Intro to Timber-Framed residential Building Design

Summary

This video series explores various aspects of timber framing design for residential buildings, focusing on Australian Standard AAS 1684. It covers timber components for structures up to two stories, detailing the differences between cyclonic and non-cyclonic areas. The video explains timber grading methods, including visual and machine grading, and the importance of selecting appropriate timber grades for construction. It concludes with an overview of timber strength classifications and their application in designing timber-framed houses.

Takeaways

• 🏠 The video discusses timber framing design for residential buildings, focusing on Australian Standard AAS 1684.
• 📚 AAS 1684 is divided into four parts, addressing different aspects of timber-framed construction, including non-cyclonic loads and cyclonic areas.
• 🏗️ The standard primarily applies to Class 1 and Class 10 buildings, which include residential dwellings and non-habitable structures.
• 📏 It provides span tables for various timber members needed in a timber-framed house, considering different wind classifications and stress grades.
• 🌳 Milled timber is classified into different grades based on visual or machine grading, which helps designers select the appropriate strength for each member.
• 👀 Visual grading involves a person assessing the timber's defects, knots, grain slope, and assigning a grade based on its strength.
• 🤖 Machine grading assesses timber stiffness and assigns a color-coded grade, with the lowest stiffness value indicating the timber's strength.
• 🔍 The F-grade or MGP grade of timber must be specified by designers to ensure it meets the required strength for the application.
• 📉 Timber species vary in their F-grade values, with hardwoods generally having higher values than softwoods, though exceptions exist.
• 📊 The video includes a table illustrating the range of F values available for different timber species, with hardwoods in the shaded region.
• 🔍 Understanding the F-grade's meaning and its relation to timber strength is crucial, but the derivation process is not necessary for designers to know.

Q & A

What is the Australian standard AAS 1684 related to?

AAS 1684 is an Australian standard related to the design of residential timber-framed construction, covering timber components in buildings up to two storeys high with specific limitations on dimensions and roof pitch.

What happens if a timber component falls outside the limits of AAS 1684?

If a component falls outside the limits of AAS 1684, other Australian standards such as AS 1720 for tender structures or AS 4100 for steel structures might need to be referred to.

How many parts does AAS 1684 consist of, and what do they cover?

AAS 1684 consists of four parts. The first part deals with the derivation of values used in span tables, parts two and four deal with non-cyclonic loads, and part three addresses the design of timber framing in cyclonic areas.

What types of buildings does AAS 1684 primarily deal with?

AAS 1684 primarily deals with Class 1 and Class 10 buildings as defined in the Building Code of Australia, which includes houses and other residential dwellings, as well as non-habitable structures like sheds and carports.

How does AAS 1684 categorize wind classifications for timber framing?

AAS 1684 has different tables for different wind classifications, which are used to design timber framing according to the wind conditions of the area.

What are the two different methods of grading milled timber in Australia?

The two different methods of grading milled timber in Australia are visual grading and machine grading.

How is visually graded timber assessed?

Visually graded timber is assessed by a person who examines the piece of timber for the number of knots, defects, slope of the grain, and how it has been cut, then classifies the grade of the timber accordingly.

What does the stamp on a visually graded timber indicate?

The stamp on a visually graded timber indicates the strength of the timber according to its grade, the grading method (visual or machine), the stress grade, whether it's seasoned or unseasoned, the species, the name of the milling company, and the Australian standard used for grading.

How does machine grading assess the timber's stiffness and strength?

Machine grading involves passing the timber through a machine that bends the timber and assesses its stiffness. The machine squirts a color of paint on the timber to indicate its stiffness, with the lowest value being the stiffness of the timber piece.

What is the significance of the F-grade or MGP grade in timber design?

The F-grade or MGP grade indicates the strength and modulus of elasticity of the timber, which is crucial for a designer to specify the right strength for a particular application in timber framing.

Why is it important to understand the F grade of a timber piece?

Understanding the F grade is important to ensure that the timber used has the appropriate strength for its intended application in the timber frame, but the specific derivation process of the grade is not necessary to know.

Do hardwoods always have higher F grade values than softwoods?

Hardwoods tend to have higher F grade values than softwoods, but this is not a strict rule as there can be variations among different species.

What is the purpose of the table showing the range of F values for different timber species?

The table provides an idea of the range of F values available for different timber species, helping to understand the relative strength of hardwoods and softwoods and to make informed choices in timber selection for construction.