Pvc in cement pour

[smallfish]

Do you see any problem in running 1" pvc tied ontop of the metal wire grid upon which 4" of concrete is poured, making the floor of a building?

Table 300.5 allows a zero minimum cover requirement for nonmetallic raceways "under a building".
Pvc in the cement pour is not quite under the building, so I wonder could it be allowed?
Thanks

 

[mgookin]

Are you saying the 1" pvc is horizontal, parallel to, and laying on top of 6"x6" welded wire fabric reinforcement?

If so, the reinforcement needs to maintain a minimum concrete cover and the pvc, technically, is violating that. But how much are we talking about?

 

[smallfish]

the 1" pvc is laying on top of the 6"x6" welded wire fabric reinforcement and runs horizontal to it, effectively 3 " below the top of the poured floor.

 

[cadpoint]

Fish it below the wire mesh, most times they will cut the expansion joints deep and will
cut you pipe in half.

 

[gadfly56]

Fish it below the wire mesh, most times they will cut the expansion joints deep and will
cut you pipe in half.

Excellent point! Unless the control joints are cast in.

 

[infinity]

Do you see any problem in running 1" pvc tied ontop of the metal wire grid upon which 4" of concrete is poured, making the floor of a building?

Table 300.5 allows a zero minimum cover requirement for nonmetallic raceways "under a building".
Pvc in the cement pour is not quite under the building, so I wonder could it be allowed?
Thanks

NEC wise you could run in 1/4" below the finished surface if you want. What might happen to it is another issue.

 

[brichter]

Wire mesh usually gets lifted from the sub-surface to embed it in the concrete.

 

[curt swartz]

Wire mesh usually gets lifted from the sub-surface to embed it in the concrete.

I agree, the mesh gets lifted during the pour. Putting your pipe on top of the mesh will create a big problem for you and the concrete contractor.

 

[mgookin]

Do you see any problem in running 1" pvc tied ontop of the metal wire grid upon which 4" of concrete is poured, making the floor of a building?

Table 300.5 allows a zero minimum cover requirement for nonmetallic raceways "under a building".
Pvc in the cement pour is not quite under the building, so I wonder could it be allowed?
Thanks

At first I thought you were on an elevated deck. But now I read it again....


Are you on ground floor or on the 30th story of a high rise?

 

[smallfish]

Nec wise you could run it a 1/4" below the surface (from post 6).
Please refer me to the code article or whereabouts that this is stated.
Thanks

 

[infinity]

Nec wise you could run it a 1/4" below the surface (from post 6).
Please refer me to the code article or whereabouts that this is stated.
Thanks

It's not, the 1/4" was just an arbitrary number. In poured concrete there is no minimum cover depth for the raceway in the concrete required by the NEC. You mentioned T300.5 which is not applicable. Sorry for the confusion.

 

[hardworkingstiff]

If you are on top of the wire and the wire is 3" down, the top of the 1" conduit will be less than 2" from the surface. I bet the concrete above the conduit will develop a crack following the conduit within a week.

I've always wondered if the building slab was part of the building. The reason is that Table 300.5 states 0" of cover when UNDER the building. So, if the slab is part of the building, then wouldn't you have to under the slab to be under the building? I've never had to deal with this on an inspection because I've always dug a 2" deep trench so the concrete guys won't have to trip or kick my conduits.

IMO, you should try to get the conduit under the reinforcement wire.

 

[Fulthrotl]

Do you see any problem in running 1" pvc tied ontop of the metal wire grid upon which 4" of concrete is poured, making the floor of a building?

yeah, i do. if you put it under the mesh, you won't have any problems.

you put it on top of the mesh, and you are going to hate your life.
everyone connected with the building will hate your life, too. :happyyes:

so, put the pvc in BEFORE they spread the mesh. the mesh will hold it down,
and when they use hooks to lift the mesh during the pour, you won't have
pvc coming out of the slab. unless it's tied EVERYWHERE, it's gonna float,
and if it's that close to the surface, the concrete will get spider cracks where
it's close.

and rest assured when they score the slab with expansion cracks, they will
cut every single piece of pipe, and you'll have water/concrete slurry going
into every single piece of pipe.

if you do decide to put it on top of the mat, be sure to pull wire before the
pour, if at all possible, so the wire will get cut when they score the slab as well.