Category: Design

Bushfire Upgrades

To determine exactly what is needed in the way of ‘Bushfire Upgrades’ .

A full examination of the location and the house design is required

Its your safety so its worth getting an expert!

Likely Extras

The following are typical extras for a Bushfire Attack Level (BAL) 12.5 zone:

  • All roof vents, wall vents and weep holes to have ember/spark guards made from corrosion resistant metal mesh with max aperture size of 2mm (See Photo)
  • External doors and windows to be provided with corrosion resistant metal mesh (steel aluminium or bronze)
  • Upgraded glass such as A-grade safety glass (min 4mm)
  • Weatherboards should be fibre cement (min 6mm thick). You may be able to use some external wood features but it will depend on the location and the type of wood
  • All external surface material joints less than 3mm
  • Weather strips or draught excluder to garage panel lift doors with a max gap of 3mm. (Roller door may be a better option)
  • A tiled roof to have full sarking  installed directly below roof battens
  • All external above ground gas and water pipes to be metal.
  • Protect air conditioning as it can ‘suck’ embers towards it. (See link for Evaporative Cooling)

Expect to pay an extra $5000 to $10,000 depending on the size of the house.

With a higher BAL , the cost will rise further with upgrades such as fire shutters.

Not Fire Proof

Its worth bearing in mind  that the upgrades will make your new home ‘Fire Resistant‘ not ‘Fire Proof

 

To find out more see: ‘What is the Bushfire Attack Level‘

 

Levels of Bushfire Attack

A Bushfire Assessment of your new house will put it in one of the following 6 levels:

Bushfire Attack Level

(BAL)

Description of Predicted Bushfire Attack and Levels of Exposure

BAL – Low

There is insufficient risk to warrant specific construction requirements

BAL – 12.5

Ember attack (Burning twigs, branches or leaves  airborne and carried  on the wind ) with heat flux* up to 12.5kW/ m2 (Heat flux = Amount of heat transferred per unit area per unit time to a surface)

BAL – 19

Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 12.5 and 19 kW /m2 

BAL – 29

Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 19 and 29 kW m2

BAL – 40

Increasing levels of ember attack and burning debris ignited by wind borne embers together with increasing heat flux (29 – 40 kW/m2) with the increased likelihood of exposure to flames

BAL -FZ

Direct exposure to flames from fire front in addition to heat flux and ember attack

*As a comparison the Heat flux from the Sun is around 400 W/m2.

 

Remember these levels are based on the BAL when the house is being planned. If you build and then fill the garden with shrubs and trees a few years later the Level, and the Risk, will be higher!

 

Don’t think that because you are in a suburb that you will be automatically be in a ‘BAL Low’ Area. Some suburban areas can still be at risk!

 

What Is The Bushfire Attack Level explains what factors are used in the Assessment

 

What is the Bushfire Attack Level (BAL)

The BAL is a number that indicates how severely a bush fire is likely to affect your new house. It comes from the Australian Standard AS3959 – 2009.

The number is calculated by considering the following  factors:

  1. The Fire Danger Index (FDI)   The probability of a bushfire starting, speed of spread, intensity and difficulty of fighting the fire.For Victoria the FDI is 50 for an alpine area or 100 elsewhere. For other states you will need to check with your state regulations.
  2. Classification of Nearest Vegetation   In all directions. 
    • A – Forest
    • B – Woodland
    • C – Shrubland
    • D – Scrub
    • E – Mallee / Mulga
    • F – Rain Forest
    • G – Grassland
  3. Distance to Vegetation   Horizontal distance to the main part of the house.
  4. Slope   This is the slope of the vegetation, not the slope of the area between the vegetation and the house.

In the above example this is a ‘Down Slope’ as the slope of the vegetated area is Down as it goes away from the house ((Even though the intervening space slopes up). ‘Down Slopes’ are higher risk than ‘Up Slopes’ because fire moves quicker going up hill.

By the use of tables the FDI can be calculated for each direction with the highest value being the overall FDI.

Although it is possible to get guides and do it yourself (For example: Victorian Building Authority) I think where safety is involved it’s worth getting an expert in. They will be able to do the assessment and give you advice on requirements and improvements.

 

This link explains the various BAL ‘Scores’

Roof Trusses

Although  roof trusses only started being used in Australia in the 1960’s they now have around 80% of the total ‘Pitched Roof’ market.

They are all designed using well proven computer programs and manufactured in factory conditions. (the whole process is high tech and relies on specialised equipment…….site work is limited to erection of the completed trusses).

Trusses can span large areas without needing intermediate supports. Because the individual components are engineered to share the stresses acting on the roof the total amount of timber is usually much less than an equivalent ‘Conventional Roof’.

Components

The following diagram is of a standard timber roof truss.

For more complex roof shapes there are a range of special trusses that can be made.

Steel roof trusses would look generally similar although they would use a different jointing method rather than nail plates.

The timber components are normally pine and will be either ‘F’ or ‘MGP’ graded. The size is determined from the  manufacturers computer program.

Nail Plate (or Gang Nail)

The chords and webs are joined by nail plates. The plates are galvanised steel sheets that have spikes protruding on one side.

 

The plates are hydraulically pressed into the timber at the manufacturing plant, with one plate on each side of the join. They form a solid fixing that is very strong.

As well as joining chords and webs they are quite often used to splice timbers together particularly when a long bottom chord is needed.

 

 For more about house construction see: Basic Timber Frame

 

 

World’s Biggest Houses

New Australian homes are now the worlds biggest.

Here is a diagrammatic representation of the size compared with three other countries.

and here are the average home sizes  in square metres:

Australia

214
USA

201
Greece

126
Germany

109
Spain

97
Italy

81
Britain

76
China (Urban Only)

60
Hong Kong

45

Source http://reneweconomy.com.au

In the last 25 years while the size has increased by 10% while the average number of people per household has dropped from 2.7 to 2.6.

Instead of complaining about ‘Housing Affordability’ why aren’t we just building smaller houses?

 

See this post to see the size you need: How Much House?

 

 

Steel Wall Frames

With a steel frame house a standard wall panel, other than using a different material, is much the same as a Basic Timber Wall Panel.

Once it comes to a panel with openings there are a few differences as the sketch below shows:

Typical differences are:

Diagonal Brace

The diagonal braces are used (instead of a panel of sheet material in the timber frame) to resist sideways forces on the frame.

Lintel

Rather than a solid beam a truss structure is formed to carry loads over the opening.

 

 

Also check the following links:

Brick Veneer

House Construction – The Frame

Timber or Steel Frame

 

Upstairs Windows

 

Have you got visions of being able to look out of your upstairs bedroom windows like this lady.

Not anymore if you are building a new house. New laws to protect children falling out of windows have come into force.

Since 1 May 2013, the Building Code of Australia (BCA) requires “protection for openable windows in new homes where the floor below the window is more than 2m above the surface beneath” (i.e. 2-storey homes).

The protection is either a device to restrict the window opening, or a  screen, so a 125mm diameter sphere (representing the size of a young child’s head) cannot pass through. The device or screen must also be able to withstand an outward  horizontal force of 250 N.

 

The picture is called “By the open window” painted by Konstantin Makovsky.

 

For more about windows see : Glazing

Timeless Design

How old do you think this house is?

What do you think 2 years, 5 years, or even 10 years old.

It looks fairly modern with the ground floor brick and the upper floor a contrasting material. those wide eves look impressive and give good solar shade

Well this is known as the Susan Lawrence Dana House, in Springfield, Illinois.

It was designed by Frank Lloyd Wright who was famous for the ‘Praire House’ style.

Thanks toFrank Lloyd Wright Tours for the photo. (Going on one of their tours is on my Bucket List!)

And the house? . . . . . It was completed in 1904, so it’s more than 100 years old.

Do you know any other timeless designs?

 

Children’s Bedrooms

Some people want children’s bedrooms to be big!

I’m not so sure!

Reasons for Big Bedrooms

  • Room to play, study, have sleepovers and for all their stuff.
  • Room for adult children.
  • Better for resale value.

(Big for me is 9 square m or more.)

Reasons for Small Bedrooms

  • Discourage  children from staying in their rooms.
  • Encourage children to move out when they become adult.
  • Keep initial cost down.

(Less than 7 square m I would consider to be small)

Overall

Well both my children have left home and we have now living in an apartment which is too small for them to move back!

If I was building a house for children I would probably go more for the smaller bedrooms.

I think being able to supervise children and encourage them to be more social is worthwhile. Most houses now have rumpus rooms so that’s where the toys can be stored and sleepovers take place.

What do you think?

 

Whatever size of bedroom make sure that you have thought about the power points, one thing which is often neglected by builders. See this link: Electrical Planning – Secondary Bedrooms

 

Openings in Timber Frame

Openings in a Timber Frame Wall Panel usually mean that the Bracing Straps of the Basic Frame can’t be installed.

The following diagram shows typical panel details.

Bracing Panels

The bracing panels replace the bracing straps to keep the frame square and ensure the panel resists sideways forces. They are a sheet  material that is nailed to the studs top plate, bottom plate, and noggins.

Usually the panels are ply although I have seen other materials such as particle board.

Lintel

The lintel carries loads from above to the studs either side of the opening. The size of the lintel will depend on the width of the opening

Jam Stud

The jam stud in normally the last full height stud before the opening

Secondary Jam Stud

As well as assisting the jam stud to carry the lintel load the Secondary Jam Stud also provides extra stiffness to counteract the fact that there is only one noggin.

Sill Trimmer

This forms a fixing point for a window frame, and also the top fixing point for any Jack Studs.

NB for a small window a Head Trimmer may be used between the lintel and the top of the opening

Jack Stud

The jack stud is a short vertical stud. It can be between:

  • The Bottom Plate and the Sill Trimmer
  • The Lintel and a Head Trimmer

For background information about House Frames see this link: House Construction – The Frame.

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