House slab is exposed all along the sides. Is this right?

eltkris · May 09, 2019 2:59 pm

Just wondering if anyone can shed some light on this. We have been in our house for 6 months now. We spoke to a Landscaper who also has experience in the building industry. He said that our builder should not have left our Slab exposed the way that it is. As you can see below, they left the bottom of our house all around the slab exposed like this, so you can see the black plastic, and in many areas the plastic has torn away and the slab itself is exposed.

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On top of that, you can see they placed our Hot water unit on a bunch of Bricks instead of on a proper concrete slab. Our landscaper was surprised that we were given an Occupancy Permit.
The inspector that gave the permit didn't seem to have any issue with this. The only thing he said that had to be done, was that the ground had to be raised at all of our entry points so that the step down isn't too much. So that's what the builder did.
Does anyone else's new house build look like this? Have they failed to meet some code or regulation that I can raise with them?
I'm wondering if there's anything I can do to make the builder bring in soil to raise it all. We're now having to spend more money on soil for our landscaping to effectively raise the land all around our house.

hoody_s13 · May 12, 2019 9:37 pm

Hi eltkris,

What you have there is perfectly normal.

The exposed plastic sheet is a Damp Proof Membrane (DPM), which is situated under the slab to prevent rising damp, or moisture being pulled through the slab and into the habitable space inside. For obvious reasons this is a good thing, for general health and to preserve building materials in contact with the slab (ie timber frame).

Technically, the plastic can be cut at ground level, and where it runs under the external brick coarse - exposing the concrete edge.

The other benefit of having an exposed slab edge, is to detect the entry of termites into the property externally.
Suitable termite measures would be in place around service penetrations (e.g. sewer pipes) in the concrete slab, so no other way for them to get into the building, except around the outside (if the slab is monolithic, or poured in one go).

However, most people are not aware of this benefit, so will fill soil up to the junction of concrete slab and first coarse of bricks (or cladding for timber frame), to hide an ugly feature of the wall. Assuming this is also why the builder has left the plastic in place, to prevent moisture absorption through the soil in contact with the slab edge.

I'm not aware of your full wall makeup (assuming brick veneer), but it would be safe to assume that a perimeter barrier has been installed under the internal timber frame, or where the first point of structural timber frame begins in the dwelling (eg. First floor brick veneer, ground floor cavity brick).

Check your meter box, or documentation provided with the Occupation Certificate. Both should contain details of the treatment applied. If a physical perimeter treatment has been applied, then I would say OK to fill the land as proposed, up to the junction of the slab edge/external brick.

Otherwise (its unlikely a perimeter barrier has not been installed), maintain a 75mm exposed slab edge (cut plastic in this case), which will allow an annual termite inspection to check for activity around the building.

Additionally, no problem with the HWU, granted the base is solid that it's sitting on.

Rhys

MyFirst · May 12, 2019 11:17 pm

eltkris

Just wondering if anyone can shed some light on this. We have been in our house for 6 months now. We spoke to a Landscaper who also has experience in the building industry. He said that our builder should not have left our Slab exposed the way that it is. As you can see below, they left the bottom of our house all around the slab exposed like this, so you can see the black plastic, and in many areas the plastic has torn away and the slab itself is exposed.

Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅

On top of that, you can see they placed our Hot water unit on a bunch of Bricks instead of on a proper concrete slab. Our landscaper was surprised that we were given an Occupancy Permit.
The inspector that gave the permit didn't seem to have any issue with this. The only thing he said that had to be done, was that the ground had to be raised at all of our entry points so that the step down isn't too much. So that's what the builder did.
Does anyone else's new house build look like this? Have they failed to meet some code or regulation that I can raise with them?
I'm wondering if there's anything I can do to make the builder bring in soil to raise it all. We're now having to spend more money on soil for our landscaping to effectively raise the land all around our house.

U should be happy mate.
The slab membrane is so perfect.
Never seen a completed house with such perfect slab membrane.

And expose slab edge. Yes is normal most builder just leave it.
Some will just cover it up with some token soil. But at the end of the day landscaping will cover it up.

However what I just learned recently. U are suppose to leave at least 50mm of your slab edge so u can see termite attack.
However nobody wants to do this though since its ugly.

hoody_s13 · May 12, 2019 11:36 pm

MyFirst just so your aware for your own property, a minimum of 75mm exposed slab edge is the magic number per AS3660.1... however most pest inspectors will tell you 80mm-100mm.

The standard notes you only require one method of protection (ie. Case of a building perimeter - either exposed slab edge, perimeter chemical impregnated sheet, in soil chemical barrier by way of refillable reticulation system, etc).

Rhys

eltkris · May 22, 2019 12:58 pm

Thanks for the replies, everyone. Glad to hear that's pretty normal. This is the second house we have built, and our last one they did not leave it like this.
Now it makes sense, because they actually didn't use any termite protection at all. I guess their method of protection, is leaving the exposed slab edge and expecting that we won't cover it up. I'm not surprised.

SejaeD · May 22, 2019 2:28 pm

eltkris

Thanks for the replies, everyone. Glad to hear that's pretty normal. This is the second house we have built, and our last one they did not leave it like this.
Now it makes sense, because they actually didn't use any termite protection at all. I guess their method of protection, is leaving the exposed slab edge and expecting that we won't cover it up. I'm not surprised.

my money is on that plastic being a form of termite treatment,

AS 3660.1.2000 requires all homes to have an approved form of termite treatment. Would be interesting to see what the writing is on the plastic

hoody_s13 · May 22, 2019 3:10 pm

[quote="eltkris":358j09k3]Thanks for the replies, everyone. Glad to hear that's pretty normal. This is the second house we have built, and our last one they did not leave it like this.
Now it makes sense, because they actually didn't use any termite protection at all. I guess their method of protection, is leaving the exposed slab edge and expecting that we won't cover it up. I'm not surprised.[/quote:358j09k3]

Has the builder confirmed that no termite protection has been installed?

Could you confirm the makeup of your dwelling? Brick veneer, double brick, combination over two floors? Assumed timber frame roof?

If no 'structural' timber is located in the dwelling, then technically no requirement to comply with AS3660.

Otherwise, at a minimum you should have the 75mm 'exposed' slab edge right around the perimeter (cut plastic and expose slab edge). Services penetrating the slab should also be fitted with rated collars to prevent termite entry that way.

Alternatively as mentioned above, the DPM may be impregnated with appropriate chemicals per the Standard, so all OK as the entire underside of the slab (whole building) is protected.