Notching and Drilling Joists Holes should be drilled or notched in accordance with BS6700, BS5449 and NHBC regulations. For plumbing installations Uponor prefer the use of drilling over notching for the following reasons: • Improved health and safety because the installer can install pipes from below rather than work on open joists; holes for pipes can be drilled after the floor boards have been laid. • Larger pipe sizes can be accommodated by drilling (0.25 x joist depth) as opposed to notching (0.125 x joist depth). • No risk of damaging the pipes when the floor boards are fixed down. • Thermal insulation can be more easily applied and accommodated.
The following is an accepted guide to avoid potential structural problems in domestic floors. Any notching or drilling outside of the permitted zones must be subject to structural calculations by a structural engineer to verify suitability. Joists can be weakened and become structurally unsound by: holes drilled off the centre line or near to the end of a joist, holes or notches made too close together and, notching too close to the centre of the joist span. Prior to installing the plumbing pipe work attention should be given to planning the pipe routes to ensure that any holes/ notches are within the permitted zones shown below.
Notching Zone Example With a joist span of 3.5 metres between load bearing walls and joist depth of 225mm, the notching zone is:
Drilling Zone Example With a joist span of 3.5 metres between load bearing walls and joist depth of 225mm, the drilling zone is:
Between 0.7 x 3.5 and 0.25 x 3.5 = 0.245 to 0.875 metres from each wall.
Between 0.25 x 3.5 and 0.4 x 3.5 = 0.875 to 1.4 metres from each wall.
The permitted maximum depth of notch is: 0.125 x 225 = 28mm
The permitted maximum diameter of hole is: 0.25 x 225 = 56mm
Notching
Drilling
TTED ZONES OTCHING
PERMITTED ZONES FOR DRILLING
PERMITTED ZONES 5FOR NOTCHING 5 2 . 0.2 x0 nx an a p p S S x x an an p S 07 Sp 07 0. 0.
an
Sp
an
Sp
x
0.4
PERMITTED ZONES FOR DRILLING
nx
a Sp
x an Sp 5 0.2
Centre Line
C
x an Sp 5 0.2
CL
an
an
an
Sp
Sp
0.25 x Depth
Engineered Joists The flexibility of Uponor MLC pipe makes it ideally suited for cabling through knock-outs in the webbing of proprietary timber I beams, such as TJI joists used in silent floor systems.
0.4
C
Sp 0.25 x Depth
At st a Le D 3x
Holes mustAetast L be at least 3 dia 3 x D be a (centre to centre) (cent apart and no holes must apart and no be within 4” (105mm) of a notch. be within 4” (105mm
The form stability of the MLC pipe prevents it from sagging between joists when hot water is circulating, which is a tendency with standard plastic piping systems.
Uponor MLC Press-fit Technical Guide l 65