Existing slab

[Octane (Humayun)]

Hi all,

I have an existing slab of concrete in the backyard.

It is about 3.5m x 2.5m and about 5" deep.

I have a pier that I bought off Lewis with four standard 13mm holes drilled through the base for installation.

What is the best way of installing it to the slab?

Do I hire a hammer drill, drill the holes and then just nut and bolt it into place?

Or, am I better off putting a new slab in especially for the pier?

Advice gratefully received.

H

[glend (Glen)]

Unless the slab is cracked into sections I'd be bolting directly to it. Do you know if it was reinforced when poured? Dynabolts would be best but don't drill right through the slab and into the dirt underneath, I did that once. Some people will say that by bolting to a slab that your walking on you will induce vibration into the pier, and thus you should cut out the centre and dig down and set the pier into a purpose poured base completely detached from the floor. How obsessive are you?

[Octane (Humayun)]

Hi Glen,

My wife just told me that the slab is reinforced.

I'm not too obsessive as it will be a remotely controlled setup. The only time I'll have to walk on it is to remove the cover.

I'll look at dynabolting.

Thank you.

H

[LewisM]

I have a hammer drill - you buy the masonary drill bit and the dynabolts (all from Bunnings -just down the road from you) and we can have a crack at it one day. Let me know.

[MrB (Simon)]

Yep, dynabolts. Go for it!

[Octane (Humayun)]

Lewis, that is absolutely fantastic!

How about this weekend?

Cheers, guys!

H

[Octane (Humayun)]

Lewis,

Do I buy a 13mm masonry drill bit? And, the same in Dynabolts?

Cheers!

H

[Octane (Humayun)]

Looks like the Dynabolts come in 12mm. That should do it.

Same sized masonry bit, too, then, I take it?

H

[DavidU (Dave)]

http://img.docstoccdn.com/thumb/orig/128237292.png

cheers Dave

[mozzie (Peter)]

Yep h!! Same size 12 mm drill bit...buy them 75 mm in length when you have drilled the holes have a piece of garden hose around 500mm put some protective glasses on and blow the fine cement dust out of holes to give a better bit into the concrete with the dyna bolts...
Know building houses all the time I have seen dyna bolts with a Allen key depression in the top of the dyna bolts these are fantastic as you use the Allen key and the spanner to tighten till the dyna bolt bits in ( man they are a pain when they start to spin...)...i haven't seen these dyna bolts here in nsw for sale but a project building mob come down from qld and we're using these.best thing I'd ever seen...
Just see if there up there in masters or bunnings...also galvanised are better

[mswhin63 (Malcolm)]

If you are looking for another solution I have used concrete anchors in the past preferring them to Dyno Bolts.

http://www.ramset.com.au/Product/Det...rew-In-Anchors

They are available at Bunnings too.I used them in install some very heavy booths and were subject to heavy vandalism for quite sometime and still standing.

There are even heavier duty bolts as well but not sure if they are available in local stores

[Octane (Humayun)]

David, Malcolm and Peter,

Thank you, so much. You've all been very helpful.

I look forward to having a pier setup this weekend!

The missus has given me the go ahead to use the whole slab and build an observatory. I said I'd look into that later.

H

[sn1987a (Barry)]

Another option to consider is a tube of Sika Anchorfix and threaded rod cut to size. Dyna bolts are quick and easy but the disadvantage of them is that over time they can crack the concrete. Dynabolts are rarely allowed on the concrete construction sites I work on for this reason. The Anchorfix is fast curing and works a treat.

[Octane (Humayun)]

Barry,

Thanks, heaps for that recommendation.

How long does it take for AnchorFix to cure?

H

[sn1987a (Barry)]

http://www.industrialsupplies.com.au...orfix1_tds.pdf

Depends on the temperature roughly about half an hour but on a hot day you have to be quick lol.
When I use this stuff I get all the holes and studs ready then cut the end off attach the mixer tube and give two or three squirts onto the ground to make sure its mixing correctly. Usually the last squirt is correct then go ahead and put it in the holes then slowly twirl in the studs. You can tell from the squirt on the ground when its gone off.

[mozzie (Peter)]

Chemset and threaded rod is also a great option..simple to use ordinary silicon gun....we use this system with n12 steel when having to raise a concrete block wall and more vertical steel is added every 400mm we drill and glue...
I,m no scientist but some of this chemical reaction stuff is amazing!!!
Bit of a funny story glueing steel into concrete around a swimming pool and I had one of these tubes spew it's contents all over me and into my eyes man they started to burn so I just dived into the pool with my eyes open it diluted the chemicals and I was bloody lucky..left slight burns on my skin..

[ZeroID (Brent)]

WooHoo, another SkySlab !!
My 'pier' is anchored to a 4m x 4.5m existing slab in the back yard. The pier is a 900 mm long piece of 250mm diameter concrete water pipe stood on end. It is anchored by a 1 meter long 12mm threaded rod to a single dyna bolt through the slab.
The Observatory sits on 4 corner blocks and isolated from the mount although on the same slab. There is enough mass and stability to minimise any vibration and when I'm in there I don't move much anyway. And the slab is stuck onto the side of a volcano, if that moves I won't be around to worry about vibrations !!

Go for it H, you will never regret it.

[el_draco (Rom)]

Id be interested to hear from anyone who has built a domes on a slab and bolted the pier to the slab without isolation.... Dilemma I face

Is there measurable vibration? What about wind induced vibration through the dome?

Counter intuitive.

[LewisM]

H, I will consult the Walking Filofax (aka the wife) and get back with you. Sunday at least should not be a problem.

Now I got to find the drill in my maze of a garage since moving. I have a good idea where it is, seeing I installed 2 gunsafes with 12mm x 75 dynabolts when we moved in

[Octane (Humayun)]

OK!

Saturday or Sunday will be fine. We're not going out this weekend.

I'll head to Bunnings on Saturday morning. Just let me know what drill bit to get.

H