Any builders here? Lamp post foundation question

[Dan Le Moignan]

Afternoon guys.
I have a question regarding fitting a lamp post.
It is 2.3m high so was digging a hole 2ft squared to pour concrete into to fix it to.
I have only dug down approx 6 inches and have hit a concrete slab.
I think the slab was there as the old owners had a bird avery there years ago.
To save breaking it up can I pour concrete straight on top ? Or will that not be as strong as one pour as one section will be sat on top if that makes sense!.

[The Radman]

can you not just move it over slightly and start afresh,thats what id do if poss

[AJC]

What kind of base plate is there on the lamppost? Or is it open ended?

[Dan Le Moignan]

Not really Nick as don't want the post any closer to the drive.
The slab is about 4" thick and looking at old arial pictures about 10ft square I guess so no chance of moving it back either.
May just have to break it out as read now it's not ideal to pour onto old concrete.

[evo1]

i assume you have a base plated post with 4 holes and not a root base one, just pour your new concrete over existing slab and then get some 10/12 mm threaded bar cut at 12 inch lengths, drill down 9 to 10 inches which will go through into old slab as well and chemical fix the threaded studs, job done.

[Dan Le Moignan]

Any builders here? Lamp post foundation question

Sounds good, yes it is a base plate type post.
Could I not drill the old base and insert thread bar first then pour on top so it would act as rebar?

[Darren]

If you're happy that the old concrete is thick enough and there's enough of it then use thunder bolts to bolt the base plate down to the concrete.

If you've not got a base plate on your lamp post then you could break through the concrete, dig down a bit and shove a length of 9 or 12" diameter drain pipe in the hole (vertically) - about 300 - 450mm long should do it. Get some concrete or post mix around the outside of the drain pipe and then once it's set put you new lamp post in the pipe. Plumb it up and gently fill the pipe with either sand or 10mm clean stone. This way when your Doris backs into the post, the post will give a bit and cause less damage to your bumper and wallet

[evo1]

Sounds good, yes it is a base plate type post.
Could I not drill the old base and insert thread bar first then pour on top so it would act as rebar?

Yep, that'll be just as good and easier, but i would still use some R-KEM resin in the old slab, once that sets, which is rapid, just pour the new concrete over top, chemical fixing is far superior and stronger to any rawbolts etc, you can use a normal silicone gun for the resin.

[AJC]

Drill the exisiting slab with a 12mm SDS bit, see how deep it is before you break through. If it's 100mm you're fine.

Resin is a good fixing but you don't need to use resin, get it drilled and if it's thick enough send me your address and i'll post you 4 x M12 Throughbolts. they just knock in and grab on the concrete as you tighten it.

What size holes are in the base plate?

[Dan Le Moignan]

Cheers guys.
Andy the lamp post comes with x4 bolts and plugs that you hammer in first like a rawl plug.
The slab is at least 4" thick but will only cover half the hole.
Was thinking dig the other side out then dig slightly under the old slab and pour the concrete.
Thanks for the offer of bolts etc.

[Dan Le Moignan]

Sorry don't think I explained earlier the iam digging the hole 2ft square and have hit the edge of the slab so I can dig out half of it 2ft deep but other half is taken up by the slab

[AJC]

YEAH BE RIGHT

[evo1]

is it a proper cast iron post or a lightweight allumnium post?, if cast iron and a tall one i would definately use resin to fix the studs in place, the breakout ressistance is far far superior with resin and youll find it far easier, once youve got all the concrete in place and cured for at least 5/6 days, just pop the post base on the concrete drill through the holes on base plate, and simply fill the holes with resin and push the studs in, once set simply wind on the nuts and washers, dont forget to blow out dust from within holes before filling with resin.

[The Radman]

if your digging 2ft down at the side of it then you will see how thick it is anyway,so it may be easier to just break it out and be done with it,if it was only footings for an aviary then i shouldnt think it will take much breaking up

[Dan Le Moignan]

I have already dug down Nick it is about 4" thick.
It is a cast iron lamp post about 21kgs