Quality Control of the Slab's Concrete - The Report

After much requesting, the quality report of the slab's concrete (as detailed in this post - Quality Control of the Slab's Concrete) finally arrived!

My personal suspicions are that these reports are generated regularly within Boral, it was the fact that an end client was requesting a copy is what threw them.

I never got any sense that neither should i not be asking nor should I be receiving a copy, more of a how do we get that?

Frame overhang issues

I've seen a lot of posts on the forums about frame overhang, where the frame overhangs the slab by an amount, sometimes in excess of the building standards.

A lot of the owners are getting very upset by this.

We had one location where this happened to us (the front corner of the study).

A small amount of overhang.

I asked our independent inspector about it: "Should I be concerned?".

His answer was interesting, not quite what I expected, so I thought I'd share it here, hopefully to alleviate some stress and anxiety of owners.

Even if it is not to standard, even if it should proceed to VCAT/legal action, essentially what it boils down too, is this: will it functionally work?

Quite unexpectedly, pragmatism wins!

In the case above, I'd suggest that the overhang does not functionally impare the overall functional requirements of the frame. The inspector was not worried about it. No rectification was performed.

So hopefully, this real world example provides some information that helps ease any stress and anxiety that other owners many find themselves facing, should they experience a similar situation.

Post Slab Pour Site Preparation.

The slab had been allowed to cure over the weekend. I drove past the block on Monday afternoon, not expecting to see anything, however, I was surprised.

There was some post site pour site preparation going on. The ground the house is on is primarily clay, so to make the builders life easier, they spreading gravel around the edges of the slab. I hope that it will be removed by the time that they finish, as it's one more thing that I'll be digging through...

A baby one! Can I have one?

 

The gravel to help with the clay.

A once clean slab is no more...

 

The edge of the garage.

The alfresco, looking towards where the pool will be.

Looking into the garage.

The entrance.

Quality Control of the Slab's Concrete

For those of you who have paid attention to the recent press about slab issues (particularly out west of Melbourne), you may, as I have, wondered about what, if any quality control was in place for the slab and it's concrete.

Our particular slab was thicker than normal. This particular thickness that I'm talking about is the thickness of the concrete above the waffle pod. Most are 85mm or 100mm. Ours was 125mm.

In addition, the comments from both our independent inspector and the guys who put it in place also said that it was a very heavily engineered slab. More so than usual. This was in relation to the amount, and gauge of mesh put in place.

The engineers who designed the slab, it's piering etc had their reasons for doing so. Who knows! I'm not an Mech/Civil Engineer. But both my brother (Mech Eng) and my father (Mech Eng and Metalurgist) are engineers...

All of that is fine, but the engineer would also have specified the strength of the concrete itself. It is specified in MPa (Mega Pascals). What if the concrete itself was not up to specification?

I was most surprised, and utterly thrilled to see that the concrete itself being tested.

How? They take samples, let them set, and the test them. Destructively. Which is the only way that it can be tested properly.

There was a man from Boral who was taking samples of the concrete, from each truck and making testing samples.

Ever seen a thermometer in concrete? Now you have.

Samples from each truck were taken and placed into these setting pots. They each had a base and split down the middle.

They were then vibrated to allow the concrete to settle and then get rid of all air bubbles etc.

All of the samples were gathered together, and would be allowed to fully cure for seven days before being destructively tested to verify the concrete strength.

I asked the man taking the samples, how you would fix the concrete if it was not up to strength. He smiled and simply said "With a jack hammer!". Which would be the only thing you could do, as there is nothing that you can do once it's set.

So, with all of this engineering and testing, I'm hopeful that the slab issues that have plagued the building industry of late have been put to rest.

NOTE: As a follow up, please read Frame Overhang Issues for a discussion about slab issues and how they can be resolved.

Another follow up NOTE: The quality report has been received! Please read Quality Control of the Slab's Concrete - The Report for details.

Slab Pour Day!

The day started early, at 7am, with a call from Matt, PD's Slab Mgr telling me that all issues had been rectified (as expected) and had also been checked by their engineer (most unexpected). He also said that there were several concrete trucks lined up and ready to go!

We had a look at around 9am to see what progress had been made. There was one truck filling a line pumper, with another one waiting.
We stopped to talk to one of the Boral concrete truck drivers. I asked him how much they held. If I remember correctly, he said that he can hold 5.8 cubic meters, but they only allow him 5.4. I do not know why.

I asked Matt how much concrete went into the slab. 84 cubic meters! I also found out that they went over double (25.8 instead of 12 cubic meters) the amount of concrete for the piers.

The back of the slab had been poured, starting on the garage. The second guy is using a vibrator that helps settle the concrete.

Lots to do.

We next popped around at 3:20pm. The slab had been poured and they were now applying detailing finishes (edging, finalising the surface etc). As some of the concrete had set enough for the support boxing to be removed.

Detailing the portico as it joins the house level.

A little more...

Pulling down the supports.

We came back around around 5pm, to see how much things had progressed.

Sitting high above ground level. The rear of the house is even higher.

The garage.

Looking across the garage to the rear.

The alfresco. There is meant to be a drain somewhere in there...

Looking from the rear to the front.

Looking from the rear to the garage.

Looking through the garage to the rear.

All detailing finished.

Finally! A wide enough angle to show everything! All done!

We were there until 6pm, and they were only just finishing up. That's an 11 hour day, of hard, back breaking work. It's not a job I could do (or want to do for that matter).

Earlier in the day, we got them all a large subway platter of food and some drinks. We ended the day with a carton of Crown Lager. They were totally gob-smacked! But happy enough to receive it as well. Evidently it does happen very often... I don't think that it hurts to show a little appreciation.

Matt gave me a call late in the afternoon letting us know that he was done, and that we'd soon be contacted by our site supervisor who would oversee the rest of the build. I gave Matt some positive feedback, which he greatly appreciated.

The day did not end there though. We arrived home to find an email in my in box. It was the invoice for the slab...

Slab Preparation. Day 3.

I arrived just before 3pm on Thursday to find that significant progress had been made. The polystyrene waffle pods had been put in place. The gaps between the pods form channels where the concrete will drop down into, giving strength. Concrete can take huge compression stress. Concrete does not deal well with tensile stress. To assist the concrete do deal with tensile stress, steel mesh and reinforcing rod is placed within the concrete to take the load. Most of the thicker reo-rod was placed in the channels. The mesh is lifted off the waffle pods, to be in the top third of the concrete. Both the guys laying the slab out, and the independent inspector where quite taken aback and surprised by the engineering of this slab. The slab itself is simple, as in not involved, but it is very heavily engineered. Heaven help anyone who wants to demolish this slab!
 

The initial laying out of the mesh on top of the waffle pods.

The mesh being lifted off the surface of the waffle pods. This also shows the width of and the depth of the solid concrete around the edges of the slab.

View from the front showing the garage and portico.

Closer inspection of the edge and corner.

The extensive bracing put in to support the slab.

Detail showing the reo-rod on the bottom being lifted off the bottom of the slab so that it's actually in the slab itself.

Detail showing the cross bracing in the narrower channels.

All of the supporting struts to support the boxing around the edges of the slab are manually put in place. Nailed, drilled or screwed into place. The mesh is put down, manually, and then lifted, manually, onto the round plastic supports shown above. These supports give the proper clearance above the waffle pod, and below the surface of the slab. It is a huge amount of work to be done. It is all manually performed, and by the end of the day, having been bent over for most of it, they are quite well exhausted. It's not a job that I could do.

It was at this point, before the pour (tomorrow) that we had David from Darbecca inspect the slab preparations. He was very pleasantly surprised that there were very few faults in the installation; all of which are only generally rectified (waffle pods that had moved etc) on the day of, or as the pour occurs.

I would also like to thank Matt, PD's Slab Mgr for being so approachable and responsive. I did not get the inspection report until about 7:30pm, and it was only then that I realised that I only had Matt's phone no, not his email address. I needed his email address so that I could forward the report to him. Matt was responsive to SMS's at 8pm at night, and I forwarded him the report. I could not ask for more!

So all in all, we're happy and excited about the pour for tomorrow!

Slab Preparation. Day 2.

Today, the guys were continuing to prepare the slab.

I popped around twice through out the day to see their progress. In the morning, they were putting the wood boxing around where the edge of the slab would actually be.

All of the support bracing is yet to be put in place.

 

Looking at the rear of the slab, it is very high off the ground.

Some very heavy reo-rod and normal mesh. Apologies for my finger!

All of the different types used.

When I arrived in the afternoon, they had completed the boxing and were well into the laying of the moisture barrier (thick black plastic) used to protect the slab.

The bracing has been completed. You can see the height of the slab.

Still lots more to do.

The pour is due for Friday and there is still much to do.

Slab Preparation

This morning, we drove past the block, to find that the previously dumped gravel had been spread out in preparation for the slab. Foundations for the foundations as it were.

Gravel base for the slab.

Odd though it sounds, the house is starting to take shape; in that we can now really see how big it is and where it's going to go.

Drainage completed! Day 5!

No, it is not a dog agility course!

It's the long overdue (through no ones fault) completed drainage!

Yey! Slab, here we come!

Looks like an agility course!

Finished!

Oh, and all of the rock has been removed as well!

Drainage progress. Day four.

This morning I went to check the block to see what the status of the drainage was.

To my surprise, we had a second, larger digger on site. This one was brought in to break the rocks up so that they could be actually picked up and put into a truck to take them away!

It had this jack hammer attached to it.

The jack hammer.

It makes pretty neat work of the rocks.

The split rocks.

Unfortunately, I did not have my boys with me, so I had to take this instead.

I was going to name this blog post "Ten years of hard labour", as that is about the time I think that it would have taken me to breakup and move these rocks by hand! :)

Drainage preparations

Last night, on her way home, Heli drove past the block and said that there was a big pile of dirt in the driveway.

Huh?

Upon investigation the next morning, my boys and I checked it out.

It is red scoria. One of the really strange things that I find about building is that at least in the case of the piering and drainage, it is documented after the fact. Whilst I understand the need for flexibility, as witnessed by the piering adventures, can't we at least have a plan??? Well, no. Not in the case of drainage. I've made some requests for placement of drainage risers. I'd have liked to have seen a plan first so that I could see what I'm getting and what I needed to add where I needed it. Nope. In this case, it is all done after the fact.

Once it's done, I'll be requesting a formalised plan drawn up. Darren from Darbecca, our independent inspector, has strongly recommended that we get all plans (piering and drainage) documented within seven days of being done. This way it's all fresh in people's minds. Or more to the point, if things go horribly wrong, and you find yourself in a VCAT hearing in 3-5 years time, the judge will (and has) asked in real cases "Why was it not documented?". It's all about protecting yourselves.

Power To The People, Reprised

Whilst I was not looking, someone snuck onto our block, dug a trench:

And put the power cables in!

In the right place too! On the outer garage wall. Which is always a bonus.

Site Cleanup - Part 2

Hmmm. I spoke too soon.

I was right, evidently, there was too much dirt in the second truck load. SO much so, that I think he ended up taking some out of the trick so he could fit his digger into it.

I do not recall seeing this there yesterday...

Site Cleanup

Given all of the rock, and the left over concrete (from the cleaned pump lines), I was wondering when they'd clean it all up before the drainer had to start their job.

My mum lives a few hours away, and she happened to be down and popped in to see me. She had also not seen the block, so I took her around to see it.

When we arrived, we were pleasantly surprised to find that the site was being scraped clean!

A small digger. It just managed to move the larger rocks. I want one!!!

The man driving the digger was nice, he also said that they did all of the PD work in the area. He also said that he'd managed to fill this truck twice!!! He may have needed a third trip, as he may not have had space for his digger to go in the rear trailer. The type of fill (clean dirt or with broken glass, rock etc left over from the demolition) determines where the loads of rubbish go. In this case, it was a 45 minute trip to empty the loads; that's where the day goes!

At least two of these loads!

So in a few days, we've gone from this:

Before.

To this:

After.

Now, at least the drainer will not have to dodge all of the surface rocks. He's going to have a hard enough time with the underground ones!