Thread: Trying to find some specifications DPC

Originally Posted by zacnelson

This sounds like a frustrating predicament!

I just have a quick question, how do you know exactly where the DPC is on the brick wall? I can't imagine it would be sticking out through the mortar? Or did you personally build the wall and therefore can remember which course of bricks it was in? (Please excuse my ignorance)

Sort of explained here.

Originally Posted by fraserde

The fax didn't get sent, he claims he'd run out of ink, maybe he has.....

why does he need ink to send a fax

Originally Posted by Terrian

why does he need ink to send a fax

Not sure but he still hasn't sent it.

Again not sure if it's a sign of his dis-honesty or incompetence

Originally Posted by fraserde

Not sure but he still hasn't sent it.

Again not sure if it's a sign of his dis-honesty or incompetence

I go for options 1 & 2

Originally Posted by Terrian

I go for options 1 & 2

He also said that half the concrete in Melbourne was poured like that and if everyone expected the BCA to be adhered too, where would we be.

I said I don't really care if 90% is dodgy, it isn't mine. Just because others put up with it why should I?

Id be checking the other jobs around Melbourne.

If you had photos that would be good.

Is the slab under roof cover?

Is there an under slab membrane such as plastic?

Does that plastic turn up the back of the concrete between the wall and the slab?

Is there fall on the concrete? How much over what metres?

What was the MPA of the concrete?

What does the existing DPC consist of?

How high is the DPC above the ground?

How high is the concrete above the DPC?

If it is double brick and the principles of how cavity water egress is understood, really there should be no DPC course to the outside leaf of brickwork as that is the structure that it exits.

Is the house footings a slab step down?

Photos would be good.

Is the slab under roof cover? some of it, it goes fromlevelish with the DPC from inside the alfresco to 45mm below outside

Is there an under slab membrane such as plastic? No I believe not

Does that plastic turn up the back of the concrete between the wall and the slab?

Is there fall on the concrete? How much over what metres? Plenty of fall ( the concrete was used to create it, around 2ocm's thick)

What was the MPA of the concrete? 25

What does the existing DPC consist of? Plastic

How high is the DPC above the ground? two bricks

How high is the concrete above the DPC? Levelish maybe a mm or two

If it is double brick. Single

Is the house footings a slab step down? Yes I think.

The letter from his engineer.





I received from you by email a set of photographs of concrete paving which I am informed was carried out by your company.
The top surface of the concrete had an impressed stencilled pattern and was coloured with a grey pigment.
You have informed me that your client is claiming that the paving does not comply with the Building Code of Australia (BCA) because it less than the minimum distance below the damp proof course (DPC).
The dwelling I was informed was constructed of a timber frame on a concrete slab with a brick outer leaf.
The photographs sent to me show weepholes above the level of the paving.
The BCA in 3.3.4.5 Damp-proof courses - installation (c) (ii) states that DPC should be 75mm above the finished surface level of adjacent paved, concreted or landscaped area that slopes away from the wall.
This section of the BCA specifies the height of DPC above, what is implied here, existing paving, concreted or landscaped area. Also, there is no mention of weepholes being 75mm above the level of the paving.
The photographs received show weepholes. In some instances the weepholes are less than 75mm above the concrete paving.
Weepholes, or open vertical joints, are installed in the outer brickwork to allow water that had entered the cavity between the outer brick leaf and wrapped timber frame to escape. A plastic sheet is then fixed at the bottom to the wrapping material and incorporated into a lower mortar joint between two courses of bricks. The weep holes are vertical openings above that mortar joint which contains the plastic sheet. The vertical openings are between bricks where the mortar to form vertical joints has been excluded.
The plastic sheeting will be considered as a damp-proof course If it complies with other requirements of the BCA. If it's black polyethylene film which is what is used for the plastic film it needs to 0.5mm thick, of high impact resistance and low slip. It also needs to extend through the whole thickness qf the mortar joint.
But if the plastic sheeting acts to remove water from the cavity through the weephole, than it can not be an effective damp-proof course because water running down the plastic sheet to the weepholes is free, in vapour form, to move up the bricks.
This notion is confirmed in part 3.3.4.3 of the BCA, "Cavity ventilation and drainage". Here it states that weepholes must be created in the course immediately above and DPC or flashing... except, (iii), where a damp-proof course is installed in accordance with 3.3.4.5. Therefore, since there are weepholes, it follows that there a DPC is not required.
Firstly, it is not known if there is, in fact, a DPC below the weepholes, secondly given that there are weepholes it follows that there is no DPC because then weepholes would not be necessary if the DPC was done in accordance with the BCA, thirdly a DPC would not be effective, but more importantly, the paving as long as it is below the weepholes does not interfere with the function of the weepholes.
I noted that isolation joints were installed between the paving and brick walls and that saw cuts were placed at appropriate locations. The diagram provided to me shows that the saw cuts were placed at appropriate locations to be functional in controlling the occurrence of shrinkage cracks. I have been informed by you that no shrinkage cracking has occurred. The installation of the isolation joints and the location of the saw cuts (control joints) appear to comply with the guidelines of Australian Standard AS 3727 -1993 Guide to residential pavements.
Given the information I have received including the photographs and diagram and given the requirements of the BCA and guidelines of the above mentioned Australian Standard the paving has been completed in such a way so it does not violate any BCA requirements or Australian Standard requirements and does not interfere with the ventilation and drainage system of the cavity in place,
I trust this information is of assistance to you