# Forum Home Renovation Structural Renovation  what size wood is used in framing of houses?

## wozzzzza

*what size wood is used in framing of houses?* .  
would 90x35 be suitable??

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## seriph1

You really need to check with a qualified builder/chippie or at least your local building supplies people because size isnt really the issue - rather, the material's "rating" is what must be used to determine suitability for an application.

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## Bloss

Depends on the design - generally external framing is 90x45 sometimes 90x35 - and the overall structure has to be designed around that choice. You could use 70x35 and design around that too, but that is more commonly used on internal walls to save space and or money. As seriph1 says the timber has to be to a certified quality that complies with AS1684 (timber framing standard) and the BCA. :2thumbsup:  
Then again that might be a trick question - the answer could be 'no timber' if steel framed!  :Biggrin:

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## GraemeCook

In my old home town, Boston, USA the standard for wall studs was changed some 30 years ago from 4x2 inches to the current standard of 6x1.5 inches.   The reason for the change was that the larger internal wall cavity allowed for more insulation. 
Cheers 
Graeme

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## Smithers

The minimum size for radiata pine MGP 10 is 90 x 35 for external wall frames and 70 x 35 for internal.

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## Stan 101

70x35 pine can be an is still used extensively in Qld. The thing that governs the size / grade / stud centres / plates is the load being applied and therefore the tie down requirement.  
Three loads are used to in construction: Dead, Live and Wind. 
Dead load (or gravity) refers to the total mass of the building you need to hold up. This includes tiles, roof sheeting and the like. It also includes the self weight of the building materials. 
Live load is a temporary load such as walking on the roof, having stacks of tiles sitting in a small area etc. 
Wind or uplift load is basically a suction where the roof structure acts as a kite and it trying to be lifted.  
The first thing to decide on is the RLW or roof load width. What is the maximam span of roof in the building? The second is the tie down centres for the job? Third you must look at critical load mass. EG: The whole job can deal with a 70mm frame tied down at 1200mm centres except for the requirement of a girder truss that is of a span of 9000mm and is carrying a roof of 9000mm. The bearing of the girder then becomes the most critical part of the job. 
5 studs of 70x35 f17 hardwood may not withstand the bending forces of the weight bearing on it so the easiest solution may be to use a 75mm shs steel post to support it or jump the frame up to 90mm. 
The other critical issue here is plate crush under the girder's bearing point. Pine or hardwood might not suffice in this instance and a 6mm steel plate for instance may be requyired to spread the load. 
Going to 90mm might allow you to revert back to 1800mm centre tie down as opposed to 1200mm tiedown. 
But as a rule, 70mm framing is often more than adequate for standard span domestic housing..  
cheers,

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## pykie

> *what size wood is used in framing of houses?* .  
> would 90x35 be suitable??

  
As a rule of thumb: 
90 x 35 (MGP10) @ 450 centres for the external walls, on critical load points, have 90 X 45 kd hardwood studs, all your double studs for window and door openings should be 90 X 45, your wall plates should be 90 X 45 
If it is a trussed roof, then 90 X 35 @ 600 centers will suffice (personally I do it at 450, its a small price to pay for the quality of fixing on the plaster etc). If you have any girder trusses sitting on internal walls, make sure there are studs of sufficient grading to take the load.

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## Stan 101

Hi Pykie. I don'r mean to be rude as I am also new here. But that last post is simply incorrect. For small span dwellings it may suffice as 90x35 studs but p10 will not always be adequate. Also, loadings under critical trusses must be assessed individually. 
As mentioned in my previous post, plate crush on both the top and bottom plates must be taken into account as well as sheer.  
cheers,

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## Pulse

> The minimum size for radiata pine MGP 10 is 90 x 35 for external wall frames and 70 x 35 for internal.

  Sorry, no such rule in AS 1684.2 
The answer to this thread lies in the timber framing manual AS1684, no other answer really, everything else is just local/personal habit, AS 1684 is the definitive answer. 
To answer the post, 90x35 is probably good enough if AS 1684 says so (ie RLW, wall height, top and bottom plate sizes, point loads, jamb studs for openings etc..  
Pulse

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## CelticCarpentry

as the original poster has not given much detail in regards to the house being built, e.g. one or two storey. i will assume the OP does not have planning permission, architectural or engineering plans.
therefor i recommend mgp12 90x35. if you need timber treated for termites, ask for t3.  
regards, justin.

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## wozzzzza

> as the original poster has not given much detail in regards to the house being built, e.g. one or two storey. i will assume the OP does not have planning permission, architectural or engineering plans.
> therefor i recommend mgp12 90x35. if you need timber treated for termites, ask for t3.  
> regards, justin.

  in very early stages of design at the moment. wanna find out stuff before i go submitting plans etc..
will be building an outdoor room about 3.5m wide and 7 metres long.
if there any more info, keep it flowing. wanna build it like a house with trussed iron roof and iron walls with plasterboard on inside.

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## bilrob

Where in AS1684 or the NSW framing manual does it specify different size studs for 
external and internal walls? 
I have used 75x50 f11 throughout upper and lower storeys  both external and internal. 
Now I  am starting to panic.

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## Cooky

Keeping in line with my trade of engineering... 
I say all internal and external studs must be 290 x 45 KD Hardwood. No exceptions.  
Just in case a bus falls on your house  :Biggrin:

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## Cooky

BTW bilrob, my guess is that your fine with 70x50 F11 studs. A bit unusual, but F11 is pretty decent timber, it's got a stress grade almost double that of MGP10. So you can settle your little panic attack down  :Wink 1:

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## pykie

> Hi Pykie. I don'r mean to be rude as I am also new here. But that last post is simply incorrect. For small span dwellings it may suffice as 90x35 studs but p10 will not always be adequate. Also, loadings under critical trusses must be assessed individually. 
> As mentioned in my previous post, plate crush on both the top and bottom plates must be taken into account as well as sheer.  
> cheers,

  
As I said, it is a rule of thumb, Ive obviously got no specifics to work with.  
And I wasnt referring to small dwellings, I recently framed a 55 sq/m house using with that method. 
Most new dwellings in Victoria take 90 x 35 studs, excpet in load bearing points. volume builders revert to 70 X 35 for internals etc.

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## China

Check with your council you may be supprised at what will happen to your rates, my mate did this it stirling and his rates doubeld, aparently it is all to do with the size and what it is classed as

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## bilrob

Am I missing something here? 
What on earth has the size of the timber frame to do with how much council rates you pay? 
Now I am really scared!

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