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Hi Westan…thanks for the welcome!
Hi Phil….in the old days (ie,before myy time..)cement was not used in a mortar mix,it was just a mix of sand and lime.This mix was much softer than present day mortars,so if you are buying second hand bricks that have not been cleaned,pray that they are covered with lime mortar and not cement.Volume builders usually pay bricklayers $X per 1000 bricks,with the bricky supplying cement and lime.So they often skimp on these to boost their profits.
Lime in modern mortar has 2 purposes.It makes the mix easier for the bricky to work,and it also gives the finished wall some joint flexibility without cracking.Some people think that adding alittle extra cement will make their wall stronger,but the increased bond with the bricks doesn’t allow for any flexibility ,and instead of getting cracks in mortar joints,bricks will carck,as Westan mentioned.
I am happy to answer any other building related matters!
Peter,that is not really correct.Cracks in a newish building may either be serious or minor.Cracks appearing in new brickwork may be due to failure of the footing,shrinkage of reactive soils during dry periods,inadequately filled joints when the wall was laid,poor mortar quality (dirty or wrong sand,poor mixing quantities of ingredients,absence of limil etc……) or the wall may even not be sitting directly on the footing (it happens!).Cracks in older brickwork could also be due to similar problems,or because the foundation under the footing has moved/subsided/swelled etc.Or it could even be that the building has suffered some mechanical damage such as being struck by the tow bar of a reversing vehicle.Cracks appearing in the interior of a solid brick house could be for the same reasons as above,or there may be an old window or door that has been bricked up and plastered over that was not properly tied in to the existing brickwork.
Cracks in plaster board could be from shrinkage of the frame as it dries,mechanical damage,poor work practice during installation,structural deficiencies in the framework,poor repair of previous damage,or even a lack of reinforcing during jointing.
The causes of cracking in building fabric can be many and varied,and each case should be looked at by a competent person,on a case by case basis.
