Fence posts - help

[griffin]

Advice please, I am trying to work out how to replace an old fence. Currently 3ft panels that are held with Metposts but are all wonky (wobbly and not lined up!) and very poor quality. I want to replace using 6 foot panels and 8ft posts but am having severe dificulty digging to a 2 foot depth for concrete. I want the posts in slightly different places to the original to incorporate a gate but the ground in on a slope, the rocks are big and (the most awkward) is that there are numerous big trees nearby with extensive root systems.
IF I can dig a 2 ft hole it'll end up being about 1 or 2 feet in diameter (digging round the rocks etc). When I get to this stage what do I do? all the tutorials say dig a deep straight sided hole but clearly this isn't possible. Should I just mix lots of concrete or fill with hardcore/dirt and hope for the best (maybe concrete in the old metposts)?
Something so simple has turned into a mare, please help

 

[GwaiLo]

You could make concrete bases and then use bolt down metposts.

However, you need to get the side as vertical as possible or the posts are less likely to stay upright.

 

[MANDATE]

Based on my limited experience I would advise thet regardless of the hole diam. it is better to have vertical sides so there is something for the post to push against when under pressure from wind.
Well packed hard core should suffice for filling in except for the top 4 to 6 ins. which should be concrete.
Concentrate on the two outermost posts first to get them correct for height, orientation and vertical.
Concrete these and leave to set overnight.
You will find it easier to fit a panel with another post now you have a post already fixed, the panel which can be supported helps to keep the next post upright and in the correct position while the concrete is setting.
The position of your gate will most likely mean one or two panels will have to be shortened and take into consideration what the gate is going to hinge on, you will have to secure timber to each gate post.
Do make sure the posts for the gates are parallel by fitting timber between while the concrete is setting.

 

[griffin]

Thanks Guys, I dont think the first suggestion will work for me as I dont really have the space for a concrete base. If there is a need for vertical sides these will have to be 'manufactured' rather than dug.
If I dig the hole as best I can then put something like a piece of drain vertically into it then fill the edges with hardcore/dirt then remove the tube to leave a hole for the post (and concrete) do you think it'll work (harder to explain than I thought !). An added complication is uneven ground so I may have to build up th sides anyway.
ASCII art picture to try and explain below.
XXX- concrete
...... - dirt/hardcore
------ ground
| | - tube to leave a hole for post

xxx | |xxxx
XXXX| |XXXX/------------------------
---------------\ ....| |.... /
\ ...| |... /
\----------/

Thnaks for the advice so far.

 

[masona]

then remove the tube to leave a hole for the post (and concrete) do you think it'll work .

No,I don't think it will and depending how big the tube is as well. The 8' fence panel could blow over in high wind and the post need to be in a lot stronger position than ever.You'll be better off using concrete fully and put in a small amount of hardcore with the concrete at the same time.For your concrete,you will need 3/4" ballast sand with cement and if need be you can get Rapid Cement for quicker drying.

 

[DavidH]

If your holes are too big then you will spend a long time mixing concrete. If you have some old timber you could make some shuttering to form a square of the right size and then backfill once its all dry.

I would also suggest using a string line from the first to last post to ensure that they are all nicely lined up.

 

[MANDATE]

I think you could use a tube and there would be no need to remove it, but you're looking for something in the order of 9 in min inside diam.
Masona may amend his reply when he realizes the panels are not 8 ft.but I agree the wind is mighty strong.

I assume you will have 1 ft high 'pre cast gravel board' so the panels are in fact 5 ft making a total height of 6 ft.

If the wind is from one general direction I suppose if it was a square hole only one side needs to be fairly vertical, that would be the side the post would move towards when the wind affects it. The bottom of the post is less likely to move.
There are of course special tools to help this type of work. I have used a 4 ft long by 9 in diam. post borer by hand which gives a neat hole providing there no obstructions.
Also I have used a spade with a tapered blade which is about 20 ins deep.

 

[masona]

Masona may amend his reply when he realizes the panels are not 8 ft.but I agree the wind is mighty strong.

It is 8' high when you're carry it then 6' when slotted in post.

 

[griffin]

Oh dear, I think I'm getting out of my depth a little here. Pre-cast gravel board ............... not sure what it is but I wasn't going to use it. My intention was to put up some posts then attach some fence panels. Sounded simple.
Having dug about (haha) on the net a bit, I assume gravel boards are placed on the ground between posts and then the fence panels rest on them?
I guess that they will help with preventing rot but are they really necessary, I really needed this to be a cheap(ish) job. Also because of having to incorporate a gate the distance between posts wont be standard so I'd have to cut them which sounds even more complicated.


Current position is I have now managed to dig out a hole (one of many but hopefully the most difficult!)which is about 2 feet deep, it has reasonable vertical sides but is about 18 inches wide. Is the concensus that I put some hardcore in the bottom, rest my post on it then fill the whole lot with concrete (taking into account whats been said about positioning etc on this and othe fence threads)?

Just a comment on tools, the ground is just not suitable for post diggers etc. It has taken me literally 4+ hours with a pick, a crowbar and a spade to get to where I am now (1 hole!) The rubble, stones and tree roots are a major pain.

Thankyou for your help so far it really is appreciated.

 

[masona]

I assume gravel boards are placed on the ground between posts and then the fence panels rest on them?

Yes and the gravel board will stop the bottom of your fence panel rotting if it is touching the soil surface.What is the cost for a 6'panel against a 5' panel with 1' gravel ? properly not as expensive as you think but you will need to borrow or hire a 9" grinder & cutting disc to cut your gravel board.

Is the concensus that I put some hardcore in the bottom, rest my post on it then fill the whole lot with concrete (taking into account whats been said about positioning etc on this and othe fence threads)?

Yes !

The rubble, stones and tree roots are a major pain.

To make you feel better , I've managed to hit seventeen tree roots,bricks,stones out of 22 holes !

 

[MANDATE]

Hi Griffin.
I think I may have made an assumtion you intended to fit concrete posts but reading your query again I can see it could be wooden posts you intend to fit.
The gravel boards are like you say to prevent the panels rotting, 3 or 4 in. wooden boards were used before concrete post came out and it was easier and cheaper to replace these instead of the panels. With concrete posts you have the concrete gravel board. Cost wise I think they are around £3 each and a 5ft panel will be less than a 6 ft panel so there should little difference in overall cost.
If you are using wooden posts I would advise painting the portion that is below ground level with a bitumen paint.
On the other hand you can get concrete posts where only 2 1/2 ft protrudes above ground level and wooden posts can be bolted to the concrete. this stops the posts from rotting.
With the full height concrete posts fixing the gravel boards and panels is simple, you don't put the posts up and slide the panel in from the top.
You fix a post, then place gravel board and panel into position and position second post, then the second gravel board and panel and position third post and so on.
The disadvantage with concrete posts is you can't hammer them and I did find some hairline cracks.
I would advise using the panels to set the distance between posts which would mean shortening a panel or maybe two would only apply adjacent to the gate.

 

[Scoby_Beasley]

As an addendum (big word eh ?? ) the part of a post that rots is the top 6"-9" in the ground, this is where all the organisms live/breed/party, that's why you struggle to get the other 15"-18" out the ground, it's still solid wood.
Here endeth the lesson, Thankyou David Bellamy.
Amen

 

[griffin]

What a helpful lot !
I'm going to keep digging until the first section of fence (6 holes) are dug and then see what options I have. I'm nervous about concrete posts as (I assume) they need to be really accurate wheras I imagine wood ones are a bit easier to alter (eg screwing battons to etc).
I think I need to use gravel boards - never even crossed my mind but sounds like a good idea, wooden posts = wooden gravelboards?

As I only have limited time it's going to take a while but no doubt I shall be back on this board for more help sometime soon.

Thanks everyone

 

[masona]

I'm nervous about concrete posts as (I assume) they need to be really accurate

It's not as difficult as you think for leveling,just heavy work specially with the holes have to be the right depth. The good thing about concrete post/gravel,you only have to fitted it once !