How to calculate roof truss length

[Headless chicken]

so basically I am in the process of building a Wendy house for my daughter because I refuse to pay extortionate money for something that is crap. I've got the frame up just now need to sort out the roof.

So the question is how do I know how long to cut the wood to make the a frames to go on the roof?

Hope that makes sense!

 

[Bob c]

http://www.carpentry-tips-and-tricks.com/Rafter-lengths.html

 

[polk_farmer]

Make a dummy truss out of old or cheap wood. Have a tinker and then copy the rest from that when you've got it right.

 

[polk_farmer]

Get one of these, brilliant for cut roofing, accurate seat and plumb cuts once you have worked out the angle of the roof

 

[S J H]

Get one of these, brilliant for cut roofing, accurate seat and plumb cuts once you have worked out the angle of the roof

+1

Work out the angle you want, then set the square, cut the birds mouth, and leave them long, then mark the plumb angle on the rafter, sit both rafter on the plate then plumb them both up, and mark the cross point, then take off half the thickness of your ridge board, then use this as your template.

 

[Nearly]

Cardboard aided design.

 

[RWG Contracts]

I can't remember the way to do it easily but basically;

Let's say your wendyhouse is 5m wide with a 15 degree pitched roof so 2.5m to centre

So

(15 x tan) x 2.5 = 670mm

So we now know that your roof is 2.5 x 0.670 at centre so 2.5 squared + .670 squared, then square root = your rafter length

See piccy

 

[RWG Contracts]

 

[jf850]

A piece of string ??

 

[RWG Contracts]

A piece of string ??[/QUOTE

How longs a piece of string?

 

[Still Farming]

Bird mouth and sit on wall plate .
Go on "ready made trusses"firm ; Manderwood web site all info .

 

[Doing it for the kids]

How longs a piece of string?

Twice as long as half it's length

 

[RWG Contracts]

Twice as long as half it's length

Ahh yeah yeah of course. Makes sense

 

[Doing it for the kids]

Ahh yeah yeah of course. Makes sense

Used to say that to my uncle as a young boy to have the last say - wound him up terrible

 

[Philip Watkins]

I can't remember the way to do it easily but basically;

Let's say your wendyhouse is 5m wide with a 15 degree pitched roof so 2.5m to centre

So

(15 x tan) x 2.5 = 670mm

So we now know that your roof is 2.5 x 0.670 at centre so 2.5 squared + .670 squared, then square root = your rafter length

See piccy


View attachment 474126

Make it easy 2.5÷(cos15)=2.588. Don't need to do all that squaring and square rooting.

 

[RWG Contracts]

Make it easy 2.5÷(cos15)=2.588. Don't need to do all that squaring and square rooting.

I knew it was something to do with cos but couldn't remember what to do

 

[Philip Watkins]

I knew it was something to do with cos but couldn't remember what to do

It's so long since I did geometry it took me a while to remember it

 

[RWG Contracts]

It's so long since I did geometry it took me a while to remember it

Surprising how fast you forget

I've just realised why I couldn't get the answer, my calculator was set to "rad" not "deg"

 

[Philip Watkins]

Surprising how fast you forget

I've just realised why I couldn't get the answer, my calculator was set to "rad" not "deg"

I could remember SOHCAHTOA but not what to do with it

 

[ClusterClean Systems]

Hi M,

Use this website:

http://www.blocklayer.com/roof/gable.aspx

All the angle calculations and templates. Loads of other. Loads of calculations too.

We've been using it when we made a new garden office. Really quick and easy.