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Cutting concrete blocks



 
 
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  #1  
Old February 27th 10, 03:08 PM posted to uk.d-i-y
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Posts: 293
Default Cutting concrete blocks

Getting closer to wall building time now the weather has warmed up a bit; if
only it would stop raining!

I will obviously need to cut concrete blocks - I will be using the 'medium
density' blocks for external walls with no rendering.
[At least I think the normal ones are described as 'medium density' - it
does beg the question as to what 'dense' blocks are.]

I see there are some hand saws to cut blocks although most (but not all) of
them say they are for lightweight blocks.
I have some difficulty visualising cutting the 'medium density' concrete
blocks with a hand saw.
Is this practical?

Using Google I have seen various descriptions of block cutting methods.
Scoring with a cold chisel all round the block seems to be a very slow way.
Is scoring all the way round with a small angle grinder a good way to
prepare blocks for cutting?

The alternative seems to be the huge and nasty looking stone cutters you see
builders using.
These look expensive and potentially dangerous.
Are these necessary or are there better ways?

I intend to use stretcher bond to build single block walls but will
obviously have to cut blocks to fit in doors and windows and also where the
wall length is not divisible by the block length.

TIA

Dave R

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  #2  
Old February 27th 10, 03:14 PM posted to uk.d-i-y
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Posts: 3,574
Default Cutting concrete blocks

On Feb 27, 2:08*pm, "David WE Roberts" wrote:


I see there are some hand saws to cut blocks although most (but not all) of
them say they are for lightweight blocks.
I have some difficulty visualising cutting the 'medium density' concrete
blocks with a hand saw.
Is this practical?


not a hope in hell. Use an angle grinder.


NT
  #3  
Old February 27th 10, 03:18 PM posted to uk.d-i-y
external usenet poster
 
Posts: 293
Default Cutting concrete blocks


"David WE Roberts" wrote in message
...
Getting closer to wall building time now the weather has warmed up a bit;
if only it would stop raining!

I will obviously need to cut concrete blocks - I will be using the 'medium
density' blocks for external walls with no rendering.
[At least I think the normal ones are described as 'medium density' - it
does beg the question as to what 'dense' blocks are.]

snip

Any idea how much to allow for wastage?
I am not the best cutter of bricks etc.

  #4  
Old February 27th 10, 03:25 PM posted to uk.d-i-y
external usenet poster
 
Posts: 18,600
Default Cutting concrete blocks

David WE Roberts wrote:
Getting closer to wall building time now the weather has warmed up a
bit; if only it would stop raining!

I will obviously need to cut concrete blocks - I will be using the
'medium density' blocks for external walls with no rendering.
[At least I think the normal ones are described as 'medium density' - it
does beg the question as to what 'dense' blocks are.]

I see there are some hand saws to cut blocks although most (but not all)
of them say they are for lightweight blocks.
I have some difficulty visualising cutting the 'medium density' concrete
blocks with a hand saw.
Is this practical?

Using Google I have seen various descriptions of block cutting methods.
Scoring with a cold chisel all round the block seems to be a very slow way.
Is scoring all the way round with a small angle grinder a good way to
prepare blocks for cutting?


I just use a bolster and a club hammer.

If I want a pretty result, I don't use concrete blocks ;-)

  #5  
Old February 27th 10, 03:30 PM posted to uk.d-i-y
external usenet poster
 
Posts: 183
Default Cutting concrete blocks

David WE Roberts wrote:
Getting closer to wall building time now the weather has warmed up a
bit; if only it would stop raining!

I will obviously need to cut concrete blocks - I will be using the
'medium density' blocks for external walls with no rendering.
[At least I think the normal ones are described as 'medium density' -
it does beg the question as to what 'dense' blocks are.]


medium density aren't packed as tightly in the mould as dense blocks
are....I think they just use a dry mix and don't pack it down, wheras a
dense block is mixed wet and then vibrated during manufacture to expel air
and to strengthen the blocks


I see there are some hand saws to cut blocks although most (but not
all) of them say they are for lightweight blocks.
I have some difficulty visualising cutting the 'medium density'
concrete blocks with a hand saw.
Is this practical?


you can't cut concrete blocks with any kind of handsaw, these are for the
'thermalite' type of blocks


Using Google I have seen various descriptions of block cutting
methods. Scoring with a cold chisel all round the block seems to be a
very slow way. Is scoring all the way round with a small angle
grinder a good way to prepare blocks for cutting?


they can be cut with a bolster chisel but as you say it's time consuming and
not very accurate


The alternative seems to be the huge and nasty looking stone cutters
you see builders using.
These look expensive and potentially dangerous.
Are these necessary or are there better ways?


9 inch diamond disc in large angle grinder, failing that, a small disc in a
small grinder will cut an inch into it all the way around and then a few
taps with aforementioned bolster will snap it off - the cut isn't clean, but
it is at the edges and this is what will be visible IYSWIM


I intend to use stretcher bond to build single block walls but will
obviously have to cut blocks to fit in doors and windows and also
where the wall length is not divisible by the block length.


You make the wall length to suit full blocks :-P take a block and use it as
a measure, starting at one corner and marking a scratch on the concrete
where it ends, then move it along, leaving an inch (or just less) for the
joint and make another scratch, continue until you reach the opposite
corner - if it works out that you have an odd size left, of say, 6 inches,
start your building 3 inches in from where you began, meaning you will have
3 inches of concrete showing at each end.
It's entirely up to you of course, but I think pieces in a wall (which will
be all the way up to the top) looks hideous, and it is going to be on show.
If you are ordering the windows and doors afterwards, build the openings
block sized, that is to say you have full and half blocks up each side of
the openings, rather than 2 inch pieces on one side and 4 inch peices on the
other. It's more economical because obviously you get two usuable pieces
with each cut and it looks better, but if yuou already have the windows etc,
then you have to build the openings to suit them.,

--
Phil L
RSRL Tipster Of The Year 2008


  #6  
Old February 27th 10, 03:35 PM posted to uk.d-i-y
external usenet poster
 
Posts: 183
Default Cutting concrete blocks

David WE Roberts wrote:
"David WE Roberts" wrote in message
...
Getting closer to wall building time now the weather has warmed up a
bit; if only it would stop raining!

I will obviously need to cut concrete blocks - I will be using the
'medium density' blocks for external walls with no rendering.
[At least I think the normal ones are described as 'medium density'
- it does beg the question as to what 'dense' blocks are.]

snip

Any idea how much to allow for wastage?
I am not the best cutter of bricks etc.


I'd order what I needed to be delivered, and then pick up a dozen or so at a
time if any extras are required, you are better under ordering with blocks.

Also forgot to ask, are you intending adding any butresses? - if the wall is
longer than 4m, you'll need a buttress in the middle, basically just a stack
of blocks, tied into the main wall with tie wires on every course

--
Phil L
RSRL Tipster Of The Year 2008


  #7  
Old February 27th 10, 04:26 PM posted to uk.d-i-y
external usenet poster
 
Posts: 1,051
Default Cutting concrete blocks

David WE Roberts wrote:
Getting closer to wall building time now the weather has warmed up a
bit; if only it would stop raining!

I will obviously need to cut concrete blocks - I will be using the
'medium density' blocks for external walls with no rendering.
[At least I think the normal ones are described as 'medium density' - it
does beg the question as to what 'dense' blocks are.]

I see there are some hand saws to cut blocks although most (but not all)
of them say they are for lightweight blocks.
I have some difficulty visualising cutting the 'medium density' concrete
blocks with a hand saw.
Is this practical?

Using Google I have seen various descriptions of block cutting methods.
Scoring with a cold chisel all round the block seems to be a very slow way.
Is scoring all the way round with a small angle grinder a good way to
prepare blocks for cutting?

The alternative seems to be the huge and nasty looking stone cutters you
see builders using.
These look expensive and potentially dangerous.
Are these necessary or are there better ways?

I intend to use stretcher bond to build single block walls but will
obviously have to cut blocks to fit in doors and windows and also where
the wall length is not divisible by the block length.

TIA

Dave R

use an angle grinder with a diamond blade, they are cheap as chips now

  #8  
Old February 27th 10, 04:34 PM posted to uk.d-i-y
external usenet poster
 
Posts: 293
Default Cutting concrete blocks


"Phil L" wrote in message
om...
David WE Roberts wrote:
"David WE Roberts" wrote in message
...
Getting closer to wall building time now the weather has warmed up a
bit; if only it would stop raining!

I will obviously need to cut concrete blocks - I will be using the
'medium density' blocks for external walls with no rendering.
[At least I think the normal ones are described as 'medium density'
- it does beg the question as to what 'dense' blocks are.]

snip

Any idea how much to allow for wastage?
I am not the best cutter of bricks etc.


I'd order what I needed to be delivered, and then pick up a dozen or so at
a time if any extras are required, you are better under ordering with
blocks.

Also forgot to ask, are you intending adding any butresses? - if the wall
is longer than 4m, you'll need a buttress in the middle, basically just a
stack of blocks, tied into the main wall with tie wires on every course


I will need to add something in the middle of the back wall as it is 7.8m
long.
The front wall will also need some extra support and I am contemplating how
to work this in around windows, doors, and a place for the stove.
On the front wall this may end up as a fireplace for the stove to provide
sides for protection from the hot metal.

I have more or less decided to go for the maximum length of block wall and
ignore the fact that part blocks look less pretty.
For three sides this is not an issue as they are facing a fence.
The only visible area is the front and the doors are going to make a
difference to the number of blocks.

I can always hide stuff behind plant etc, or perhaps render the front wall.

Mainly, I don't mind if it is ugly as long as it is up!
[As the actress said to the bishop]

I would like to be able to get concrete blocks at less than 1 per block
because I need at least 330 blocks to do the back and sides.

Cheers

Dave R

  #9  
Old February 27th 10, 05:24 PM posted to uk.d-i-y
external usenet poster
 
Posts: 672
Default Cutting concrete blocks

David WE Roberts wrote:

The alternative seems to be the huge and nasty looking stone cutters you
see builders using.
These look expensive and potentially dangerous.


Correct, but there are disadvantages as well



  #10  
Old February 27th 10, 05:31 PM posted to uk.d-i-y
external usenet poster
 
Posts: 744
Default Cutting concrete blocks

On Feb 27, 3:34 pm, "David WE Roberts" wrote:
"Phil L" wrote in message

om...



David WE Roberts wrote:
"David WE Roberts" wrote in message
...
Getting closer to wall building time now the weather has warmed up a
bit; if only it would stop raining!


I will obviously need to cut concrete blocks - I will be using the
'medium density' blocks for external walls with no rendering.
[At least I think the normal ones are described as 'medium density'
- it does beg the question as to what 'dense' blocks are.]
snip


Any idea how much to allow for wastage?
I am not the best cutter of bricks etc.


I'd order what I needed to be delivered, and then pick up a dozen or so at
a time if any extras are required, you are better under ordering with
blocks.


Also forgot to ask, are you intending adding any butresses? - if the wall
is longer than 4m, you'll need a buttress in the middle, basically just a
stack of blocks, tied into the main wall with tie wires on every course


I will need to add something in the middle of the back wall as it is 7.8m
long.
The front wall will also need some extra support and I am contemplating how
to work this in around windows, doors, and a place for the stove.
On the front wall this may end up as a fireplace for the stove to provide
sides for protection from the hot metal.


I'd be wary of enclosing your stove too tightly (if at all) as it'll
stifle it and take longer and use more fuel to heat the space up.
Could you praps place it in a corner and let it convect and radiate
out from there without being "boxed in"?

Cheers
JimK
 




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