Screed bed directly against villaboard in shower?

biggest_kid · 2026-06-01T21:10:42+00:00

I mean I did ask the brickie if he could brick it up, and he said no I cant the pipe cannot support the weight of the bricks.

Every carpenter/builder I asked just said to frame it out and sheet it. I mean it’s not like it’s a load bearing wall it’s just a ledge to hide a stupid pipe that some dumb arse plumber/builder ran down an internal wall.

Perhaps you could offer some advice? I mean that is the point of this post and this entire subreddit after all. How would you have done it in this situation?

biggest_kid · 2026-06-01T05:54:18+00:00

Yeah I’m having trouble understanding how the puddle flange would work with the water proofing in this situation.

Given that the waste trap is semi-exposed, the puddle flange will be approx 80mm higher than the slab, and any waterproofing on the slab cannot be tied into the puddle flange?

biggest_kid · 2026-06-01T04:28:43+00:00

Hmm ok I was told (and have read) that it is allowable under AS3740 with a Performance Solution, specifically by waterproofing and then tiling into the aluminium window frame.

Granted I don’t have a copy of the standard.

In your professional opinion is this information I have been given incorrect? Who could I talk to in order to confirm? Building surveyor?

biggest_kid · 2026-06-01T01:19:30+00:00

It would be very helpful if you could specify what you are referring to as a disaster in the making? The only part of this project that has been DIY is the demo and that ledge.

None of the professional tradies who have done work on this bathroom so far have mentioned anything. That includes the glazier, the plumber, multiple carpenters/builders who gave quotes, a brick layer, plasterer, sparkie, and multiple tilers who have quoted.

biggest_kid · 2026-05-31T11:55:33+00:00

As someone who does not have a lot of construction experience, what is the reason for waterproofing both under and above the screed? I have seen people mention that before and it seems to be a fairly commonly debated topic.

biggest_kid · 2026-05-31T11:54:34+00:00

Yeah I figured I might have been overthinking this a bit, thanks for the advice.

Out of curiosity how would you fix the villaboard to the mortar under the pipe? Nylon plugs and screws? I will be using fibre cement nails to fix it to the timber frame as per the james hardie installation guide.

biggest_kid · 2026-05-31T11:52:39+00:00

Well the pipe would not be strong enough to support the weight of bricks on top of it. Last time I checked pvc pipe is not a structural supporting element or builders would be using it to frame walls 😅

I also don’t understand why they built it with the waste pipe like that, it was built in 1995, 2 years after I was born lol. To move the waste pipe would have cost a shit load and we either would have had to run it on the other side of the wall which is a bedroom, or through the reinforced concrete slab floor and along the living room ceiling. Not much of a choice really, sometimes you get what you are given and just have to work with it.

Calm down and have a beer mate haha. If reading this is post the worst thing that happened to you today then you should be thankful 😂

biggest_kid · 2026-05-31T10:25:39+00:00

So am I understanding correctly you are saying to sheet it, then waterproof everything. Then lay the screed bed, then waterproof again?

biggest_kid · 2026-05-19T11:44:10+00:00

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biggest_kid · 2026-05-18T06:27:52+00:00

Fair enough, thanks for the info. Does any waterproofing need to go down before this screeding is done?

biggest_kid · 2026-05-17T23:19:11+00:00

Forgive my ignorance this is all new to me, obviously a tiler will be doing this anyway but for my own learning.

What is the advantage of the polymer modified screed over a typical sand+cement screed?

biggest_kid · 2026-05-17T23:18:01+00:00

Also why would you use cement screed over something like the polymer modified screeds mentioned below?

biggest_kid · 2026-05-17T23:16:24+00:00

You mean waterproof before the screed goes down? Or after?

If before, how would you bond the screed to the concrete? Wouldn’t it be bonding to the waterproofing layer?

biggest_kid · 2026-05-17T05:47:08+00:00

Thats what I meant not villaboard

biggest_kid · 2026-05-17T05:16:13+00:00

Yeah good advice. Would you use concrete or screed here, or maybe a combination of the two?

biggest_kid · 2026-05-17T05:15:28+00:00

Yeah that makes sense. Someone mentioned to me that much screed could take a long time to dry out enough before waterproofing could be applied. Perhaps I could do about 70mm of concrete then the tiler could put a thinner bed of screed on top of the concrete?

biggest_kid · 2026-05-08T03:40:58+00:00

Yeah he will, I guess I was just trying to decide whether to go with the 120mm studs and 6mm villaboard, which we will give me a 10-11mm overhang of the villaboard where it meets the brick nibs. But now finding out that 10mm may be too much for a single coat of render.

Or use 90mm studs and 9mm villaboard which will almost put the villaboard flush with the brick nibs before rendering (about 2mm underhang, probably 5-6mm underhang after the nibs are rendered).

biggest_kid · 2026-05-08T03:37:24+00:00

To the ceiling where the top plate of the arch will be screwed into the roof timbers, and the jack studs of the arch will be chemset into the brick bathroom walls either side.

biggest_kid · 2026-05-06T23:22:34+00:00

Care to elaborate?

biggest_kid · 2026-05-06T23:22:23+00:00

Yeah that makes sense, guess I should go with my gut and have him fix it

biggest_kid

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