How to use this calculator
- Pick the actual member size. Choose a dressed 2x size or enter the measured width and depth.
- Enter span and line load. Use the simple span plus total live and dead line load carried by the member.
- Locate and size the notch. Enter the notch station from one support and the depth removed from the member.
- Enter design limits. Replace the example Fb, Fv and max notch-depth ratio with project-specific values.
- Read the governing utilization. Review whether net-section bending, net-section shear or the entered notch ratio controls.
How it works
This notched joist capacity calculator treats the member as a simple-span
rectangular beam under uniform line load. It first reduces the full depth
d by the notch depth a:
d_net = d - a
The gross and net rectangular section properties are then compared:
S_gross = b*d^2 / 6
S_net = b*d_net^2 / 6
I_gross = b*d^3 / 12
I_net = b*d_net^3 / 12
For uniform line load w and span L, the support
reaction is R = w*L/2. At the notch station x,
the calculator uses:
M_x = R*x - w*x^2/2
V_x = |R - w*x|
fb_net = M_x / S_net
fv_net = 1.5 x V_x / (b x d_net)
It reports utilization from net bending stress, net shear stress and the
entered notch-depth ratio a/d. The largest utilization is the
governing result.
Worked example
Verified against the live calculator
A 2x10 member spanning 12 ft carries
66.7 lb/ft. A 1 in notch at
1 ft from support leaves 8.25 in net depth.
With example values Fb = 1000 psi, Fv = 135 psi
and an entered 16.7% notch ratio screen, the calculator
compares the net-section stresses with the entered limits and shows how
much section modulus was removed.
Frequently asked questions
Is this a code-approved joist notch calculator?
No. It is not a code-approved joist notch calculator; it is an elastic stress and depth-ratio screen for a rectangular member. Adopted building code, design standard, manufacturer instructions, engineered repair details and local inspection control whether a notch is allowed.
What does the calculator check?
It subtracts the notch depth from the full member depth, recomputes rectangular section modulus and area moment of inertia at the notch, then checks bending stress, shear stress and the max notch-depth ratio you enter.
Can I use it for deck joists or floor joists?
You can use it to screen the remaining net section, but deck and floor framing also need span-table limits, bearing, hangers, ledgers, fasteners, holes, lateral restraint, treatment/wet-service factors and permit review where applicable.
Where should I measure notch station?
Enter the distance from one support to the notch critical section. For a symmetric simple span under uniform load, the calculator uses the equivalent nearest-support station for moment and shear.
What should I enter for Fb and Fv?
Use adjusted bending and shear design values from the same adopted design basis for the actual species, grade, size, service condition and load-duration assumptions. The defaults are examples only.
Does this model sistering or reinforcement?
No. Reinforcement, sistered joists, plywood gussets, steel plates, fastener schedules and repair details are separate engineered connection problems.
Method & assumptions
- Simple-span, single rectangular sawn member with uniform line load only.
- Common 2x sizes use dressed North American actual dimensions; custom mode uses the actual dimensions you enter.
- The notch is modeled as a reduced rectangular section with net depth
d - a. - The entered max notch-depth ratio is a user screen, not a built-in code rule.
- Defaults for Fb, Fv and max notch ratio are examples only. Use adjusted values and limits from one consistent design basis.
- Does not check end-notch location rules, tension-side notch prohibitions, holes, splits, bearing, lateral restraint, repetitive-member factors, wet service, load duration, joist hangers, ledgers, fasteners, reinforcement, sistering, repair details, permits or inspection acceptance.
- For unnotched span screening, use the wood beam span calculator or deck joist span calculator. For direct section properties, use the section modulus calculator.