Concrete base for lamp post

[cwhaley]

I'm putting up an aluminium lamp post next month 2.15 metres tall. On the base of it are 3 10mm holes to allow it to be bolted to the ground.

My plan is to dig an 18" deep hole in the ground twice the width of the post, fill with 1:4 cement/sharp sand, allow to set for 2 weeks and then bolt the post into this. I would use ply to get a square shape to the concrete base.

As I've never mixed concrete for this purpose before (i.e. being able to support a post bolted directly into it) please can somebody tell me whether my above plan is suitable or not?

 

[bernardgreen]

On the base of it are 3 10mm holes to allow it to be bolted to the ground

Make a dummy base from ply wood fit bolts to this with nuts above and below the ply wood. The bolt heads being 6 inches at least from the wood,

Fill the hole with concrete and then put the dummy base on top with the bolt heads submerged into the concrete.

Ensure the dummy base is level and cannot move until the concrete is set.

 

[cwhaley]

Make a dummy base from ply wood fit bolts to this with nuts above and below the ply wood. The bolt heads being 6 inches at least from the wood,

Fill the hole with concrete and then put the dummy base on top with the bolt heads submerged into the concrete.

Ensure the dummy base is level and cannot move until the concrete is set.

Thanks for the idea - hadn't considered a dummy base.

So that I understand correctly, are you suggesting I cut a plywood base to the same shape as the lamp post base, fit three bolts through the timber in appropriate positions (with a nut either side of the ply to hold it in place) then place upside down onto fresh concrete so that the bolt head goes into the concrete?

If so that sounds a good idea. Will have to ditch the pre-packaged bolts that came with it though as they are pathetic.

 

[Ian H]

I’d do the hole 24” square and use ballast instead of sand.

You could set the bolts into the concrete first or drill and use some chemical anchor stuff after.

You would want more than just the head in so could set your nuts so there is 4” of the bolt in the concrete and 2” out.

 

[cwhaley]

I’d do the hole 24” square and use ballast instead of sand.

You could set the bolts into the concrete first or drill and use some chemical anchor stuff after.

You would want more than just the head in so could set your nuts so there is 4” of the bolt in the concrete and 2” out.

Thanks. And no I wasn't planning on sinking just the head in. I do have some threaded bars but they are long lengths so I'll measure an 8" length and set these in the concrete and can saw off any excess once done.

I terminated the SWA into an external junction box at the weekend with the glands and the other half said "that's easy it just screws in", so she can do the next 2 including all the cable stripping, earthing the steel wires, connecting the banjo earthing clips, etc.

 

[Ian H]

Thanks. And no I wasn't planning on sinking just the head in.

Sorry, I read your post wrong and had an image of the heads tight against the underside of the ply

Another thing I though would be to make the ply template then cut away as much of it as you can do you can sort of see through it. Or get your missus to do it, that’s what i’d do!!

 

[bernardgreen]

place upside down onto fresh concrete so that the bolt head goes into the concrete?

Yes,

If the lamp post is hollow with the cable going up inside the post then have you thought about putting a duct in the concrete to bring the supply cable into the post from out of the concrete instead going into the post above ground level. A hole in the middle of the template would be needed to allow the end of the duct to be above ground leve;

 

[cwhaley]

Yes,

If the lamp post is hollow with the cable going up inside the post then have you thought about putting a duct in the concrete to bring the supply cable into the post from out of the concrete instead going into the post above ground level. A hole in the middle of the template would be needed to allow the end of the duct to be above ground leve;

Yes I was thinking how I'd do that. Originally I was going to sleeve the cable and run in the concrete but for access in the future I've asked the other half to nip to a builders merchant this week to grab some flexible cable ducting.