Large cracks appearing in walls.


P

Peter Jason

I have a 100-year old terrace house which has just had the ground floor
overhauled.

This involved:
1/ Old ground floor system removed
2/ 3" of soil removed throught.
3/ Ventilation holes in all underfloor walls.
4/ Large ventilation holes in ouside walls connecting to the underfloor
space.
5/ New stumps & structure.
6/ New pine floor for ground floor.
7/ Central heating pipework (hydronic.)
8/ All stormwater drainage replaced.
9/ All areas around the house sealed with concrete/pavers.

Would any of the above be causing the cracks to form, and is the house
merely settling to the new conditions?

Will the cracking stop after a while, and if not what can be done?

Please help, Peter.
 
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R

RicodJour

Peter said:
I have a 100-year old terrace house which has just had the ground floor
overhauled.

This involved:
1/ Old ground floor system removed
2/ 3" of soil removed throught.
3/ Ventilation holes in all underfloor walls.
4/ Large ventilation holes in ouside walls connecting to the underfloor
space.
5/ New stumps & structure.
6/ New pine floor for ground floor.
7/ Central heating pipework (hydronic.)
8/ All stormwater drainage replaced.
9/ All areas around the house sealed with concrete/pavers.

Would any of the above be causing the cracks to form, and is the house
merely settling to the new conditions?

Will the cracking stop after a while, and if not what can be done?

Please help, Peter.
Fine job on listing the work, but tell us more aobut the cracks. Size,
location, growing? That sort of thing.

R
 
P

Peter Jason

OK, more detail.

The house is two story, and solid brick & render.

When purchased, the house had some water damage due to falling and lateral
damp, and would receive storm water from the neighbours down-pipes (we added
blue dye to his guttering and the area under the house turned blue).

Thus the underfloor space was damp and sometimes wet, and had been so for
many years. Still there were only very few wall cracks at this stage.

We stopped all water getting under the house and then proceeded to repair
all past damage.

Ground floor only:

1/ We tore up and discarded the whole ground floor timber, so exposing the
earth beneath. This was in such a bad smelly condition that about a depth
of 3" 6" was scraped up and discarded and this had the effect of increasing
the future underfloor space.

2/ While in this state we inspected the underfloor ventilation properties of
the underground floor space and found this to be very poor indeed.
Accordingly we opened holes in all the brick underfloor walls to improve
cross-flow ventilation between the rooms, and also opened (drilled) further
4" dia openings connecting the underfloor to the outside. The back part of
the house is about 4" below ground level so we made a step in a rear
above-floor alcove and used this to connect the underfloor to the outside.

3/ While the floor was up we had all the salt-encrusted rising damp removed
and re-rendered and a new dampcourse installed. Also the plumbing for the
hydronic central heating was laid.

4/ Then a new floor was installed, with concrete stumps etc.

About 2 years after all this, cracking started to appear in both upstairs
and downstairs rooms and has become steadily worse, from hairline cracks to
some now about 1/8" wide. Additionally some of the plaster (lath) ceilings
downstairs are buckling, cracking and dropping paint flecks.

These cracks are all aligned at about 45degrees approx and some can be seen
on the exterior walls too.

Why the cracks?

Have we drastically lowered the water table beneath the house (which sits on
clay soil) causing it to shrink and settle?

Is this a temporary "settling in" thing, and will the cracks will stop
increasing in size?

Please help, Peter
 
R

RicodJour

Peter said:
OK, more detail.

The house is two story, and solid brick & render.

When purchased, the house had some water damage due to falling and lateral
damp, and would receive storm water from the neighbours down-pipes (we added
blue dye to his guttering and the area under the house turned blue).

Thus the underfloor space was damp and sometimes wet, and had been so for
many years. Still there were only very few wall cracks at this stage.

We stopped all water getting under the house and then proceeded to repair
all past damage.

Ground floor only:

1/ We tore up and discarded the whole ground floor timber, so exposing the
earth beneath. This was in such a bad smelly condition that about a depth
of 3" 6" was scraped up and discarded and this had the effect of increasing
the future underfloor space.

2/ While in this state we inspected the underfloor ventilation properties of
the underground floor space and found this to be very poor indeed.
Accordingly we opened holes in all the brick underfloor walls to improve
cross-flow ventilation between the rooms, and also opened (drilled) further
4" dia openings connecting the underfloor to the outside. The back part of
the house is about 4" below ground level so we made a step in a rear
above-floor alcove and used this to connect the underfloor to the outside.

3/ While the floor was up we had all the salt-encrusted rising damp removed
and re-rendered and a new dampcourse installed. Also the plumbing for the
hydronic central heating was laid.

4/ Then a new floor was installed, with concrete stumps etc.

About 2 years after all this, cracking started to appear in both upstairs
and downstairs rooms and has become steadily worse, from hairline cracks to
some now about 1/8" wide. Additionally some of the plaster (lath) ceilings
downstairs are buckling, cracking and dropping paint flecks.

These cracks are all aligned at about 45degrees approx and some can be seen
on the exterior walls too.

Why the cracks?

Have we drastically lowered the water table beneath the house (which sits on
clay soil) causing it to shrink and settle?
When you first mentioned the wet basement and the neighbors gutters, I
immediately thought of clay subsoil drying and shrinking. I'm glad you
had that information at hand, because it is almost assuredly what you
are experiencing.
Is this a temporary "settling in" thing, and will the cracks will stop
increasing in size?
Clay is fickle stuff. I am not a geotechnical engineer, and even
geotechnical engineers get fits when dealing with clay. I can't say
for sure whether it will keep going or not, but I would hazard a guess
that it will slow down and stop...eventually. The question is, do you
standby and watch your building deteriorate while you are waiting?
Probably not a good idea.

On this side of the drink (please use whatever translation services
necessary so the terminology doesn't hang you up), there are companies
that specialize in reinforcing foundations using different techniques.
One technique involves injecting grout under the existing foundation,
called mudjacking, and another uses helical screw anchors driven in
next to the foundation and attached to the existing. Only someone
familiar with your soil conditions and the involved costs can help
steer you in the right direction. Call an engineer with experience in
soils and foundation repair to come take a look and design a solution
for you.

R
 
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C

chickenwing

Peter said:
Why the cracks?

yeah, you fornicated with the footings and what not...
dirt in and out...

concrete piers...jacks...

sounds like maj surgery, I would expect some stress cracks

when it rains, you take on the surge, so I don't know what can be done
about this

** maybe put some sort of caliper on a crack, see how much its moving
 
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