You can’t lay decking directly onto grass. It will need to be raised slightly so that it is not in contact with the ground. Follow the second decking area instructions above to achieve this.

• Q. Can decking support a hot tub?
• A. Yes, decking can support a hot tub but it will require reinforcing. The weight of a hot tub is extremely heavy and will require a very rigid frame with lots of joists spaced close together. The exact quantity and thickness will depend on the size/weight of the hot tub.

• Q. Can decking be in contact with the house?
• A. Yes, many types of decking construction include a raised platform that is fixed to the side of the house. Support joists will run along the house to aid in the support of frame.

• Q. How far apart should decking joist be?
• A. Please refer to this grid which will show you distances depending on the thickness of the decking boards you have selected.

Decking board size	Distance between joist centres
20.5 x 95mm	300mm
20 138mm	400mm
27 x 144mm	500mm
33 x 120mm	600mm

• Q. How many support posts do I need for a raised decking area?
• A. This will depend on the size of your decking joists. Please take a look here for some usefully information.

Extra reading

Please check out some more of my projects for some home and garden DIY inspiration.

• How to build your own veranda for under £500
• How to build your own under stair drawers for under £100
• How to create a bathroom vanity sink for under £150
• How to build your own shed from scratch