Design of floor joists in a domestic building

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Discussion Overview

The discussion revolves around the design of floor joists in a domestic building, specifically focusing on structural requirements for a span of 3.0 meters between walls. Participants explore the necessary calculations and considerations, including material properties, loading conditions, and compliance with local building codes.

Discussion Character

  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant requests help with the design parameters, including dimensions, material properties, and deflection limits.
  • Another participant emphasizes the importance of local building codes and suggests that a licensed engineer should perform the calculations.
  • Questions are raised about whether the inquiry is for homework, with a suggestion that accurate results depend on knowledge of local regulations.
  • A participant expresses concern about providing advice without knowing if it complies with building codes, indicating a potential ethical issue in self-engineering.
  • The original poster clarifies that the inquiry is for a college assignment and seeks assistance with the design process.
  • Another participant requests additional information, such as the density of materials and live load specifications, to assist with the calculations.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of adhering to local building codes and the importance of professional guidance for structural design. However, there is no consensus on how to proceed with the calculations without further information about material densities and loading conditions.

Contextual Notes

Limitations include the lack of specific local building codes, material densities, and live load requirements, which are essential for accurate structural design.

Who May Find This Useful

This discussion may be useful for students studying structural engineering, professionals seeking to understand residential design requirements, and individuals interested in the ethical considerations of self-engineering.

john paul jr
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Could i have some help with the following:

Design, floor joists in a domestic building to span between walls 3.0m apart.

the construction of the floor is
18mm timber boards
joists
15mm overall plasterboard + skim coat

The joists are 50mm wide and at 450mm centres
The permissible stress in the timber is 5.3N/mm(squared) and the elstic modulus of the timber is 8000N/mm(squared)
the deflection must be limited at 0.3% of the span.
 
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john paul jr said:
Could i have some help with the following:

Design, floor joists in a domestic building to span between walls 3.0m apart.

the construction of the floor is
18mm timber boards
joists
15mm overall plasterboard + skim coat

The joists are 50mm wide and at 450mm centres
The permissible stress in the timber is 5.3N/mm(squared) and the elstic modulus of the timber is 8000N/mm(squared)
the deflection must be limited at 0.3% of the span.

What is your background? What city is this in? What are the local codes regarding this kind of construction? You need a licensed engineer to make those calculations for you -- one who is familiar with your municipality's building codes and inspectors.
 
Is this homework? If not, there's not much of a chance for getting an accurate result without knowing local building codes.
 
Even if we had a PE structural engineer as a member or on staff, we wouldn't condone giving such advice since we can't be sure this isn't a code violation (a homeowner trying to do his own structural engineering).
 
Thanks for getting back to me this is actually a college assignment that I've been stuck on for quite a while that i needed help on for designing the floor joists.
 
Ok so is a college assignment. Start off by showing your work, so we can know with what you are having problems.
 
john paul jr: Do you have the density of the timber boards, and of the joist material? Do you have the density of plasterboard? Do you have the floor applied live load per unit area?
 

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