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Lobster
 
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Default Compacting my hardcore!

I'm about to start laying a new small section of solid floor (approx 1m
x 1.7m) - first time I've ever done this. Think I've extracted from the
uk.d-i-y archives all I need to know, but could someone explain about
requirement for compacting hardcore prior to laying the concrete? I
have excavated about to about 15" below the final surface (it's earth
now), and was going to chuck in 6" hardcore now. Am I supposed to sort
of jump up and down on the hardcore a bit before I blind it with sand?!

Thanks
David
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Grunff
 
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Lobster wrote:
I'm about to start laying a new small section of solid floor (approx 1m
x 1.7m) - first time I've ever done this. Think I've extracted from the
uk.d-i-y archives all I need to know, but could someone explain about
requirement for compacting hardcore prior to laying the concrete? I
have excavated about to about 15" below the final surface (it's earth
now), and was going to chuck in 6" hardcore now. Am I supposed to sort
of jump up and down on the hardcore a bit before I blind it with sand?!



Ideally you need a wacker to compact it. They are quite good fun to use.
Having said that, this is a very small section of floor, and I suspect a
good bit of jumping up and down might be enough.

The reason for doing this is that if you don't compact it sufficiently,
there's a chance of future settlement, which could cause your 1x1.7m
slab to move relative to its surroundings.


--
Grunff
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doozer
 
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Lobster wrote:
I'm about to start laying a new small section of solid floor (approx 1m
x 1.7m) - first time I've ever done this. Think I've extracted from the
uk.d-i-y archives all I need to know, but could someone explain about
requirement for compacting hardcore prior to laying the concrete? I
have excavated about to about 15" below the final surface (it's earth
now), and was going to chuck in 6" hardcore now. Am I supposed to sort
of jump up and down on the hardcore a bit before I blind it with sand?!

Thanks
David


You need a wacker plate. They are heavy (two person lift unless you are
superman) but quite good fun to use. They come in various sizes and you
can get ones that are like a mechanical pogo-stick (probably the most
suitable considering your floor area).

I'm not a builder but considering how much the hardcore compacts when I
have used a wacker plate I wouldn't have thought you could lay a floor
without compacting it first.

If you are feeling poor you can use a post with a bar attached at right
angles to compact small areas but it's really hard, hernia inducing,
work. Jumping up and down on it is practically a waste of time and just
hurts your knees.
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Cant you just use WinZip?

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bugbear
 
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Lobster wrote:

I think divX gives good results ;-)
http://www.divx.com/

BugBear


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Tony Bryer
 
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In article , Lobster
wrote:
Am I supposed to sort of jump up and down on the
hardcore a bit before I blind it with sand?!


As the others have pointed out you need to do a bit more than
jumping on it. You should have nothing bigger than a half brick -
if you have, breaking it up in situ with a sledge hammer will
achieve this and compact it at the same time.

If you're putting a polythene dpm over the blinding it will need
to be free of any roughness. If not putting some light polythene
will stop the grout in the concrete draining through and make
levelling it a lot easier.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser
http://www.sda.co.uk/qsedbuk.htm


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Rick
 
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On Thu, 31 Mar 2005 14:03:54 GMT, Lobster
wrote:

I'm about to start laying a new small section of solid floor (approx 1m
x 1.7m) - first time I've ever done this. Think I've extracted from the
uk.d-i-y archives all I need to know, but could someone explain about
requirement for compacting hardcore prior to laying the concrete? I
have excavated about to about 15" below the final surface (it's earth
now), and was going to chuck in 6" hardcore now. Am I supposed to sort
of jump up and down on the hardcore a bit before I blind it with sand?!

Thanks
David


Others have said how to compact it, the better quality hardcore
(limestone scalpings) will be easier then the cheep stuff (crusher
run). I guess you only need a tonne bag, 25 quid for some good stuff.

9 inches of concerete sounds like quite a bit for a floor, unless you
are building on it.

Leveling the concrete is not so easy, and it can burn if you have too
much skin contact, take care.

Rick

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Dave
 
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Grunff wrote:
Lobster wrote:

I'm about to start laying a new small section of solid floor (approx
1m x 1.7m) - first time I've ever done this. Think I've extracted
from the uk.d-i-y archives all I need to know, but could someone
explain about requirement for compacting hardcore prior to laying the
concrete? I have excavated about to about 15" below the final surface
(it's earth now), and was going to chuck in 6" hardcore now. Am I
supposed to sort of jump up and down on the hardcore a bit before I
blind it with sand?!




Ideally you need a wacker to compact it. They are quite good fun to use.
Having said that, this is a very small section of floor, and I suspect a
good bit of jumping up and down might be enough.

The reason for doing this is that if you don't compact it sufficiently,
there's a chance of future settlement, which could cause your 1x1.7m
slab to move relative to its surroundings.


I have a similar question to the OP

I want to put an 8 by 12 foot shed on an old greenhouse base. I intend
throwing all the various bricks and rubble in the middle and topping it
off with hard core.

Without tamping it down, will I have any serious settlement problems?

Dave
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doozer
 
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Dave wrote:
Grunff wrote:

Lobster wrote:

I'm about to start laying a new small section of solid floor (approx
1m x 1.7m) - first time I've ever done this. Think I've extracted
from the uk.d-i-y archives all I need to know, but could someone
explain about requirement for compacting hardcore prior to laying the
concrete? I have excavated about to about 15" below the final
surface (it's earth now), and was going to chuck in 6" hardcore now.
Am I supposed to sort of jump up and down on the hardcore a bit
before I blind it with sand?!





Ideally you need a wacker to compact it. They are quite good fun to
use. Having said that, this is a very small section of floor, and I
suspect a good bit of jumping up and down might be enough.

The reason for doing this is that if you don't compact it
sufficiently, there's a chance of future settlement, which could cause
your 1x1.7m slab to move relative to its surroundings.



I have a similar question to the OP

I want to put an 8 by 12 foot shed on an old greenhouse base. I intend
throwing all the various bricks and rubble in the middle and topping it
off with hard core.

Without tamping it down, will I have any serious settlement problems?

Dave


Hmmmm. Hard to tell. I have seen a pile (about two tons) of hard core
just left out (suffering nothing more than minimal foot traffic and the
odd wheel barrow) in a layer about 6 to 8 inches thick. It did settle
but not by any where near as much as if it had been tamped down and it
still set hard (as hard core does when it has been tamped). I suspect
that it would have compressed more if it had been put under heavy load
such as having a car drive over it but it was fine for foot traffic and
wheel barrows.


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Rick
 
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On Thu, 31 Mar 2005 18:31:51 +0100, doozer
wrote:

Dave wrote:
Grunff wrote:

Lobster wrote:

I'm about to start laying a new small section of solid floor (approx
1m x 1.7m) - first time I've ever done this. Think I've extracted
from the uk.d-i-y archives all I need to know, but could someone
explain about requirement for compacting hardcore prior to laying the
concrete? I have excavated about to about 15" below the final
surface (it's earth now), and was going to chuck in 6" hardcore now.
Am I supposed to sort of jump up and down on the hardcore a bit
before I blind it with sand?!




Ideally you need a wacker to compact it. They are quite good fun to
use. Having said that, this is a very small section of floor, and I
suspect a good bit of jumping up and down might be enough.

The reason for doing this is that if you don't compact it
sufficiently, there's a chance of future settlement, which could cause
your 1x1.7m slab to move relative to its surroundings.



I have a similar question to the OP

I want to put an 8 by 12 foot shed on an old greenhouse base. I intend
throwing all the various bricks and rubble in the middle and topping it
off with hard core.

Without tamping it down, will I have any serious settlement problems?

Dave


Hmmmm. Hard to tell. I have seen a pile (about two tons) of hard core
just left out (suffering nothing more than minimal foot traffic and the
odd wheel barrow) in a layer about 6 to 8 inches thick. It did settle
but not by any where near as much as if it had been tamped down and it
still set hard (as hard core does when it has been tamped). I suspect
that it would have compressed more if it had been put under heavy load
such as having a car drive over it but it was fine for foot traffic and
wheel barrows.


I have been considering "heavy load", I have observed, my mobile phone
survives being run over by a HUGE 4wd tractor, and my cheep wickes
spade survived a 2 tonne tracked excavator at the weekend, I would
expect neither to survive a my size 10 feet ........

Rick

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Lobster
 
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Rick wrote:
On Thu, 31 Mar 2005 14:03:54 GMT, Lobster
wrote:


I'm about to start laying a new small section of solid floor (approx 1m
x 1.7m) - first time I've ever done this. Think I've extracted from the
uk.d-i-y archives all I need to know, but could someone explain about
requirement for compacting hardcore prior to laying the concrete? I
have excavated about to about 15" below the final surface (it's earth
now), and was going to chuck in 6" hardcore now. Am I supposed to sort
of jump up and down on the hardcore a bit before I blind it with sand?!


Thanks for all the replies. I'd love to play with a 'wacker' but looks
a bit pricey and maybe a bit overkill for my small application. I think
given that the area concerned is going to be at the end of an L-shaped
utility room, most of it will be under units, so shouldn't get too much
loading. Reckon if I use a hand tamper; and maybe screw some rods into
the side of the existing, abutting slab as reinforcement before pouring
the new mix, that would dissuade anything from settling?

9 inches of concerete sounds like quite a bit for a floor, unless you
are building on it.


See above. The deal is that I have an existing, very old, concrete slab
which I'm adding to: BCO wants a DPC, 2" kingspan, then 3" screed which
will bring it all up to the level of the adjacent kitchen. Before that
I'm extending the slab by this extra 1m, ie preparing a new slab to come
up to the level of the old one. So that will be 6" hardcore followed by
4" concrete (then later the DPC, kingspan etc... complicated to explain!)

David
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The Natural Philosopher
 
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Dave wrote:

Grunff wrote:

Lobster wrote:

I'm about to start laying a new small section of solid floor (approx
1m x 1.7m) - first time I've ever done this. Think I've extracted
from the uk.d-i-y archives all I need to know, but could someone
explain about requirement for compacting hardcore prior to laying the
concrete? I have excavated about to about 15" below the final
surface (it's earth now), and was going to chuck in 6" hardcore now.
Am I supposed to sort of jump up and down on the hardcore a bit
before I blind it with sand?!





Ideally you need a wacker to compact it. They are quite good fun to
use. Having said that, this is a very small section of floor, and I
suspect a good bit of jumping up and down might be enough.

The reason for doing this is that if you don't compact it
sufficiently, there's a chance of future settlement, which could cause
your 1x1.7m slab to move relative to its surroundings.



I have a similar question to the OP

I want to put an 8 by 12 foot shed on an old greenhouse base. I intend
throwing all the various bricks and rubble in the middle and topping it
off with hard core.

Without tamping it down, will I have any serious settlement problems?


No. I'd mix in some sand and gravel as well though, so its fairly solid
and there aren't any air pockets.

I threw down a load of MOT type one crush'n'go stuff, and where we havbe
driven cars over it it's now like solid concrete, but where we haven't,
it hasn't settlesd down much at all. Ive laid concrete and stoine over
bits of it no probs.

The whacker made eff all difference frankly. What really works is 30 ton
lorrys driving over it. THATS whacking!



Dave

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