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A home is gotten when you look for comfort based on your fantasy, but a shelter is a necessity, and a building becomes a shelter when it can prevent rain,water,sun, strong wind and other climatic elements from affecting the occupants- human,animal, living and dead loads with personal effects.

As far as I am concerned the moment you have your roof placed on a building, other things are important but they are basically needs. You can’t move into a house without a roof , but we have seen people living in a house with no window or makeshifts windows covered with ordinary bags and cardboards.

So it is very important to calculate the dimension of the true length of a roof members. These dimensions are essential to determine the accurate span of Rafter, Wall plate, Tie beam, King Post, Overhang, Purlins, fan struts etc.

Residential timber-framing construction clearly differentiate between spacing and span Spacing the centre-to-centre distance between structural members, unless otherwise indicated.

Span the face-to-face distance between points capable of giving full support to structural members or assemblies. In particular, rafter spans are measured as the distance between points of support along the length of the rafter and not as the horizontal projection of this distance.

Single span the span of a member supported at or near both ends with no intermediate supports.

Continuous span the term applied to members supported at or near both ends and at one or more intermediate points such that no span is greater than twice another.

Span/length calculation for roof members.

As can be seen the span of the rafter in the figure below is not quite in agreement with the Code but we will use the figures for the rafter span as calculated below.

Wood/ timber are sawn into various sizes amongst are

2” by 2” i.e 50mm by 50mm

2” by 3” i.e 50mm by 75mm

2” by 4” i.e 50mm by 100mm

2” by 6” i.e 50mm by 150mm

3” by 4” i.e 75mm by 100mm

3” by 6” i.e 75mm by 150mm

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With the diagram above applying Pythagoras theorem

X2 (rafter length )=4.52+3.52

X=5.7m

Rafters are nailed side by side tie beam and struts. So we use the numbers of pieces of tie beams because they are also spaced at 1.2m center to center and multiply by 5.7m

15 pcs of rafter (same as tie beam) multiply by 5.7 =85.5m

Now divide by 3.6m to know the numbers of 3” by 4” to purchase in market=24 pcs of 3” by 4” required for rafters.

PURLINS are the wood of 2” by 2” or 50mm by 50mm we nail the roofing sheets on.

Purlins are spaced based on designs or type of roofing sheets. But for our calculations, we are using 900mm spacings.

Going by diagram above add 5.7m +5.7m for both sides=11.4m

Divide 11.4m by 0.9m to know the numbers required =13 pcs of purlins of length 18.175m (The purlins has to span the length of the building which is 16.975 plus 1.2m for the overhangs by sides)

So 13 by 18.175m=236m

Now divide by 3.6m to know the numbers requires to purchase in market =236/3.6

=66 pieces of 2” by 2” to purchase in market for the purlins.

KINGPOST is that piece of wood that stands at the middle of two rafters falling at the opposing sides. Is the one that spans vertically from the tie beam/rafter line, so just the same way we calculated for rafter, remember 15 pieces and multiply by the height of the roof 3.5m=52.5m

Then divide by 3.6m to know the numbers to buy in the market.

Therefore 15 pieces of wood of 2″ by 6″ termed kingpost is needed to be bought in the market.

Credits of this Articles goes to:
http://buildingcontractorsecrets.com/2012/12/how-to-calculate-timber-roof-members/

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A home is gotten when you look for comfort based on your fantasy, but a shelter is a necessity, and a building becomes a shelter when it can prevent rain,water,sun, strong wind and other climatic elements from affecting the occupants- human,animal, living and dead loads with personal effects.

As far as I am concerned the moment you have your roof placed on a building, other things are important but they are basically needs. You can’t move into a house without a roof , but we have seen people living in a house with no window or makeshifts windows covered with ordinary bags and cardboards.

So it is very important to calculate the dimension of the true length of a roof members. These dimensions are essential to determine the accurate span of Rafter, Wall plate, Tie beam, King Post, Overhang, Purlins, fan struts etc.

Residential timber-framing construction clearly differentiate between spacing and span Spacing the centre-to-centre distance between structural members, unless otherwise indicated.

Span the face-to-face distance between points capable of giving full support to structural members or assemblies. In particular, rafter spans are measured as the distance between points of support along the length of the rafter and not as the horizontal projection of this distance.

Single span the span of a member supported at or near both ends with no intermediate supports.

Continuous span the term applied to members supported at or near both ends and at one or more intermediate points such that no span is greater than twice another.

Span/length calculation for roof members.

As can be seen the span of the rafter in the figure below is not quite in agreement with the Code but we will use the figures for the rafter span as calculated below.

Wood/ timber are sawn into various sizes amongst are

2” by 2” i.e 50mm by 50mm

2” by 3” i.e 50mm by 75mm

2” by 4” i.e 50mm by 100mm

2” by 6” i.e 50mm by 150mm

3” by 4” i.e 75mm by 100mm

3” by 6” i.e 75mm by 150mm

HsLBroker:
4 your construction call or WhatsApp 08182481552

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Thanks for your interest, i used akun for the 3x4x12 (wall plate) @ N800, same for the 2x4x12 @ N500 for the (king post and Tie beam) Also used Akun for the 2x3x12 for the ( the purlin) @ N400, I used Ire and Ogborugboru for the Ceiling Nogging 2x2x12 @ N300 but i don't used Akun for the 2x2x12 because some of them will break when using 3inches nails on it and may cause problem for the ceiling sheets when attaching it. Akun for the 1x 10 x 12 @ N1700 plus smoothing (the facial board)

Riscoded:

What's current price for wood now?