Comprehensive Joist & Foundation Calculator

Building & Load Details
feet
feet
PSF
PSF
Lumber & Design Parameters
psi
psi (base)
psi (base)
(LL)
Joist Details & Calculation Mode
in

Select one calculation mode:

feet
lb/ft² (LL)
lbs (Center LL)

Joist Capacity Results ()

Allowable Span: -- ft

Allowable Uniform LL: -- PSF

Allowable Point LL: -- lbs

Input Live Load (LL): -- PSF

Comparison based on calculated PSF.
Joist End Connection Details
lb/screw

Joist End Connection Safety

Enter all required inputs to calculate connection safety.

Skid / Beam Details & Layout Options

Segment Capacity Inputs:

in³
in⁴
feet

Layout Options Inputs:

(Total Load)
(x Demand)
$/post (Est.)

Skid/Beam Analysis

Allowable Load / Segment: -- lbs

Total Bldg Load Demand: -- lbs

Skid Layout Options (Flat)
RankSkidsPostsSegm.SpanSizeTotal Cap. (lbs)Cost (Est.)Eff.
Beam & Post Layout Options (On Edge)
RankBeamsPostsSegm.SpanSizeTotal Cap. (lbs)Cost (Est.)Eff.

Segment load uses current E/Fb/S/I, Skid Span, & Skid Deflection Limit. Layouts use the current E, Fb, & Skid Deflection Limit, building L x W for demand, base S/I for the specific member size, derived segment spans, and require Total Capacity ≥ 1.5x Demand (Factor adjustable above). Layouts are **ranked by lowest estimated Total Cost** (including members and posts) among those meeting the requirement. Eff. = Est. Total Cost / Total Capacity (lower is better value, but does not determine rank).

Notes & Assumptions

  • Calculations update automatically. Values preset by 'Building Type' or 'Lumber Material' can be manually overridden.
  • **Lumber/Design Values:** E, Fb, Fv are initially set based on selections (*verify locally*). Manual edits to E/Fb apply to relevant calculations. Base S & I values corresponding to member size are used where appropriate (e.g., layout calcs). Manual S/I edits apply only to the *Segment Load* calculation for the currently selected Skid/Beam Member. Fb/Fv adjustment factors (CF, Cr=1.15, etc.) applied internally for joists where appropriate. Assumes dry use, normal temp, lateral support unless 'Wet Service' selected for connections.
  • **Joist Calcs:** Use Joist Size properties (strong axis). Joist Deflection limit (L/xxx) applies to Live Load. Uses input LL & DL. Calculates allowable metrics based on selected "Calculate By" mode. Comparison checks calculated allowable LL PSF against the *current* LL PSF input.
  • **Connection Calcs:** Uses effective joist span from Joist Calc, Joist Spacing, LL, DL to find load per end. Compares factored load (LSD: 1.25D+1.5L) and unfactored load (ASD equiv.) to adjusted screw resistance. Wet service reduces screw capacity (Cm=0.67). SF ≥ 1.0 required.
  • **Skid/Beam Calcs:**
    • *Segment Load:* Calculated using the input Skid/Beam Span, Skid Deflection Limit, and the current (potentially edited) E, Fb, **S, and I** values from the Skid/Beam Details section. Deflection check uses *Total Load* (LL+DL) approximation for simplicity.
    • *Layout Options:* Use building L x W and Total Load (LL+DL) for demand. Capacity derived from the *current* E & Fb, the *current* Skid Deflection Limit, the ***base*** S/I of potential members, and spans derived from building length. Requires Total Capacity ≥ [Factor]x Demand (factor is adjustable). Ranked by lowest total estimated cost (members + posts) among valid options.
  • **Cost Estimates:** Lumber costs are rough estimates per 8ft length. Post cost is per post. Actual costs vary significantly by location, length, and supplier. Use for relative comparison only.
  • **Disclaimer:** For estimation and planning only. Consult official span tables, engineering standards (NDS), manufacturer data (screws), and local building codes for final design. Professional consultation recommended.