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