Inner Skin Cracked Only

[i_am_fubar]

We had a crack on the wall, stripped off some of the 2 layers of plaster, layer of textured paint and the render around it and found awful blockwork. 2" 'mortar' gaps in places. The mortar feeling like it's a 10:1 or worse mix:

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• i_am_fubar
• 30 Aug 2013
• 1

So, fearing subsidence, we've dug down to the foundations and can confirm they exist:, although a bit shoddy in the corner. More digging needed.

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• i_am_fubar
• 30 Aug 2013
• 1

Removed the loose blocks from around the crack (mainly just pulling them out the wall):

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• i_am_fubar
• 30 Aug 2013
• 1

There was some re-pointing on the outside of the house we thought may have been hiding the crack in the outer skin, but looking at the back of it (through the new hole), the block work, while a little poor, is sound.

So, we have a large crack in the inner skin and a number of loose blocks, But a sound outer skin. The only outer skin damage we can see is right in the corner, just above the DPC.

Also, all the wall ties seem to be loose in the outer skin where we've taken the blocks out AND they all slope down toward the inner skin

Plan at the moment is to...

1) resin some rebar into the existing foundations and back fill the hole with fresh concrete to reinforce the foundations.

2) Resin the wallties back in place and bend them to provide a proper slope away from the inner skin.

3) Re-build the inner wall with lightweight concrete blocks.

Anyone have any idea what could cause this? Current thoughts are:
a) Thick, poor mix mortar bed between foundations and block work that has crumbled.
b) Heavy impact from inside the house (punch bag stand, amateur wrestling gym... etc)

Cheers,
Fubar.

 

[Skimmers]

heli fix bars and resin stitch the cracks then sort out hangers

 

[i_am_fubar]

Not much of a crack left now. As I'm building the wall up, I'm thinking I may bed a strip of perforated stainless into the mortar as I lay the first blocks.

I would go helifix, but as I placed an order to twistfix 2 days ago and don't really want to pay more carriage.

However, the crack isn't the problem and I don't want to hide it with a remedial fix. Whatever caused it, caused it for a reason and I want to know what that is.

Fubar.

 

[^woody^]

Subsidence cracks go right through a double skin wall, not just one skin.

That crack was probably shrinkage

 

[i_am_fubar]

Cheers Woody,

The quality of mortar would definitely explain how shrinkage could be that bad. Will block it back up with some proper 1:5 mortar and see how she fairs... Also addressing the tie issue :/

Fubar.

 

[^woody^]

Weaker mortar is what is needed to prevent shrinkage cracking. But it probably wont matter now for this repair

 

[i_am_fubar]

There's weak mortar..... And there's compacted sand. We currently have the latter. Would it be worth going a bit weaker than 1:5?

Fubar.

 

[Skimmers]

put a wall plate in to carry the joists.
you can tie the block work to the face work wth twist fix or such like.

5/1 pug mix with a dash of feb dont over mix it it the mixer.
use H+H or celcon blocks
good solid beds nice well jointed perps and really run in with a pointing iron.

If your planing to leave some of the old cracked wall ten helifix the cracks then run off that wet the old surface before laying blocks