concrete slab reference material

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Fulthrotl said:
if the pipes don't come up in the walls, you won't make any money.

any questions?
Click to expand...

.....gee thanks


I have been researching on my own but I figured it couldn't hurt to ask my peers here. I find this forum informative.

Found some research about laying out a right angle with string. Don't take the measurements off the electrical drawings. Don't trust the plumbers measurements. The GC could provide you with a definitive line that all trades can go off of.

When tile is being used, I find using a small sonna tube with sand in it allows for some play. If wrong just scoop out some sand and add concrete. The tile hides it.

Checking the "Americian Electricians handbook" to see if there's any info there.
 
JJWalecka said:
.....gee thanks
I have been researching on my own but I figured it couldn't hurt to ask my peers here. I find this forum informative.
Click to expand...

i was being a smartass... sorry... :angel:

i've got a 3,000 sq ft slab on grade wood
framed office coming up. it has about 5,500
ft of 3/4" pipe in the slab. open beam
ceilings, pain to pipe, etc.

here's what i've found rocks over the years:

basic rules....

no plastic penetrations thru the slab

scotchwrap 20 mil all GRC penetrations

instead of 90's and nipples, use yard ells.

GRC couplings on all stubs up NO BARE THREADS

use all FA plastic adapters, with a close nipple
instead of a MA. MA"s break too easily

long chase nipples and FA's are an excellent way to
hit a box with pvc. makes nice pulling.

use plastic threaded plugs on those stubbed up
nipples with GRC couplings. it's worth the money.
one pipe full of concrete makes those plugs seem cheap

put pull string in conduit before pour. leave 10' extra on
each end, stuff it in the pipe, and put a pipe plug on it.
later on, when you extend the stub to a box with flex,
you will have enough string.

if you have to splice a string, pull it all the way thru
the pipe. anyone leaving knots in 125 lb pull string in
an underground conduit should be shot.

get the autocad file of the floorplan. you can lay out
every single pipe on it easily, and make your own
control lines so you know exactly where to put everything.
i did the layout for the largest hospital in calif all in autocad.
the building was curved and a block long, and laid out on a
260' 4" or some silly radius from a point in the parking lot.
there were eight parallell and square pieces of steel in the
structure, and i'm sure that was by accident. think spokes of
a wheel.

you can do stubs and stuff and make up control lines to stuff
you can find in the real world.

hit outside walls and plumbing walls whenever possible.
they are fast to lay out, and if a plumber lays out a wet
wall wrong, they move the wall. if a sparky lays out a
wall wrong, the sparky moves.

blow pipe to get string in before pouring. this clears
dirt from the pipes and makes sure everything is
connected quickly. you can also use a shop vac to suck
the string in

this slab i'm doing with 125ish home runs, i'm hitting
most of them around the perimeter of the building, and
flexing up the partition walls. so what i'm doing to get all
the conduits up, instead of driving 1/2" emt stakes, i am
putting 7/8" strut the length of the building on two sides
3" below finished floor, and strapping the stubs to it with
strut straps. the 7/8" strut is being held off the form the
length of a 1/2" pvc coupling, with a 4" X 1/4"-20 bolt
and fender washers every 5' to support it, drilled thru the
form. it's 250' of strut, and will support about 150' stubs,
and it's fast to do... about $400 in strut.

most of them are data conduits. i can pre wrap and
make up the yard ells, put the two runs of strut on
the form, mark where my stubs are at on them, and
rock. i'm allowing two days to do the entire slab by
myself.

i've got 70 stubs coming up on a telephone backboard
in the middle of the slab... two 7/8" strut back to back,
laid out in autocad so they come up exactly where they
are supposed to, and use three form stakes you steal
from the forming contractor, driving them below the
slab level and bolting them to the strut, so the top edge
of the strut is 3" below finish floor.

pvc floats. if you aren't under the visqueen, stake
it or tie wire it.

put in several pipes just for grins. they are called
spares, but they aren't. they are invaluable requirements.

don't use 1/2" pipe in a slab. just. don't.

always wear gloves when handling PVC. always.
the greasy film that covers old pvc is polyvinyl chloride,
leached out of the plastic. new pipe isn't as bad, but the
stuff is absorbed thru the skin, and causes cancer.

on pour day, be there with rubber boots on, and
don't leave till they are running the power finishers
over the surface.
 
Last edited:
Fulthrotl said:
i was being a smartass... sorry... :angel

instead of 90's and nipples, use yard ells.
Click to expand...

So was I :p

Pardon my ignorance but what's a yard ell. Trade name out on that coast?

New some stuff but overall, freakin great info thanks a bunch.

The autocad sounds great if I had the means to do it.
 
A cheap and effective cap on 3/4" rigid stub ups is 2 liter Coke bottle caps. They thread right on and can be used over and over.


Another trick I use if I have a lot of floor boxes is to pack them with wet sand. This keeps the concrete slurry out of them and can be removed quickly with a shop vac.
 
JJWalecka said:
So was I :p

Pardon my ignorance but what's a yard ell. Trade name out on that coast?

New some stuff but overall, freakin great info thanks a bunch.

The autocad sounds great if I had the means to do it.
Click to expand...

just a GRC factory 90 with a long side on it... saves buying a coupling
and a 4" or 6" nipple for each stub, screwing it together, etc.

autocad LT is all you need for most of what we do as sparkies.....
asbuilts, quickie drawings, etc. most construction is a two dimensional
plan system.

that is changing. autocad revit does building information, and does
the whole thing in 3 dimensions, and interference between building
elements can be caught.... radiuses of conduit bends, all of that is
shown actual size in the drawing, not just symbolically.

i dropped off the signed contract with the general today, and explained
how i planned on doing the slab, mentioning that total number of conduits
in this little building will probably be about 125 in the slab.... he just looked
at me, said "what?", and his eyes sorta glazed over..... it's an awful lot for a
little wood framed office building....:happysad:

Leitz has a layout laser that you can load a drawing into, and it'll project all
the points on a layout onto a surface, with 1/8" accuracy... designed for plumbers
and electricians, and field survey guys mapping a building for builder to draw
remodel plans.... you can project datum points, or map points, either one.

it's a little bit expensive unless you have a huge need for accurate layouts....

for most of us, a string and a laser get it all done.
 
Fulthrotl said:
just a GRC factory 90 with a long side on it... saves buying a coupling
and a 4" or 6" nipple for each stub, screwing it together, etc.

autocad LT is all you need for most of what we do as sparkies.....
asbuilts, quickie drawings, etc. most construction is a two dimensional
plan system.

that is changing. autocad revit does building information, and does
the whole thing in 3 dimensions, and interference between building
elements can be caught.... radiuses of conduit bends, all of that is
shown actual size in the drawing, not just symbolically.

i dropped off the signed contract with the general today, and explained
how i planned on doing the slab, mentioning that total number of conduits
in this little building will probably be about 125 in the slab.... he just looked
at me, said "what?", and his eyes sorta glazed over..... it's an awful lot for a
little wood framed office building....:happysad:

Leitz has a layout laser that you can load a drawing into, and it'll project all
the points on a layout onto a surface, with 1/8" accuracy... designed for plumbers
and electricians, and field survey guys mapping a building for builder to draw
remodel plans.... you can project datum points, or map points, either one.

it's a little bit expensive unless you have a huge need for accurate layouts....

for most of us, a string and a laser get it all done.
Click to expand...

Thanks man. Appreciate the info
 
I agree with everything Fulthrottl said.

We ALWAYS use rigid or fiberglass 90's under concrete no matter how small the conduit is.

ALWAYS PUT COUPLINGS ON YOUR RIGID STUBUPS, NO BARE THREADS!

We use a lot of strut in the concrete/ground to help rack conduits. Well worth the cost to keep conduits plumb! Sometimes I'll drive scrap pieces of conduit into the ground and strap it to the strut to help brace the strut. I like deep better than shallow, a lot less deflection.

I try to use ZERO couplings underground! I want that pipe to leave an FA on one stubup and hit an FA on another stubup. It should be no problem using bells only.

I like to premake all my rigid 90's with nipples couplings duct tape FA's on them. Then glue a 10' stick into them so it has time to setup. I find FA's are pretty loose if you glue on the fly sometimes the pipe will try to work itself out of the joint if you're not careful.
 
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