When pouring mass concrete foundations, I have some questions:

1. What is the best way to make guides for the tamping down boards ?
(I'm sure I've seen wooden pegs sticking up at the required height -
if so, can these be left in place ?)

2. Since the concrete will be delivered quickly (a chute or pump), how
can you get just the right amount of concrete in to level to the
tamping boards ? Have an overflow pit ready just in case ?

3. What to do with excess concrete, since the lorry will want to empty
it's load ?

4. If it turns out I have ordered just short of the required amount
and the foundations are a little low, will this be rectifiable, or
will BCO go loopy and require it all the be dug up ! Would it be
reasonable to have tamping guides one 75mm lower just in case this
happens ?

TIA,
Simon.

sm_jamieson wrote:
When pouring mass concrete foundations, I have some questions:

1. What is the best way to make guides for the tamping down boards ?
(I'm sure I've seen wooden pegs sticking up at the required height -
if so, can these be left in place ?)

Yes.

2. Since the concrete will be delivered quickly (a chute or pump), how
can you get just the right amount of concrete in to level to the
tamping boards ? Have an overflow pit ready just in case ?


You can't. Its a bloody nightmare and you WON'T get it dead level.

That is what half bricks and a good bricklayer are for.

3. What to do with excess concrete, since the lorry will want to empty
it's load ?

Fill the thing up, and level it as best you can. Takes a lot of blokes
with rakes and so on. If its a bit higher so be it. The Earth is not
flat ether.


4. If it turns out I have ordered just short of the required amount
and the foundations are a little low, will this be rectifiable, or
will BCO go loopy and require it all the be dug up ! Would it be
reasonable to have tamping guides one 75mm lower just in case this
happens ?

Just don't tell him. or mix up a shade more. Or use conctre precast
blocks to make up the difference if you like., HE probably would not
mind that. Use a very strong mortar underground tho 2:1 sand:cement
IIRC. Others will know.

After the rigmarole of pouring mine, next time I will leave it all about
4-6" below and use blockwork to build up on a variable mortar bed. Its a
lot easier to lay blocks to a string than pour concrete to a level.


IIRC the issue with foundations going deep, is not so much that whats
higher up has to be strong, but that what's lower down rests on soil
that is more stable - i.e. into the area where soil huimidity is fairly
constant, and tree roots don't go..




TIA,
Simon.

Hire a concrete poker/vibrator. It makes levelling up to the
shuttering a great deal easier, as well as greatly reducing trapped
air and improving the resultant strength of the concrete.

On 19 Sep, 12:07, The Natural Philosopher wrote:
sm_jamieson wrote:
When pouring mass concrete foundations, I have some questions:

1. What is the best way to make guides for the tamping down boards ?
(I'm sure I've seen wooden pegs sticking up at the required height -
if so, can these be left in place ?)

Yes.



2. Since the concrete will be delivered quickly (a chute or pump), how
can you get just the right amount of concrete in to level to the
tamping boards ? Have an overflow pit ready just in case ?

You can't. Its a bloody nightmare and you WON'T get it dead level.

That is what half bricks and a good bricklayer are for.

3. What to do with excess concrete, since the lorry will want to empty
it's load ?

Fill the thing up, and level it as best you can. Takes a lot of blokes
with rakes and so on. If its a bit higher so be it. The Earth is not
flat ether.

4. If it turns out I have ordered just short of the required amount
and the foundations are a little low, will this be rectifiable, or
will BCO go loopy and require it all the be dug up ! Would it be
reasonable to have tamping guides one 75mm lower just in case this
happens ?

Just don't tell him. or mix up a shade more. Or use conctre precast
blocks to make up the difference if you like., HE probably would not
mind that. Use a very strong mortar underground tho 2:1 sand:cement
IIRC. Others will know.

After the rigmarole of pouring mine, next time I will leave it all about
4-6" below and use blockwork to build up on a variable mortar bed. Its a
lot easier to lay blocks to a string than pour concrete to a level.

Well the plans have 3 brick courses / 1 block between the foundation
and ground level, and I'm sure it's better to have it too low rather
than too high, since fiddling with part-blocks would be a pain
(although thermalite easy to cut !).
Probabaly aim for a point a bit lower, then "top up" !

Cheers,
Simon.

wrote:
Hire a concrete poker/vibrator. It makes levelling up to the
shuttering a great deal easier, as well as greatly reducing trapped
air and improving the resultant strength of the concrete.

Wish I'd known that..

sm_jamieson wrote:
On 19 Sep, 12:07, The Natural Philosopher wrote:
sm_jamieson wrote:
When pouring mass concrete foundations, I have some questions:
1. What is the best way to make guides for the tamping down boards ?
(I'm sure I've seen wooden pegs sticking up at the required height -
if so, can these be left in place ?)
Yes.



2. Since the concrete will be delivered quickly (a chute or pump), how
can you get just the right amount of concrete in to level to the
tamping boards ? Have an overflow pit ready just in case ?
You can't. Its a bloody nightmare and you WON'T get it dead level.

That is what half bricks and a good bricklayer are for.

3. What to do with excess concrete, since the lorry will want to empty
it's load ?
Fill the thing up, and level it as best you can. Takes a lot of blokes
with rakes and so on. If its a bit higher so be it. The Earth is not
flat ether.

4. If it turns out I have ordered just short of the required amount
and the foundations are a little low, will this be rectifiable, or
will BCO go loopy and require it all the be dug up ! Would it be
reasonable to have tamping guides one 75mm lower just in case this
happens ?
Just don't tell him. or mix up a shade more. Or use conctre precast
blocks to make up the difference if you like., HE probably would not
mind that. Use a very strong mortar underground tho 2:1 sand:cement
IIRC. Others will know.

After the rigmarole of pouring mine, next time I will leave it all about
4-6" below and use blockwork to build up on a variable mortar bed. Its a
lot easier to lay blocks to a string than pour concrete to a level.

Well the plans have 3 brick courses / 1 block between the foundation
and ground level, and I'm sure it's better to have it too low rather
than too high, since fiddling with part-blocks would be a pain
(although thermalite easy to cut !).
Probabaly aim for a point a bit lower, then "top up" !


Actually mine came out a bit high, but as my ground man said 'its always
easier to add hardcore and soil to get the ground level up, than dig
trenches to drain a house where the soil is higher than the DPC".

Being on a slight slope, we ended up using a lot of old foundations to
fill in a 2ft deep terrace and I built a haha as well, which makes a
nice microclimate for Mediterranean plants, that don't mind all the
buried builders sand etc..

MY BCO was concerned to get the foundations below tree root level: How
high they went post that wasn't really an issue..the next issue was that
the DPC was above soil final level by two bricks or so.

Having the house high also makes drain building easier. Both foul and
rainwater.

Be sure to get these in next. BEFORE you start laying the blocks. Many
of them will have to run THROUGH that. Use lintels over, and gravel
backfill..



Cheers,
Simon.

On 19 Sep, 13:03, The Natural Philosopher wrote:
wrote:
Hire a concrete poker/vibrator. It makes levelling up to the
shuttering a great deal easier, as well as greatly reducing trapped
air and improving the resultant strength of the concrete.

Wish I'd known that..

Why, what's the story ?
Did your foundations fail, or was it just very un-level ?
Or worse ?
On another thread it said just get the driver to wet the concrete a
bit so that it flows easily. Since mine may have to be pumped, I guess
it will be well plasticized anyway.
Simon.

On 19 Sep, 13:09, The Natural Philosopher wrote:
sm_jamieson wrote:
On 19 Sep, 12:07, The Natural Philosopher wrote:
sm_jamieson wrote:
When pouring mass concrete foundations, I have some questions:
1. What is the best way to make guides for the tamping down boards ?
(I'm sure I've seen wooden pegs sticking up at the required height -
if so, can these be left in place ?)
Yes.

2. Since the concrete will be delivered quickly (a chute or pump), how
can you get just the right amount of concrete in to level to the
tamping boards ? Have an overflow pit ready just in case ?
You can't. Its a bloody nightmare and you WON'T get it dead level.

That is what half bricks and a good bricklayer are for.

3. What to do with excess concrete, since the lorry will want to empty
it's load ?
Fill the thing up, and level it as best you can. Takes a lot of blokes
with rakes and so on. If its a bit higher so be it. The Earth is not
flat ether.

4. If it turns out I have ordered just short of the required amount
and the foundations are a little low, will this be rectifiable, or
will BCO go loopy and require it all the be dug up ! Would it be
reasonable to have tamping guides one 75mm lower just in case this
happens ?
Just don't tell him. or mix up a shade more. Or use conctre precast
blocks to make up the difference if you like., HE probably would not
mind that. Use a very strong mortar underground tho 2:1 sand:cement
IIRC. Others will know.

After the rigmarole of pouring mine, next time I will leave it all about
4-6" below and use blockwork to build up on a variable mortar bed. Its a
lot easier to lay blocks to a string than pour concrete to a level.

Well the plans have 3 brick courses / 1 block between the foundation
and ground level, and I'm sure it's better to have it too low rather
than too high, since fiddling with part-blocks would be a pain
(although thermalite easy to cut !).
Probabaly aim for a point a bit lower, then "top up" !

Actually mine came out a bit high, but as my ground man said 'its always
easier to add hardcore and soil to get the ground level up, than dig
trenches to drain a house where the soil is higher than the DPC".

My final floor level is fixed, since it's an extension. And the
original 1930s house only has 1 brick level between ground and DPC, so
I will have to reduce ground level around the extension to make the
floors line up and have 2 bricks clear.


Being on a slight slope, we ended up using a lot of old foundations to
fill in a 2ft deep terrace and I built a haha as well, which makes a
nice microclimate for Mediterranean plants, that don't mind all the
buried builders sand etc..

MY BCO was concerned to get the foundations below tree root level: How
high they went post that wasn't really an issue..the next issue was that
the DPC was above soil final level by two bricks or so.

Having the house high also makes drain building easier. Both foul and
rainwater.

It seems that drain gullies etc are sized to sit on top of the
sticking out bit of the concrete footings, and meet ground at about 3
brick courses. Drain levels roughly fixed as existing. If BCO agrees,
I will pour foundations around the existing clay drains (leaving 150mm
around IIRC), and sort out the new plastic connecting drains just
before the floor slab is done. The bit that will remain clay goes into
a public sewer, and I shan't be touching that !


Be sure to get these in next. BEFORE you start laying the blocks. Many
of them will have to run THROUGH that. Use lintels over, and gravel
backfill..

Cheers,
Simon.

"sm_jamieson" wrote in message
ups.com...


SNIP


Well the plans have 3 brick courses / 1 block between the foundation
and ground level, and I'm sure it's better to have it too low rather
than too high, since fiddling with part-blocks would be a pain
(although thermalite easy to cut !).
Probabaly aim for a point a bit lower, then "top up" !

Cheers,
Simon.


I wouldn't want thermalites below dpc level - far too porous - first
freeze will blow them away

AWEM

On 19 Sep, 14:08, "Andrew Mawson"
wrote:
"sm_jamieson" wrote in message

ups.com...

SNIP
Well the plans have 3 brick courses / 1 block between the foundation
and ground level, and I'm sure it's better to have it too low rather
than too high, since fiddling with part-blocks would be a pain
(although thermalite easy to cut !).
Probabaly aim for a point a bit lower, then "top up" !

Cheers,
Simon.

I wouldn't want thermalites below dpc level - far too porous - first
freeze will blow them away

AWEM

If that is the case, their must be a reg about it. I will ask BCO.
I wouldn't want them at all !
It was never specified on the plans to use different below DPC. Since
perimeter insulation comes up to DPC level, no reason not to use
concrete blocks or just bricks. Another BCO question.
Simon.

When I worked on site (Henges & Pyramids Ltd), concrete pokers were
standard practice on all pours. I believe there are low viscosity
mixes now that are meant to be self levelling - but cement
manufacturers still seem to recommend pokering on standard mixes.

HSS do a nice small electric unit I've used on footings:
http://www.hss.com/g/46545/Poker-Vib...tric-39mm.html

On Wed, 19 Sep 2007 06:26:45 -0700, a particular chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:

On 19 Sep, 14:08, "Andrew Mawson"
wrote:

I wouldn't want thermalites below dpc level - far too porous - first
freeze will blow them away

If that is the case, their must be a reg about it. I will ask BCO.
I wouldn't want them at all !

Have a look at the manufacturer's details for the particular block,
but AFAIK, most can be used below DPC. Indeed, Celcon & Thermalite
make trenchblocks specifically for foundations.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

On Wed, 19 Sep 2007 03:02:01 -0700, a particular chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:

4. If it turns out I have ordered just short of the required amount
and the foundations are a little low, will this be rectifiable, or
will BCO go loopy and require it all the be dug up !

Depends how low. Assuming standard unreinforced strip footings, then
provided the thickness of the concrete is no less than its spread. If
you have 600mm wide footings, they'll have 150mm spread, so your
foundations would need to be at least 150mm thick.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

On 19 Sep, 18:51, Hugo Nebula abuse@localhost wrote:
On Wed, 19 Sep 2007 03:02:01 -0700, a particular chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:

4. If it turns out I have ordered just short of the required amount
and the foundations are a little low, will this be rectifiable, or
will BCO go loopy and require it all the be dug up !

Depends how low. Assuming standard unreinforced strip footings, then
provided the thickness of the concrete is no less than its spread. If
you have 600mm wide footings, they'll have 150mm spread, so your
foundations would need to be at least 150mm thick.
--

No problems here - they are mass concrete trench between 750 and
1000mm thick !
Simon.

sm_jamieson wrote:
On 19 Sep, 13:03, The Natural Philosopher wrote:
wrote:
Hire a concrete poker/vibrator. It makes levelling up to the
shuttering a great deal easier, as well as greatly reducing trapped
air and improving the resultant strength of the concrete.
Wish I'd known that..

Why, what's the story ?
Did your foundations fail, or was it just very un-level ?

pretty unlevel. Needd as much as a full brick at ne end, and saller
chinks n between. The brickie cursed.

Or worse ?
On another thread it said just get the driver to wet the concrete a
bit so that it flows easily.

Tried that. It was a BIG three lorry set of foundations tho.

Since mine may have to be pumped, I guess
it will be well plasticized anyway.

Still doesn;t help. You need a vibrator..
Simon.

it will be well plasticized anyway.

Still doesn;t help. You need a vibrator..

Just found a link to use in another reply - I'd recommend Lafarge's
concrete application guide http://www.lafargecement.co.uk/

Look under "applications-concrete", then on the next page half way
down click on the link for the pdf of a leaflet - excellent advice in
the second half of the leaflet. Strongly recommends pokering.

On 20 Sep, 08:50, " wrote:
it will be well plasticized anyway.



Still doesn;t help. You need a vibrator..

Just found a link to use in another reply - I'd recommend Lafarge's
concrete application guidehttp://www.lafargecement.co.uk/

Look under "applications-concrete", then on the next page half way
down click on the link for the pdf of a leaflet - excellent advice in
the second half of the leaflet. Strongly recommends pokering.

Well hiring a poker is not expensive, so why not ?
Cheers,
Simon.

On 20 Sep, 11:34, sm_jamieson wrote:
On 20 Sep, 08:50, " wrote:

it will be well plasticized anyway.

Still doesn;t help. You need a vibrator..

Just found a link to use in another reply - I'd recommend Lafarge's
concrete application guidehttp://www.lafargecement.co.uk/

Look under "applications-concrete", then on the next page half way
down click on the link for the pdf of a leaflet - excellent advice in
the second half of the leaflet. Strongly recommends pokering.

Well hiring a poker is not expensive, so why not ?
Cheers,
Simon.

I've been reading a bit on the use of these vibrating pokers.
Sounds like if you vibrate for too long, you can do irreversable
damage, by causing the aggregate sizes to separate out, and you should
be very careful how they are used, lowering under own weight, not
dragging sideways etc.
I wonder how often they are actually used on domestic pours.
I bet not much.
Anyone know about this ?
Simon.

On Thu, 20 Sep 2007 03:59:19 -0700, a particular chimpanzee,
sm_jamieson randomly hit the keyboard and
produced:

I've been reading a bit on the use of these vibrating pokers.
Sounds like if you vibrate for too long, you can do irreversable
damage, by causing the aggregate sizes to separate out, and you should
be very careful how they are used, lowering under own weight, not
dragging sideways etc.
I wonder how often they are actually used on domestic pours.
I bet not much.

Even less.

If it's ready-mix, it's already the right consistency. If you're
mixing your own, you shouldn't rely on the poker to mix it in-situ.
Pokering is really only needed to make sure the concrete gets into all
the hollows around formwork and reinforcement.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

Pokering is really only needed to make sure the concrete gets into all
the hollows around formwork and reinforcement.

And to remove air inclusions from mixing, transportation & pouring.
Check out that Lafarge link.