Vertical Crack in Single Leaf Block Wall (Garage)

[Gavin31]

Hi All,
I am studying Sustainable Building and Renewable Energy and have to complete a project on a building defect for my Building Pathology module.
I have chosen my own garage wall as the defect.The crack in question is almost perfectly vertical which has led me to question whether it is subsidence or not. The crack does not extend to the base of the wall and is far wider at the top than it is at the bottom.
Im really stumped by thisand would appreciate some advice from anybody more knowledgeable than i am.
Ive created an album with images of the defect.

Oh and please ignore the dodgy repair job...my father is not handy

Thanks in advance,
Gavin.

 

[luisdesign]

Narrow vertical cracks are most often caused by shrinkage or minor settlement. I would not think this is a narrow crack, this is a wide crack that looks to be about 5-10mm in places! (you can see daylight through it!).

An initial assumption of significant settlement problems would probably be quite warranted and would certainly require further evaluation.

What is more worrying than the vertical crack is what appears to be a horizontal crack that runs from the original pictured vertical crack all the way to the front of the garage to the second vertical crack.


You want to check to see if the cracks are still active or if they are static - if you fill it, does it open up again? You should begin carefully monitoring the cracks. The more information you can gather over a longer period, the better.

As always, the crack is the sympton and not the cause. For more clues as to what the cause is you need to look at the wider picture.

You want to know how new the garage is, assess the position and location of the garage (ie; on the ridge of a hill or near a source of constant vibrations) and whether there has been any recent building works or burst drains nearby as well, of course, as the soil conditions. This would include whether or not any trees have recently been added or removed.

Hopefully that is enough to get you started!

 

[^woody^]

Tell you what, you consider the several possibilities based on construction and use and any nearby drains and trees, and then say which you think is the most likely cause, and then I'll comment on that.

That way you will learn the diagnosis process

 

[Gavin31]

Thanks very much for your help gents.

We have occupied the house for 30 years and the cracks definitely have not widened in that period. Which leads me to believe it was settlement of some sort.

My own thinking is that the ground was not compacted correctly or an inadequate foundation/ s&c screed was put down.

There was previously a tree on my neighbours property whose roots did cause damage to the pathway in between the houses, just beside the garage wall where the cracks are. However, while the roots did crack and lift the path it doesnt reach the point where the vertical crack is.

The house is on a hill, our driveway is at an angle of 30/35 degrees.

As far as use goes, the garage is not wide enough for a car so has always been used for storage, also out central heating boiler is located there, but i doubt it would have caused thermal movement.

As far as i can tell, the horizontal cracks are parallel to the ground level inside the garage, theres a step down to where i took those pictures from, so the ground level inside and outside the garage are different.

Ill take another couple of pictures soon as i can, showing the hill and differing ground levels.

Thanks again.

 

[Gavin31]

Oh and apart from cosmetic changes (windows etc) both our house and the neighbouring house remain unchanged since construction in the 1960's. There havent been any ground works that would have caused vibration or anything like that.

As far as drains go, we have never had an issue, once in my lifetime the sewage drains came close to overflowing but that was caused by an issue in a house 8 doors up and was rectified immediately when discovered.

Our gardens have never been waterlogged nor has there ever been ponding of any sort.

 

[Alastairreid]

My own thinking is that the ground was not compacted correctly or an inadequate foundation/ s&c screed was put down

That would be your best bet.

 

[Gavin31]

Seemis i was wrong about the horizontal cracks being parallel with the inside ground level, its actually higher than that.

the horizontal crack doesnt affect the blockwork, appears to just be on the outside render, inside the garage theres no sign of it.

Ill add another couple of pictures now, hopefully theyll help.

 

[jeds]

Gavin, the photos aren't very helpful. We need photos that show context. Starting from the bottom up the first possibility is failure of the ground. That might be to do with the original condition of the ground (compaction, sulfate etc) or it might be due to external influence. (drains, frost, slip, etc) Secondly, it might be due to failure of the foundation fabric. That might be due to poor fabric, poor design, poor workmanship, etc. You also need to rule out other possibilities; design and materials of walls, possible stress from roof.

It's possible you might not be able to determine the cause for sure without destructive investigation. That would mean breaking or core drilling the floor or digging around the outside. You obviously won't want to be doing that but you should still write up what options would be open to you in the real World and do an appraisal of which would be the most practical or useful.

I would also advise doing some simple sketches. As a minimum a basic plan and sections through both orientations showing ground levels. The plan should show any drains or trees etc.

 

[Gavin31]

Hi John , thanks for your input.

Its not essential for me to determine the exact cause, as you said it would require a proper investigation to find out. I just need to explore the possibilities and do a write up on each, whether or not they are the cause is irrelevant. That said i would like to determine the most likely cause.

Im sorry that the pictures dont help, if you can tell my what type would help ill gladly take them.

 

[jeds]

Well, they are just photos of a crack. They could be photos of a crack on any garage wall. More useful would be (additional) photos of the overall scene showing context (by that I mean location and extent of the crack on the garage) and how the garage relates to surroundings.

 

[Gavin31]

Ah ok, i put up another 2 there, its kind of difficult to get proper shots as there are bushes in between the 2 houses and thats ideally where i would take the pictures from...

 

[luisdesign]

Ah ok, i put up another 2 there, its kind of difficult to get proper shots as there are bushes in between the 2 houses and thats ideally where i would take the pictures from...

This is also why having a plan is a must (preferably scaled). This will let you clearly describe the context even where photos might not.

Site context (and history) is incredibly important... you may be sitting over an old mine, or right under a flight path or right beside a busy rail line etc.

 

[Gavin31]

Im going to head in to my Local Authority on Monday and see if they can provide the original plans for the area as i havent a clue where the pipework is.

Ive done a visual inspection on all the other houses on my row and none have the same issue. To me this indicates poor ground compaction on our site or inadequate foundations/ s&c screed

 

[luisdesign]

For the purposes of your module, what are you expected to produce?

 

[Gavin31]

"The student is required to select one defect within a domestic building. It must be of a size or magnitude to engage interest and require a range of knowledge and information sources. The report must follow investigation, symptoms, diagnosis and remedial action, recommendations."