Cracks in exterior walls - Information

[captain dandy]

Hi

I have noticed a couple of vertical cracks in the external walls of my house which seem to carry right through the masonry.

One by the front door has been there since we moved in about 15 years ago, but seems to have widened slightly. The other (which is causing the greatest concern) is under a ground floor window and runs to the floor. it's about four foot in length, and about 1-2mm wide. It seems to have opened up since i last inspected it a couple of years ago. I'm posting to find out if it's something I need to act on now or if simply filling it and re wallpapering the area will solve the problem.

the house is rendered externally, built of breeze block and is approximately 30 years old. There's no sign of bulging on either crack.

 

[^woody^]

Vertical or stepped? And on the inside wall in the same place?

 

[captain dandy]

Vertical, and the cracks are visible both inside and out

 

[^woody^]

Vertical cracking of equal width tends to be shrinkage related. Common on solid walls, less common but not impossible on cavity walls. Not a major concern, but will need dealing with (sealing) especially so with a rendered finish. Repairs can depend on the location of the crack within the elevation and assessment of possible further contraction, so would need assessment on site.

Uneven width cracks are a different cause, and may indicate on-going movement

 

[captain dandy]

Apart from the render (which, to be honest is getting a bit elderly on that side of the house and go do with a freshen-up), what kind of sealing would I need to carry out? just plaster or is there something I can insert into the crack to ensure wetaherproofing? would silicone work?