Spacing on fence posts

[skidave]

Hi all,

I have just built a retaining wall in the front yard and would now like to build a picket fence behind it. The retaining wall is 3 sleepers wide, starting at 3 high at the left, then 2 high, then 1 high at the right.

My questions are as follows:

The length of the fence is 6700mm. Do I go for 4 posts or 5 posts (4 posts = spacing of 2233mm, while 5 posts = spacing of 1675mm). The palings will be 1200mm high.

Also, should I concrete the posts in at 500m deep below the bottom of the retaining wall?

My main concern is the post spacing at this stage...

[rod1949]

I'd go 5 posts. With the smaller spacings it my stop the sag that one sees in so many picket fences

[skidave]

mmm. not sure. Might look kinda weird with them being so close together...

[addo]

Definitely the 2200 spacing. With your picket height it will otherwise look pretty odd! I'm assuming you'll be using 16-17 90mm pickets when I say that - the 70mm ones might allow the shorter runs...

Plus - one less hole to dig.

Cheers, Adam.

[skidave]

Beauty! Thanks for that.

And what's the best way to work out the spacing for the pickets between the posts so that they're even?

[addo]

What size picket - 90mm?

Shoot for a nominal 140 between centres (ie; 50mm gap).

Deduct one gap from the rail run, then divide the rest by the nominal centres. Round up to the next whole number.

Say you have 2180 rail run (they will not all be perfect, as the posts will move a little). Deduct 50 (one space) and you have 2130.

Now divide 2130 by 140 and you get 15.2, so make it 16 pickets.

Then, consider there is one more gap than pickets. The picket width is non-negotiable. 16 times 90mm is 1440mm.

After you remove that amount from the rail run, you get 740mm. You have to divide that by the number of pickets plus one.

740/17=43½mm

Now you set up a running measure. Add the picket width to the spacing to get 133½mm and butt your tape up to the left post. On the top rail, make the first mark at 133.5, the next at 267, then at 400.5, etc. Your picket lines up flush to the left of your mark. Check the final mark is close to 43½ from the right side post - if not, you've been gaining a little too much with each measurement.

Tack up the end two pickets for each panel, and run a really tight string line across their tops. Set the centre pickets to this stringline and plumb them up - tack top and bottom. Now work outwards towards each post, checking that the spacing at the bottom rail is reasonably close to that of the top rail. It's a fence; it won't be perfect and because you plumbed the centremost pickets yet made the outers parallel to their adjacent posts, some compromises are needed. Try to spread any huge adjustments over three or four pickets.

As a side note, I tack the pickets with the Paslode fixout gun and 38mm C-series brads. Then I drill (skewed and staggered holes) and handnail with 50mm×2.8 gal bullets. With partly dry hardwoods and cypress, this is the only way to avoid splitting. Plus if you make a hash of a run, it's easy to tap the pickets off and set it up again... Much harder when they're gunned down tight! I've attached a picture to show the nailing pattern (you can just imagine the little dots to be where the gun nails went first - I fill over the top).

Regards, Adam.

[skidave]

Ok - I have the posts in - now just a question on the rails.

Should I use 2x 75x3.75 galv bullet heads OR
1x no14 type17 batten screw
per rail fixing to post?

[addo]

Are the rails mortised into the posts?

I like nailing, but predrill usually. Punch them in a touch if you like, and skimcoat with exterior grade filler for a really clean look. Now is also the time to final paint the posts and rails.

Regards, Adam.

[skidave]

Im thinking I might screw the rails.
The shorter ones seem have to twisted slightly which sucks