Build Your Own House

We want to avoid penetrations through our slab, to minimise the risk of termites entering via plumbing, so we plan to have all plumbing going through walls rather than the slab. To get the shower waste water going out through the wall, we have come across 2 options, neither perfect:

Build the shower up to leave enough room between it and the slab to have an S bend. This would make an inconveniently high step.

Or have a plumber put an inline bladder made of rubber (or similar) that the waste water goes through under the shower, and which stops smells coming up into the shower, as an S bend does, but which doesn't need such a high step. The negative aspect of this idea is that I presume the bladders have a lifespan (the plumber who told us about it guessed 10 years), which then becomes a maintenance problem later.

Has anyone got any other ideas of how to do this (or comments on the above options)?

Hi Einadia

We did exactly the same thing with our build. We did not want to puncture the slab so all our pipes are through walls.

We elected to build a platform in our bathroom with an additional step into the shower. It works well for us and we are happy with it. This also accommodates the waste for the bath.

The toilet is installed on the slab and the bath, shower and vanity on the platform floor.

The EHO insisted that we have a separate pipe installed for the removal of any potential smells. This is plumbed in under the vanity and again runs through the wall outside and then extends upward through the eave.

I have photos on my website if you want to see the bathroom under construction and the end result.
The website is http://www.timberframemuddie.com Click on the Timberframe house link and then the Bathroom photos , dated June-October 2009 and 2010.

You are welcome to PM me if you have any questions.

Ilze

Excellent question. It seems to me that 90% of the termite precautions are related to either slab penetrations or stupid wall details designed to hide the edge of the slab for purely aesthetic reasons.

I know nothing about the bladder solution so I can't comment on that.

I do wonder about floor wastes. Doesn't the BCA require floor wastes for bathroom and laundry? In which case just using a step up to the shower recess isn't going to cut it. Floor wastes don't actually have to run into the main sewer line because they are only there to cope with overflows from your bath or washing machine.

As far as I can see there is no reason why the s-bend should be inside the building - assuming our shower is adjacent to an external it should be acceptable to run separate waste lines through the wall and then into an s-bend. So what we are looking at is getting a 40mm pipe below floor level and through the wall without any slab penetrations below ground level.

One solution would be to thicken the bathroom slab to make room for a horizontal run of pipe. Assuming your floor slab is 100mm thick you can (probably) safely cut a channel 20mm deep for your pipe run. If you then pour a 40mm granolithic slab over the top that would allow for a 15-20mm cover over the pipe. You could maybe do a terrazzo finish for the topcoat and eliminate floor tiles.

Alternatively you could build a compressed cementfibre floor using 50 or 70mm joists fixed direct the slab. You would then seal the floor as for framed construction and tile over.

Either way you get a small step up into your bathroom. You could lower the whole slab below the bathroom (as for a sunken lounge) to eliminate this step but your grano guys will hate it and will probably charge through the nose and then stuff it up.

All just my opinions of course and worth every cent you paid for them Check with your engineer and plumber.

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Bruce
Draftie

Good one Einadia, make it simple is always best. Having no pipes sticking up makes screeding the slab easy, however, if you did have termites come up a pipe intrusion through a slab into your floor waste or shower waste, where would they go? It would not be like a pipe coming up inside a wall out of sight. But who knows, maybe the little munchies can track through the tile grout out of sight to reach the wall.
Gremlin Ps. Check out a gadjet "Studor Vent", I think, that can eliminate those ugly stink pipes that go up the wall to above the roof.

Why the fear of termites? There are many physical barriers on the market for penetrations that carry +25 year warranties. (stainless mess or Kordon type barriers etc) It appears you are willing to go to an awful amount of trouble at potentially the expense of your plumbing and risk smells, pipework thats impossible to clean with potential steps in your flooring to deal with raised plumbing. The BCA doesnt say you need floor wastes unless its a second floor bathroom or laundry so no problems for you there.
regards

Andrew

Termimesh (stainless fine mesh screen) is around $50 a penetration installed and very easy for concretor/plumber to work with. If you punch holes in your wall then run your plumbing underground all you're really doing is giving the little bastards a potential hide to build mud tubes.

You are probably right wrt plumbing penetrations - it really isn't worth the bother and cost. However perimeter barriers are another matter - expect to spend several thousand bucks if you want to run termimesh around the edge of your slab. This is completely avoidable with the right edge detail.

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Bruce
Draftie

Correct. 75mm of exposed slab edge and a bit of attention to detail every couple of months is money well saved.