Drilling deep - and tough - concrete

bilbobaggins

bilbobaggins

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Replies to the earlier thread were helpful. I have a slightly tougher task, and would appreciate any input.

I need to erect over a dozen 4" x 4" fence-posts close adjacent to a rubble and mortar dwarf wall, and I'll need to go down at least 60cm. However, 5 of the posts will need to be sunk into an existing bed of modern concrete which is about 50cm thick, and I need to buy or hire a tool to manage this. Now, I've used 1500 watt SDS tools for drilling fixings' holes satisfactorily, and have several 450mm long bits left.

Apart from spending all April wielding a 6' wrecking bar, is there a better tool I could hire? I have a free 'hire option' with Travis Perkins locally. What about an electric paving breaker?

/forums/images/graemlins/confused.gif
 
If I were you I would get in a core drilling contractor, and get him to core out 150mm dia holes for you, wont cost that much and will save a lot of hastle and heart ache.
If the new posts are goung exactly where the old ones were, then 150mm dia holes are ample as there is already concrete around them.
The corer will need something for the pilot drill to go into to give a guide for the start of the core drill, then get a peice of wood 4"x4" and hammer it into old post hole, or if old post stub is still there then cut it level with the concrete.
Be very careful using a hand held dry diamond core drill, even with a clutch they are famous for braking arms.
 
If it were me I think I would try putting in a steel rod or post about 1 inch diameter into the concrete at then sinking that into the sawn off 4x4.which sits flush with the concrete. olewill
 
If you are in KL I'll pop round in my lunch hour and knock em out for yer, while eating me sarnie in the other hand. We drill 14m dia holes through rock 30m deep 24/7, but our drill cost a zillion quids and each cutter is a grand and we have 74 of em that need changing at least once a month. I thought boating was dear!!!!!!

Serously if its a path the concrete isn't going to be that hard, an electric Kango will do the trick, be sure to get 2 or 3 bits, 1 being a chisel bit. You need more than 1 so you can free another if it gets stuck. Don't be affraid to over break the hole as a 4" at the top will be impossible tobrearout to 4" at the bottom. Once the post is in place you can fill around with sand cement mortar. Once the mortar starts to harden slop it up to the post, so that rain water runs off and away.

The metal post feet mentioned by another poster are good, you will need a percussion drill to install the Hilti type hold down bolts.

Coring is another way of doing it, but could be expensive I'd want 200 quid to turn out with a van, core machine and 6" core to take a 4" post. Unless you want to plane the end down to 4" dia and weaken the post.

I can see a bloody nail plus some sgfjfcjden words around your house this week-end !!!!!!!
 
A couple of years ago I had to put two gate posts into our concrete drive which is 6 to 9" thick. I hired an electric jackhammer. Hole 1 took all of Saturday. Hole 2 took most of Sunday. Most miserable weekend ever. Swore from then on I would always hire tools up to the job or better.

BTW our drive was most definitely laid by a farmer - flints the size of your fist. These are harder than the steel so make sure you get lots!
 
Thanks, guys, for all that.

The holes need to go *outside* my dwarf wall, against the vertical face. The inside, where the old posts are sunk, is much harder of access in places now. So, new holes for bigger posts....

I'm planning to hire a big hydraulic/electric breaker-drill, and get a couple of young lads from the builders' merchant to come and do the painful stuff. With three of us, we ought to be able to make good progress. Once the posts are concreted in, I can fix all the rest in my own good time.....

This does have a 'boaty' bearing, for it's due to accruing 'brownie points' doing chores like this that I get to go sailing when the opportunities arise.

( ps Anyone got a Corribee II, or bigger, they want delivered somewhere warm? /forums/images/graemlins/grin.gif )
 
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