pad for scope

[speach]

I'm about to start digging a hole for the concrete pad for my pier. I was wondering how big it should be? I was thinking that a .5 cu/m of concrete should suffice so if that's how big it needs to be? Would a 1 m x .5 m x .5m or a .79m x.79m x .79m be better. Do you all think that a .5 cu/m pad is to big?

[iapa]

I've often seen 1 cubic metre mooted.

However, I asked our youngest and she has suggested I'd probably only need 1' deep with a 3' x 3' base.

 

[sloz1664]

Here in the UK the emphasis is to go overboard at one cubic metre. When I dug my pier pad I dug 0.75 [removed word] but it ended up larger than that due to sides collapsing.  .79m x.79m x .79m should be ideal if your substrate is firm. You can always drive in rebar at varying angles to reinforce the structure.

Steve

 

[RayD]

It depends what you are intending on putting on top of it, and the type of ground you're going in to.

I have just made a 1m3 base as I knew I was going to have a dual rig with a heavy mount, and as I image DSO's, want no chance of anything moving, shifting or vibrating.  However, it's unlikely this is absolutely essential but I was digging anyway so kept going.

Don't forget this isn't a structural element, so it isn't about the strength of the base, it is purely about mass and weight and the ability to keep your OTA perfectly still.

[laser_jock99]

1m3 is probably overkill for most amatuer rigs unless you live in swamp. I'd probably go with your 0.79m3 option and as sugested above a few lengths of rebar driven down in different directions.

I was lucky- straight down onto solid rock, couldn't dig a huge hole anyway.

[The storm fisherman]

16 hours ago, laser_jock99 said:

1m3 is probably overkill for most amatuer rigs unless you live in swamp. I'd probably go with your 0.79m3 option and as sugested above a few lengths of rebar driven down in different directions.

I was lucky- straight down onto solid rock, couldn't dig a huge hole anyway.

I vouch for that after constructing my base last year we have very sandy soil and I constructed a .75m3  pier on a block but I could have easily got away with a 0.5m3 size. you are better to have a deeper hole rather than a lager square  more of mother to push against . my experience from erecting 40- 50 ft ham radio lattice masts.

[saac]

Mine is approximately 0.5 cubic metres  in clay soil.  It is certainly not a structural issue - you could tether a Boeing 747 to a cubic metre concrete base and sleep easy  I have a metal pier bolted to the pad that carriers the AZEQ6, installed about 3 years now and no concerns on movement/vibrations. My advice is don't overthink it, if it looks right it invariably will be.

Jim

[Daz69]

My old dad built his ground floor extension to his house on 1m foundations 30 years ago, and that's still standing without any cracks! As stated previously, it's about steadiness. Even 0.5m far exceeds the requirement IMO. When I get to do mine, I'd go about 1ft deep on a 2ftx2ft pad with angle iron or rebar in the mix. Don't forget to put DPC sheet around the hole first to stop the damp creeping in.