Sinking gate posts into the ground

You have three choices of posts for sinking into the ground, either tanalised softwood posts (available from most builders merchants), sawn green oak posts (more of a specialised product and available from saw mills and timber merchants etc.) and steel posts.

All three types of gate posts come in many thicknesses and widths, the dimensions of the posts vary depending on the width of gates required, the wider the gates, the bigger the posts required to hold them up and also the taller the gates again the bigger the posts need to be- there is no ‘one size’ fits all! For fitting information on the posts please scroll down the page.

Fitting gate posts to a wall? Go here for tips and advice How to fit gate posts to a wall

Tanalised Softwood gate posts

Tanalised softwood gate posts are by far the cheapest option in comparison with Sawn green Oak posts, as the name implies they are softwood and by being tanalised they are pressure treated to protect against rot. If you make any cuts, notches or drill into these posts then further treatment is necessary on the timber you have exposed to maintain the integrity of the tanalised treatment.
You have probably seen these posts yourself as they can be found in fencing and normally have a green-ish or brown-ish tinge and are supplied rough sawn. If you are choosing Softwood gates then by all means go for tanalised softwood posts if the sawn green oak posts are out of your budget. You can paint or stain these once in place but you may not get an exact match when using stain to the colour of your gates due to the colour tinge of the posts. We do not supply tanalised softwood posts, as mentioned you can normally pick these up yourselves from most builders merchants.

Sawn green Oak gate posts

Despite their name, the sawn green oak gate posts are not green in colour – the ‘green’ part of there name refers to the fact that they are air-dried (rather than Kiln dried – you do not sink kiln dried timber into the ground ever!) and are suitable for outdoor use.

How to sink gate posts into the ground

More expensive than the tanalised softwood gate posts but if your budget can afford these then they are well worth it and if you are fitting hardwood gates then we would really recommend these as if you use the Softwood posts you may well find yourself needing to replace rotten softwood posts whilst you Hardwood gates are in excellent condition.
Its always worth getting a coat of paint or stain (again whatever you are using on the gates) on the posts as it does no harm, the only thing to remember with the sawn green oak posts is that they will in time split – this is perfectly normal with green oak and is in no detriment to the strength of the posts. We do supply sawn green oak posts – please contact us for details.

Steel posts

If you would rather use something other than timber posts, then the best option is steel posts. Again as with timber posts there is no real one size fits all for the thickness and width of posts required – it’s all dependent on the width and height of the gates being attached to the posts.

Sinking the posts into the ground

Before fitting the posts into the ground you should ensure the following:

Posts are weather cut on the top (this enables water to run off – see picture above left),

Posts are the correct length (Depth of hole plus gate height plus clearances under the gate),

(i.e. 6ft high gate, with 2 inches clearances and a hole 3ft deep would require a post length of 9ft 2)

Both the tanalised softwood posts and sawn green oak gate posts are sunk into the ground the same way.

How deep should you sink the gate posts into the ground
You need to first dig a hole a good 2ft 6 (760mm) to 3ft (915mm) deep (this gets the base of the post below the level that frost penetrates, once below this level the ground is less likely to move as much! How wide the hole needs to be is again dependent on the size of the post, for a 6″ post (150mm) I would make the hole 18″ square, giving 6″ gap all round the post.
It’s also a good idea to slope the concrete at ground level away from the gate post to act as a water run off.

1- Once your hole is dug, it’s best to place a bit of hardcore/ballast into the bottom of the hole – this ensures any water drains away and helps to stop your posts from rotting. When you’ve placed this in the hole give it a tamp down to compress it – you can use the end of a lump hammer for this.

2 – Place post in hole and check for plumb (level) on one of the faces of the post and one of the edges (always use the same edge and face on the post so you don’t get differing levels!).

How long should my gate posts be?

Tools/Material required –

Spade/Post hole digger
Tape measure,
Spirit level,
Lump hammer,
Concrete,
Hardcore,
Source of clean water,

3 – You can at this stage tack on a couple of braces to the posts, something like 3″ x 1″ will be fine, once attached to the posts drive a couple of pegs into the ground and then attach end of braces to these pegs. These should hold the posts plumb as you fill the hole with concrete (but keep checking for plumb).

4 – Once plumb backfill around post with concrete, tamp down concrete and check for plumb. Do this in stages, backfill with concrete a bit at a time, tamp down and check for plumb each time.

5 – Once the hole has been filled with concrete, check for plumb again. If you’re satisfied that your gate post is plumb then then make sure braces/props are still secured in position.

Sinking two gate posts into the ground?

If sinking two posts into the ground (one post each side of the opening) then fit your first post as mentioned above. Once the first post is in place cut a length of timber (something like 2″ x 1″ ) to the overall width of the gate (or gates) plus the clearances required between the gates and gate posts. This staff then gives you the distance needed between posts and the positions of the gate posts can be quickly checked as you concrete the second post within the hole. Again once both gate posts are plumb, prop/brace them to keep them in position until the concrete is dry.

How long till the concrete is dry?

It will normally be dry within 24 hours but I would tend to give it 48 hours before hanging the gates off the posts. A lot will depend on how warm the weather is and the humidity – if in doubt give it a bit longer!

More gate fitting tips – Wooden gate fitting guide
Fixing a gate post to a wall – How to fit a gate post to a wall

8 thoughts on “How to fix gate posts into the ground

  1. butcher says:

    I want to install wooden driveway gates.10′ (w)x 6′(h) how thick a wooden wall plate do I need?
    Also what size Thickness would be needed as one side will be attached to a wooden post concreted into the ground. I obviously don’t no what size gate I exactly need until these are in place.
    many thanks.

    1. If the posts are being fixed to a wall rather than sunk into the ground, then the posts only really have to big enough to fix the hinge plate to, as the posts are only as strong as the fixing to the wall!

      Make sure it is well secured to the wall and you’ll be fine with something like 2″ / 50mm thick (assuming your hinges will fit onto this) x whatever the thickness of the gate is.

      Assuming your gates are a 50/50 split, then for the post into the ground I’d aim for at least a 7 inch square post – maybe more depending on the timber you choose for the gates (i.e. if you went for Oak gates then I’d increase the post size).

      Hope that helps!
      Jon

  2. Luke says:

    Hi, I have a 6 foot 6 inch gate. What size gate posts do I need and what depth do they need to be in the ground to ensure that they are secure and will not fall down?

    Many thanks

    Luke

    1. Post size would depend on weight of gates as well as width and height, from the limited info you’ve sent for lighter weight gates I’d say at least a 8 inch square post. However if the gate is Oak or a similar dense timber then you’ll need bigger posts.

  3. craig says:

    i have some 6ft high 100mm galvanized steel posts one fixed to the house wall and one is set in concrete what is the best way to fix wooden gates to them i cant seem to find anything suitable.
    thanks

    1. Either self tapping screws or try bolting the wooden post to the steel.

  4. Graham says:

    Hi John
    Fitting a gate 3ft wide x4ft high 1 post in ground 1 on wall
    Posts are 3×3
    2 questions,
    1 What depth hole would you recommend ( using postcrete)
    2 What size fixing for wall either mason bolt or frame fixing

    Cheers
    Graham

    1. Hi Graham,

      Post depth of 3ft. For the masonry bolts around 130mm unless you are sinking them in fairly deep in which case shorter!

      J

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