Roughing in electrical/plumbing in slab

[Ashes]

Hopefully a question the sparkies and plumbers can answer quickly. I haven't done this before so not sure of the answer.

I'm probably 4 or 5 weeks away from putting the slab down for my shed. I'd like to have the electric conduit and water/drain run through the slab instead of through the wall. I haven't organised a sparky or plumber as yet.

Who would normally organise the putting in of the conduit/drains when the slab is being formed up or poured? Who do I need to organise and when for this work to be done?

I'm looking to have conduit run in for electricity. 2 or 3 in floor mounted powerpoints (in the middle of the workarea with covers). Looking to run mains water in and a drain for a sink going out.

[journeyman Mick]

Usually roughed in by the plumber/sparky who is doing the rest of the job. I'd be wary about running the water supply in the slab, avoid it unless the water needs to come out of the floor well away from any walls. I've seen literally 100's of places that were built in teh 70s and 80s where in slab water pipes have started leaking and have had to be replaced with retrofitted pipes. All the newer places have minimal supply lines in the slab (avoided unless absolutely neccesary). They are run in the ceiling and down inside wall cavitys instead. Where they are run through the slab both hot and cold lines must be in lagged copper to prevent the movement of the pipes rubbing holes in the pipes.

Mick

[Honorary Bloke]

What Mick said. They ran plumbing through the slab for dog's ages and now they are reaping the whirlwind. Modern practice is to run in the ceiling and drop to needed locations.

A couple of electrical outlets in the floor might be a good idea, though. Your sparky will know what conduit to run.

[wonderplumb]

It can be done, though not desirable. If you must do it this way, try to scratch it in the soil under the slab, try to do it in one continuous length with no joins, have your turn up done with a pulled bend rather that a soldered one and make sure its lagged.

[Ashes]

The water/drain access is actually at the rear of the shed and won't be seen so I might just take the easier option of running the water and drain through the wall.

Does the sparky come in before/after it is formed up. Guessing before if any trenching is required for cables?

So you'd suggest I start getting some sparky quotes now and lining one up. I think I might have an interesting mains cable run as my meter box is at the front of a 2 story home, and the shed is at the back of the yard. Probably a 30m run with a house in the way!

[DJ’s Timber]

Do you have access under the house? My cables were run under the house to the nearest point to the shed then in to a trench as shown here, but if your on a slab then you'll have to go in a trench all the way around the house .

[Honorary Bloke]

Does the sparky come in before/after it is formed up. Guessing before if any trenching is required for cables?

Yes. Before.

So you'd suggest I start getting some sparky quotes now and lining one up. I think I might have an interesting mains cable run as my meter box is at the front of a 2 story home, and the shed is at the back of the yard. Probably a 30m run with a house in the way!

I'd like to see a pic of that! I just can't visualise it. Doesn't the power come from the street to a meter box on your house?

[rod1949]

I'd be incline to also bring the power down rather than up.

[Ashes]

A picture is worth a 1000 words...Looks like the best option is to dig a trench down the sideway (on the side the fuse box is). Under about 3m of pavers (big ones so hopefully can get away with pulling up just a few..Under the garden bed next to the pavers, avoiding the sprinkler system..across the back lawn (avoiding the main water line running to a tap and then into the shed. Probably a sewer line in the way as well...

The house is on a slab, so can't go under. It is a 2 story house so probably difficult running it in the ceiling

[wdyte_dan]

It is definitely easier to put the plumbing and electrics in prior to concrete, plumbing in particular in your case will be a major hassle post pour if it's not done right.

The only thing to consider is that there are Australian Standards to meet in terms of electrical and plumbing installations below ground, and it might pay to involve those who deal in the black arts/protected trades of electricity and plumbing to advise you early on how to do these things.

You have come up with a pretty good plan on your other thread, print it and give it to a sparky/plumber and ask them to advise on installing services. They may be comfortable with you doing a certain amount of the labour/installation as part of the job they will sign off, although some (esp sparkies) may not be as comfortable.

The plumbing could be about 90% done before your even poor the slab. The sparkies job will likey be easier as there is probably only going to be one entry point to the shed - if this is through the slab, you'll need to check with him to install the appriopriate conduit rising near the switchbox (Do you still want those in-floor power points?) Anyway, consult early!

[dan76]

mate , talk to the tradies and with the attitude you have of being planned out and having a clear idea of what you want the finished job to be i cant see you having any problems.

except maybe the prices lol

[patty]

The conduit on the inside of the wall is simple you just have to compensate for your wall/purling thickness on the slab and offset your conduit to be just on the outside of it.
Instead of having floor mounted Gpo's which sometimes are practical but sometimes they just end up being in the wrong spot, I would tend to go for suspended pendant type gpos on jack chain!

[Ashes]

Was speaking to my shed installer today just letting them know that they sent me an old version of the owner builder which caused my application to be rejected...

anyways..

they recommend that normally power conduit is run up next to the slab and up one of the ridges in the colorbond. Reasoning being that conduit in the slab weakens it. Same goes for mains water in. They recommend drain water be run out through the wall for the same reason as well..

does that sound right? If so, takes away the compexity of having to co-ordinate sparky, plumber and concreter

[rod1949]

... Reasoning being that conduit in the slab weakens it.

What a load of Cocky poo.

[silentC]

People with showers and toilets on concrete slabs are in trouble then. If a 25mm conduit weakens a slab, imagine what a 100mm poo pipe would do.