DIY Decking | Part 1 – Planning & Design

decking planks laid away from the camera with a bench in the background and sams new fence
My decking just after completion, before the kids trashed it!

This guide covers all the steps to confidently take you from thinking “I know, I want a deck”, to actually having some concept plans that look great and are drawn to scale. Read on folks and soak it up! If you have any suggestions or edits, let me know

Jump straight to…

I’d be very surprised if your decking was exactly the same as mine. Therefore, I’ll try to keep things as generic as I can and make sure I explain how to do things that apply to all decking, not just mine.

Do I need Planning Permission for a deck?

First off, we need to check what we’re allowed to do. That’s right folks, decking falls within planning rules…

Planning rules place restrictions on the size of a deck. At the time of writing, the decking is considered “permitted development” if it:

“is no more than 30cm above the ground

together with other extensions, outbuildings etc, covers no more than 50 per cent of the garden area.”

Source: Interactive House, England’s Planning Portal

Permitted development means the build is allowed without having to seek planning permission.

In addition,

“Building Regulations should be assumed to apply to every deck structure requiring planning permission.”

Source: Interactive House, England’s Planning Portal

Right then, now that we’ve got that annoying bit out the way with, let get cracking. As with most things, we need to plan the deck first and I’ll take you through the things you need to think about. All to get the most out of your deck.

Firstly, we’ll run through the most basic requirements.

What Decking Material shall I Use?

Well, that’s totally up to you. There’s loads! From natural products (hardwoods & softwoods) to manufactured products that look like plastic or are intended to mimic natural boards. The type you see in my pictures is a very hard wood called Yellow Balau. It’s very very dense (about twice as dense as pine), which is why I like it. It doesn’t necessarily require maintenance, just a light jet wash once or twice a year to keep it clean as a minimum. Like most woods, it goes silver within a few years and will probably outlast the frame.

Choosing the deck boards is a blog post in itself, so until I produce that I’m afraid you’ll have to do you’re own research, but here are a few pointers to consider:

Decking Maintenance

Manufactured decking is undoubtedly best for low maintenance decks….. Or is it? I’ve installed a few in my day job and (I shall not name and shame here, tempting as it is) we have used THE most expensive artificial decking supplier in the UK. At something like £90 per square meter at the time, it was ridiculously expensive. And, we had problems. I’m not saying this is the same for all manufactured decking solutions, but be weary. Bear in mind how long the product has been tested in the market, does it come with an insurance backed guarantee? Do your research, check the age of online reviews to see how long it’s been around.

Decking Aesthetics

This one’s up to you. I love the look of wood and the way it weathers over time. The silvering and cracking as the sun bakes it only enhances its appearance as far as I’m concerned. But that’s me, not you. If you’re struggling to decide how you want it to look, hop onto Pinterest or Google and start browsing decking pictures, it won’t take long before something jumps out at you and feels right. If you don’t like the idea of the material weathering, then some sort of manufactured decking with a long guarantee will probably suit you best.

Decking Screws & Fixings

The type of deck board dictates the type of fixings, and if the fixings are visible, they form part of the decking aesthetics. With mine, Yellow Balau requires a stainless steel screw at a rate of two screws per joist at every joist location. The heads of the screws also need to be quite large. This is due to the forces that Balau creates when it tries to twist and bend over time. If the screws had small heads, the boards would simply “pop” off the screw shaft. With the deck screw heads being so visible, they needed to look neat and line up, like so:

a couple of decking boards with a stringline going over the top, which is lined up with the joist below. There are four screw heads showing (two per board) that are in-line with the screw heads
I used a stringline to set the position of my screws before drilling them in

Many artificial decks have concealed fixings, usually hidden in the gaps between the boards. Millboard, for example, manufacture the outer layer of their board with a soft, rubbery material so that once a screw head has been buried several millimeters below the surface, the board material closes up to conceal the screw head. Genius! except I’ve found it doesn’t always close up, bugger!

Decking Cost

Finally, the cost of decking varies from about £7 per square meter of really basic softwood (pine) boards to £100 per square meter of some artificial decking. Clearly, the cheap softwood wouldn’t last too long, but does it need to? When considering cost, you have to weigh it up against the benefit, this is called value for money. If you’re moving house in 2 years, do you need a £100 per square meter deck (plus the cost of fixings) that comes with a 25-30 year guarantee?

Sizing Your Deck, is it Big Enough?

The size of the deck depends on how you want to use it. If you plan on having a three piece Rattan furniture set with corner sofa, then you’ll likely need a good deal of space. Have a think about the following:

  • Will you be entertaining guests? Such as for BBQ’s, evening meals or just a catch-up with a friend. If so, how many will it be for?
  • Existing garden furniture – if this is to go on the decking, measure it up so you can sketch it onto your plans.
  • With estimating the space that a table and chair use up, you need to account for the chairs being pushed back from the table, pushed back some more, and then someone walking around the back of the table. As a general rule, 1.5m out from the table edge works quite well.

The diagram below shows a typical two chair and small table arrangement, perfect for afternoon tea with a friend. There’s no need for anyone to walk around the back of the chairs, so the furniture doesn’t take up too much room:

plan on decking showing small table and two chairs. decking dimensions measure 2.2m by 1.2m

The next one shows a smallish table with 6 chairs, perfect for a BBQ & drinking session with a few friends. Extra decking space should be made available around the rear of the chairs if possible, to allow people to get to every chair. You can really see how this bumps up the decking area considerably.

top down view on 6 seater table, with the decking outer dimensions measuring 4.53m by 3.73m

I’ve drawn two outer lines on this one above. Whilst the outer 4.53m x 3.73m is ideal, the inner measurements are the absolute minimum, anything less and the deck will be too small and your good lady risks falling off the deck spilling Prosecco all over the flowers. Whilst that would be hilarious, it would also be a terrible waste of Prosecco! Building this deck to the outer line provides enough room for people to walk around the back of the chairs whilst those chairs are pushed out.

Anyway, once you’ve thought about these considerations, you’ll have worked out the minimum size the decking needs to be. Now it’s time to check this minimum size fits in the area you have available.

Regardless of whether it does or doesn’t fit, I strongly recommend surveying the area. We’ll cover this next.

Surveying the Area of Decking

It will help a lot if you could draw everything to scale. If you’re unsure how to do this, check out my other How-To on Making a Scalable Drawing.

I installed my decking in the far corner of my garden, pretty much up against the fence on two sides.

decking planks laid away from the camera with a bench in the background and sams new fence
I still had some low shrubs to plant on the left to tidy things up a bit

Therefore, I surveyed the fence position and its posts. The post positions were crucial because I intended to use them to prop up half my decking frame.

plan showing fence in the corner of the garden

I also measured the position of the surrounding shrubs and trees because I wanted my decking to be built up against these.

surveyed shrubs and the fence ahead of the decking design

Once drawn up, I had a plan to work with, showing everything that was already there. With this, I can put pen to paper and start on some conceptual designs.

Designing Your Deck – Levels and Steps

Design isn’t just about the layout of the deck, another consideration is the intended height of the deck, or heights if you plan on building multiple levels. For me, the ground levels were raised towards the back corner and these levels couldn’t be lowered without significantly altering the fence. Given that I’ve not long built the fence, I didn’t fancy altering its level.

I wanted my decking to be raised anyway to give a better level to look over the garden. With these two things in mind, I felt that 450mm up from the surrounding ground levels would suffice.

With the decking raised above ground level, I’ll need steps going up to it. Three at 150mm height each will do nicely to make that 450mm level change from ground level to deck.

two sets of steps for sams decking platform curved construction
Both sets of curved steps under construction

Steps are often seen as something of a necessity and nothing more, however they can add to the aesthetics of a project. I would recommend using steps as an “entrance” to your deck, even if it doesn’t necessarily need it (that’s if you can be bothered with the extra work)

Helpful Tip – 150mm step height is standard and complies with building regulations.

That said, steps need to be carefully considered and need to look the part.

Decking steps don’t necessarily have to be at the entrance to your decking, they can be integrated at any point throughout the deck. For instance, the back corner of my deck had to be higher than the rest, because this was over the highest ground levels. I could’ve build half the deck at this higher level, with the rest at a lower level.

However, I kept the deck at one level throughout (not including the entrance steps) because this maximises the available area to use. If I were to split the deck into two levels, this would greatly reduce the usable space on the deck due to there being a step to split up the two levels. My deck simply isn’t big enough to split into two levels, but I can see the appeal for larger decks.

Designing Your Deck – Sketching Layouts

Back to the design –  At this stage, just sketch some top down views on the decking. I did a couple of variations for my family to consider.

For me, it was clear that the deck would meet the fence, that’s a no brainer! The only variations for the remaining part were to what extent it would stretch along the rear boundary. So I came up with these two options:

DECKING CONCEPT OPTION 1

plan showing decking concept option 1 with two sets of steps. This is the smaller of the two options
Option 1 is quite a small decking area – about a 4m radius from the corner

DECKING CONCEPT OPTION 2

DECKING CONCEPTS OPTION 2 is the larger of the two concepts, again with two sets of steps
Option 2 is only slightly larger than the first, but utilises the space a bit better

Option 2 is obviously more costly that the first. However, option 1 leaves an area of ground behind the centre tree that’s useless. So we concluded on building option 2.

Notice also that I’ve added levels to the plans. 0.00m being the existing ground level, with 0.15m high steps leading up to the main decking level at 0.45m high.

Deck Board Orientation

Another major consideration is the orientation of the deck boards. Have a think about which way you want them to span – left to right, front to back or diagonally. Diagonally orientated boards creates a lot more work, mainly due to the fact that each end will have to be cut at an angle, which has to be accurate to ensure a straight edge. The joist ends will also need to be cut at an angle too (the joists tend to run perpendicular to the deck boards by the way, we’ll cover that in part 2 – the structural design).

Generally, it’s a good idea to orientate your deck boards towards the garden. So if your decking extends from the rear of your house, have the boards running away from the house, towards the rear garden.

Once you’ve got the layout sorted, it’s worth marking out the extents of the decking on the ground. Spray paint is useful here, failing that use anything from pegs to bricks, just so that you can see its expanse on the ground and decide if it’ll be big enough.

If all is good, finalise the plan by drawing it accurately. Add some notes on any ideas you have.

final plan on decking showing the boards, proposed plants, lighting and a bench

Add on a bit of extra detail at this stage too, such as:

  • Lighting
  • Plants, tree’s & shrubs
  • Furniture

You can see how, by adding some detail, it becomes easier to visualise the decking.

In the next part, you’ll use this plan to produce a second plan that’ll show the structural framing and posts beneath, basically making sure it stands up.

Cladding Your Deck

Cladding is the part of the deck that’s vertical, so the sides. This also includes the step risers. On my decking, I decided to clad the step risers and some of the exposed edges with decking boards.

front view on steps showing the decking boards used as risers and cladding
The top riser continues on to form cladding to the left

If any part of the decking is raised above ground level, then it’ll likely need cladding of some sort. I like to go by the rule of thumb that “the simpler the better”, so I clad the sides of my decking using the same decking boards as the top.

And that’s about it for this how-to, I’ve not finalised part 2 yet but will do soon. Part 2 will be about the structural design of decking and will cover the layout of the joists and posts to form the frame, plus joints and fixings.

If you would like to be notified of part 2’s release, feel free to sign up to my email list using the form below.

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