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Services | Surveying
and Layout | Excavation
| Footings/Foundation
| Foundation
Options | >>Subrough
Plumbing & HVAC | Dampproofing,
Waterproofing and Window Wells | Water
and Sewer Laterals | Foundation
Drain, Backfill and Rough Grade |
Basement Slab
The sub rough
plumbing is located under the basement floor on a
basement foundation, and under the slab on a slab
on grade foundation. Depending on the foundation,
the sub-rough plumbing takes place at different stages
(see
Foundation options ).
Sub-rough plumbing-
After the foundation walls are poured, the DWV pipe
is installed. The plumber digs trenches for the pipes.
He digs under the footings to put the main Drain pipe.
The pipes are placed below the slab according to the
location of the plumbing fixture. Residential plans
usually don't show a plumbing schematic. The pipes
are placed high enough so that they are above the
finished slab. The pipes are leak tested by filling
them up with air or water. After the leak test, the
pipes are covered with sand. The sand protects the
pipes from punctures.
Like
the plumbing pipes, the installer digs trenches for
the ductwork (if forced air is used). The ductwork
is inspected and then covered with sand for protection.
The heat registers coming from the floor is more efficient
than coming from above. However, it is still more
common to put the registers in the ceiling in basement
foundations. If the registers are placed under the
slab you will need a downdraft furnace for the basement
heating and updraft furnace for the main floor. Such
an arrangement creates a better heating system but
is more expensive.
The sub-rough plumbing
and HVAC takes place at different times in the project
depending on the type of foundation.
With a basement foundation
the sub-rough work begins as soon as the foundation
wall forms are stripped. Once both systems are installed,
tested, inspected and covered the floor slab is poured.
When a slab on grade
is poured the sub-rough work must go in before the
slab is poured the same as a basement foundation.
When the floor and
foundation is poured in one pour as it is often done
in the Southwest, the sub-rough work is installed
after the foundation is formed. It also should be
noted that because areas where monolithic pours are
popular the HVAC is not often placed in the slab.
One reason is it is generally cheaper to put the HVAC
system in the attic space. The other reason is that
Air conditioning which is used heavily is more efficient
blowing down from the ceiling.
The water supply lateral is also installed as part
of the sub-rough plumbing for monolithic foundations
The work on the under
floor plumbing and HVAC can begin before or after
the floor system is framed. It is generally best to
have the plumbers and HVAC put in after the stem wall
is poured. At this stage each trade installs the main
drain lines and trunk lines. After the floor and the
rest of the house is framed, they can return to complete
the rough-in.
Where slab floor
are used, radiant floor heating is a popular heating
system. Pipes carrying hot water run through the slab.
The heat is transferred to the slab which radiates
through the home. Radiant floor heat is a comfortable
and efficient heating system. It costs more than a
typical forced air system but many people believe
that it is worth it.
When installing a radiant floor system the plumbing
is installed first. Rigid insulation board is laid
on top of the ground, followed by the radiant floor
pipe. The system is tested and then covered with the
concrete floor slab. Most installers recommend that
the pipes remain under pressure during the slab pour
so that damage to pipes can be detected and repaired.
It is critical that
placement of the under slab plumbing and heating is
accurate. It is possible to make changes by cutting
the concrete but that is expensive. If radiant floor
heating is used, it would be difficult to change the
sub-rough plumbing below with out major expense to
the in floor heating system. It takes about a day
each for the sub-rough plumbing and heating.
