Walls and doorframes moving

[Nashi]

We own and live in a 2 bedroom unit with a shared wall adjoining another unit. The date of build was 1970s.

We've owned the place for about 18 months, and the previous owner re-stumped it just prior to selling it to us.

In that time we've had a number of issues:

2018-19 Front door not closing properly, gradually worsening over time, and cracks forming in the cornices around that same area.

2020 - Back door not closing properly, gradually worsening over time, larger cracks forming in the rendered wall on the outside either side of this back door frame, as well as a gap forming across the top of the door frame and the rendered wall.

2020 A zigzag crack in the brick mortar on the adjoining wall between ours and the next unit.

- A few small hairline cracks in the ceiling plaster.

So far we have shaved a bit off the front door and haven't had any further problems with that.

But the back door has been a real problem. We've shaved that door a few times over the past couple of months and it keeps getting worse, to the point now where we can't close/lock the door at all, which obviously poses a security problem.

If it wasn't for this door not being able to be closed, it's not really causing any 'functional' problems, but obviously this indicates some deeper issues with the building structure.

The problem seemed to be exacerbated by the extremely hot and dry Summer we just had, as well as the very heavy recent rainfall in the past 2 weeks. The storm water drain runs along the front of our unit (past the front door) and no blockages or damage has been found.

The sewerage runs along the back of our unit past the back door.

We are unsure what action we need to take from here, taking into consideration that our stumps are pretty much brand new. We really don't have any money to work with, especially now considering my partner is on a job keeper salary due to COVID19.

Any knowledge or advice on this would be greatly appreciated.

Thanks.

[JDE]

Rowmn

My parents had a similar problem in an older house. Their problem was changing moisture levels in the clay resulted in repeated movement of the house footings. The advice they were given was to stabilise the moisture in the soil by either a. Improving drainage and trying to keep the area dry This included the idea of paving or putting a path around the house  or b. Putting a garden around the house to maintain the moisture level. Being a unit may complicate the matter as you will need to work in conjunction with others. Sorry not a quick fix. 

James

[Jason]

@Adam_W 

Is there any expert advice you could share with @Nashi?

Thanks,

Jason

[Nashi]

Thanks James. I think that could be a good solution for the front door as it is currently just dirt/lawn up to the edge of the house, but not the case for the back.

The back is completely covered by a deck and pergola, no direct exposure to rainfall, which now makes me wonder if it's a sewerage leak problem? as the sewerage pipes run along that section of wall. However this doesn't really fit with the seasonal changes causing the issue, as sewerage would be a fairly consistent flow.

[Adam_W]

Hi @Nashi 
Okay, can totally relate to this as we have movement in our place which has taken me a while to work out.
Everything you're describing tells me there is some movement with footings.
So, the property was re-stumped but do you have an idea in what way?

'Stumps' are in many respects a two part beast where each part works together. If one part isn't right then the most common issues are exactly what you've described.
The two parts are...
- the posts themselves - they need to be the right dimensions and number for the load

- the actual footing, the bit you don't see below ground.

We're doing a lot of work here and I know the dimensions of our pier holes - minimum 600 wide x 900 deep.
We're on a spongy clay top-soil/silt that is then underlain by solid clay so that size is pretty typical. Our posts are then all 90 x 90 steel.
I finally worked out our movement issues. They had me very concerned as we have added a lot onto the original house so I was worried we had messed around with the loading & stress points but turned out to be simpler than that...
The original posts are steel and 20-years old. Some of them had corroded at the base. From a quick inspection they looked okay but the fact is the rust was weakening the posts and they were slowly compressing dropping as they did so.
I now have to replace quite a few which is a job that's not difficult but laborious & a bit hair-raising as you need to jack the house up with acro-props before removing the old post & replacing it.
The trial one I've done so far I used an adjustable top post so I could literally wind the house up...
What it sounds like to me is that your actual piers, the concrete bits, aren't of an adequate depth or size for a reactive clay soil. This could probably be rectified by digging around them and making each one bigger, sort of under-pinning.
I would however be seeing if you can find a suitably qualified engineer to look at it. Cynical I know but I've generally found the best people for this sort of advice or report are those that do not have a business interest in fixing the problem for you if you get my drift...
Another thought to is cross-bracing. How tall are your stumps? If they are more than about 750mm to 1000mm then there should be a few cross-braces between them. This is storm-proofing but also helps with movement.
As discussed... drainage may help too but most often deep clay will just be absorbing subterranean water that may have come from elsewhere.
Okay, not sure if any of this helps but food for thought.

[Nashi]

@Adam_W Thanks for taking the time to respond, that's really helpful. Sounds like you've had quite an ordeal yourself.

We weren't able to contact the previous owner to ask anything about the re-stumping job, but from what I can tell, the stumps are made of concrete, not sure what dimensions they are. Our unit hasn't had any loading changes, so I assume they would have just gone with the original dimensions.

As for stump height, no way they would be that tall, our unit sits very close to the ground, it's a slightly sloping block but I'd say no more than 500mm from earth to joists.

I guess our next move is to get a structural assessment done and see what our options are from there.

[Adam_W]

Hi @Nashi, no worries. Shared experience can often be useful!
You know... after undertaking a major reno & extension (which we may actually finish one day...) it all becomes bit par for the course. Best laid plans and all that.
Ok, can picture the type of situation you have. The fix for these things can be as simple as one nice big beam and a few new piers but get someone to assess it for you.

I always say the single most important DIY skill is knowing when it's time to down-tools and call the professionals in.

Let us know how things pan out & good luck.

[ErrolHunt]

Hi Nashi. I can relate to this! Seddon (western suburbs, Melbourne) is notorious for a thick clay layer that responds to changes in groundwater. Thus, constantly moving houses/lots of cracks/door issues. The solution in new houses is insanely deep stumps (6 feet!). Our house is old and various bits have been re-stumped at various times, adding to the variation in movement of different walls/doors as groundwater moves through the clay, and particularly in Spring/Autumn. (There's no way to control groundwater of course, which depends on surrounds sq kms). At least we're a wooden house, so less issue with cracks. I'd love to see a technical solution to this as far as moving doors though: hinges/latches that were more easily adjusted for example, eg via hand-turned screws that could adjust up/down, back/forward by a few mm at a time. We're constantly tweaking here, requiring multiple sets of holes for hinge screws etc. I'd happily shell out 10x the cost of normal door hardware for the trickier doors, if such a thing had been invented. (Perhaps someone in Seddon should get into this field!)