Styro Block Construction Wiring

[shed69]

Hi guys and gals

I've just won 4 new build installations which is the styroblock polystyrene type stuff.... Its already up to 1st floor and therefore concrete has been poured in..... Has anyone any experience of wiring these and if so what tool did you use to channel out and cut in boxes? I've looked on google etc and seen some of the hot guns but I would like some advice off anyone that has dealt with this before.......Any info would be helpful......

 

[ProDave]

Surely you don't directly bury the cable in polystyrene? (Sory Styrofoam is what the yanks call it)

you do know what polystyrene does to PVC?

Is there not some form of battening out to give a service void then plasterboard or something?

If it really is going straight into polystyrene then I think steel conduit or micc is the only way. I wouldn't even be happy with PVC conduit.

 

[kerching]

+1 to what my learned colleague above has said

Polystyrene is not a friend of PVC as it causes migration of the plasiciser

 

[OnOff]

522.5.3?

Presumably then you couldn't even put the cabling in PVC conduit?

Nice bit'o galv tube and singles then!  :lol:

 

[stuartrw79]

Sorry no experience of these.... Just out of interest you say you won the tender to wire the 4 ... what have you quoted for  ????

 

[ProDave]

Sorry no experience of these.... Just out of interest you say you won the tender to wire the 4 ... what have you quoted for  ????

Everybody else quoted for galv conduit or pyro, he quoted for t&e clipped direct.

I do hope not.

 

[batty]

Very strange getting a contract without knowing how to wire it.

 

[shed69]

HI all

Mixed comments as per the norm i see!

Firstly as per the norm with this builder we came in at a late stage (I've done around 30 flats for this particular guy and don't have competition for work now regards price etc as he knows we do the job right etc, however , this is the first time they have done styroblock and they have cracked on and built the first level and filled with concrete pretty much before we had chance to even think about the logistics so its a bit of a pain.....

Secondly, yes we're aware off the pvc/polystyrene effect, thanks Dave......!

I visited site and asked the question of "will the plasteredboard be battened out" - "No, its will be fixed straight to the styrofoam"

So, I leave site with my thoughts to myself firstly before raising concerns ( I haven't started any wiring yet and its a good few weeks away so if it can't be done how I'm happy to do it then it won't be done by me) I am now looking into the potential problems, hence the topic, and wanted to know what people have used to chop/channel in the boxes etc, I have in the meantime come across a hot gun with various blades so that should suffice I think.....

So to follow up, I need them to batten off the styrofoam (not negotiable) but from the comments are there concerns in dropping wires down to boxes??? I was thinking of either leaving loose from ceiling or a few fixings to hold - now I'm not so sure.......

 

[steptoe]

how thick/deep is the polystyrene?

possibly cut out a 35mm strip and clip some 20mm round conduit in the middle so its not touching the polystyrene, maybe a bit of expanding foam to hold it in place/re-instate the insulation properties,,,,,   :C

 

[ProDave]

If these are what I think they are, the polystyrene (I refuse to speak like a yank) is the main insulation in the building. So if you channel too much out, you are compromising the insulation.  Surely with modern building regs that won't be allowed.

I think what's needed (based on my working on eco homess) is to cover the polystyrene with some form of membrane, one of the many building fabrics, then batten it with say 25 by 50mm battens. That would protect the cable and give a void to run services without compromising the insulation.

Is the building spec so tight, that the rooms are so small they would really miss 25mm of each outside wall? (probably less than that as they will lose a bit anyway if they dot and dab the plasterboard) 

 

[wozz]

I was thinking some sort of membrane like dave although I have no experience of these.

Is battening really a option what would it fix to? Dot and dab seems easier to me from a building pov.

 

[ProDave]

What do the makers of these blocks recommend? this must be an issue faced by anyone using them, so there must be standard solutions.

 

[Steve3948]

The one and only we did, all walls had a render scratch coat 5-10mm to which we boxed and channelled as normal.

If no render you could staple a 150mm DPC vertical at each drop and channel down that and dry line boxes, just a thought.

 

[shed69]

Good call Dave/Steve, membrane down each drop or even in a chase if their adamant they don't wanna batten it out, this alleviates the pvc touching the polystyrene (For Daves sake!!!!).......... I'm assuming that as long as there is no direct bare back (ooh er missis) touching that it will suffice

Steps - not sure about pvc conduit, its pvc still and don't know if it will be a future problem....???? It was one of my 1st thoughts to use YT2 before the builder said they wanted to fix plasterboard direct to polystyrene......

Dave - Not sure about recommended, Ive seen capping directly over this on internet but now not happy with it touching at all, (following the membrane idea its an easy option to staple)

Good thoughts tho guys and certainly helping......

 

[steptoe]

shed, that was why I suggested expanding foam, to keep the conduit away from the polystyrene.

still, i think Dave has a LOT more experience on this sort of stuff than I do,

I'd be following his advice if I were me.

 

[sparks2911]

Personnaly i would speak to tech department of Napit, NICEIC etc and maybe get their take on it. hth

 

[wozz]

id speak to the manuf of the walls to see if there is a problem or if its chemically different to other polystyrene.

 

[kerching]

Never gave it much thought really, THEN a little light came on in my deepest darkest recesses of my frontal lobe.

When I was a little sparkler I had a model workshop which had a lathe, milling machine in it....all battery powered. The material supplied was Styrofoam ....so I goooooooooooggggglied it

Styrofoam is a trademarked brand of closed-cell extruded polystyrene foam currently made for thermal insulation and craft applications. It is owned and manufactured by The Dow Chemical Company.[1]

In the United States and Canada, the word styrofoam refers to expanded (not extruded) polystyrene foam, such as disposable coffee cups, coolers, or cushioning material in packaging, which are typically white and are made of expanded polystyrene beads.[1] This is a different material from the extruded polystyrene used for Styrofoam insulation. The polystyrene foam used for craft applications, which can be identified by its roughness and by the fact that it "crunches" when cut, is moderately soluble in many organic solvents, cyanoacrylate, and the propellants and solvents of spray paint, and is not specifically identified as expanded or extruded. Another tradename for expanded polystyrene is thermacol, originated by BASF.

So we may be barking up the wrong un

Just researching....

 

[OnOff]

Pretty sure I've read somewhere............maybe a US site............that they cut channels into some of these foam walls, fit the cable and then "gun foam"  directly on/over the cable to secure it and maintain the insulation properties. Can't think where I've seen it though.

 

[shed69]

I will speak with them Monday to find out exactly....

I too have today seen channel cut and cables foamed in....???

Have to be 100% though.....