Deck foundations

21 Mar 2008
Reaction score
United Kingdom

Building a deck this summer 3.66m x 4.0m using 22mmx145mm hardwood deck boards but wondering which type of founds to use.

The deck will be attached to the house below the dpc at ground level.

The ground then slops away for a fall of 4 inch to the front of the deck
The ground underneath is pretty soft and peaty.

Would laying a 2 inch thick paving slabs on to a leveled and hardcored base with a pre-cast pier placed on top be sufficiant instead of using support posts around the structure.

Also thinking of using 2 inchx4 inch for the framework and the joists, would this be sufficiant.

Thanks for the help
Sponsored Links
no idea, but i can tell you Tommy Walsh (Ground Force) puts down a large grey building brick (see, said i had no idea) on a mortar bed for some decking legs to stand on
Any method can be used, so long as it won't move afterwards. Now that might sound like I am being clever, but its true - think in those terms and you won't go wrong.

Will your slabs move under the legs? Depends on what they are sitting on.

Will a concrete block in the ground with a leg down onto it? Possibly - depends on what lies beneath.

A concreted in leg might still move, if it was into soft clay or even top soil, for example.

What i am saying, there is no one answer. Most methods work if the prep is right to start with.

Top tip is to have as many supports as you can be bothered to build, as this helps to spread the load.

remember, though, don't over-engineer it.
Remember, though, don't over-engineer it.
Hmmmnnnn ... An interesting thing to say, perhaps you could explain what you mean by this wabbit.
Sponsored Links
if previous questions and comments answered by wabbitpoo and myself are anything to go by, he is probably pointing to the fact that when people build them for the first time they go way over the top in terms of what is actually needed to support the deck, and usually end up putting a lot of unecessary work and materials.
Wot he said.

On top of that, its easy to get bogged down with the perceived intricacies of building a deck. My advice is to start thinking about it from the deck boards down, not from the legs up. "So, here are some boards - now how would it be easiest and safest to attach them to the ground?"

Most people worry about concrete, posts, noggins, etc before really thinking it through.

Keep it simple, and use logic.
I don't have a problem with that approach for the majority of ground level decks OP's generally ask about on this forum Wabbitpoo.

If it is expected to be structurally sound though and over 3 or 4 feet high attention to the infrastructure is far more important and your approach less sound.

For raised decks, once the layout of the boards has been agreed (direction and patterns) the design process should start from the ground up IMO ... Posts, Beams and ledger, Joists, Noggins and Boards.

I hear what you say about over-engineering Thermo but (aside from cost) its not a bad trait for a DIY'er when it comes to raised decks needing to be structurally sound ... It will never make things worse ;)

the point both of us are making is that many posters get tied up in knots and confused, and completely over engineer decks, which in the main only need a very simple design.
And, as I've said Thermo, for simple designs I agree with you. :LOL:

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links