House construction - why single course of blocks?

[OldieNewbie]

Hi all,

 

In Ireland, in housing construction, why are some 4 inch blocks on the flat laid in single rows / courses and then other walls have double rows?

 

Thanks. 

[mike2016]

I can only think this is part of a cavity wall system? Maybe, outer brick is added later in the first case? Are the double rows side by side or with a gap? Might be for structural reasons? 

[Dave Jones]

block flat below DPC saves having to cavbity fill with conc.

[ProDave]

Pictures would help. but I think this is describing something I questioned.

 

Below ground wall build up was done as "block on flat" as above, no cavity.  I get that bit.  But the bricklayer laid a course of blocks on flat, then a second row of blocks of flat exactly on top of the first ones, i.e. no bond.  Then the next row was staggered creating a bond followed by another row exactly on top with no bond.  So in other words the blocks were staggered / bonded every other row.

 

Now I questioned this.  It would have been no more difficult to bond every single row of block on flat and surely that would have been stronger? so why did he not do that?  His reply was that is how he was taught to do it.

 

So it is a question for bricklayers please, why not bond every single row of block on flat?

 

EDIT here is a picture of what I am trying to describe, block on flat courses bonded every other row.

 

[Dave Jones]

couldn't get hold of trench blocks ?

 

its normal practice not to bond as the pic above below DPC, sleeper walls for b and b etc