Outcome-Based Course Module.

Iloilo Science and Technology University Architectural

Drafting Technology: COST ANALYSIS AND ESTIMATE

MODULE: COST ANALYSIS AND ESTIMATE

Module Introduction/Rationale:

In this module you are about to determine the required materials for a roof
framing and its possible cost.

Later on you will be required to have a computation based from your own
house plan.

Module Outcomes:

Upon completion of this module, you should be able to:

1. identify various cost of building materials
2. estimate own basic building materials
3. practice accuracy in solving a problem regarding building
materials
4. decide how to simplify complicated problems

Lesson Title: Roof Framing Estimation

Lesson Outcomes:

At the end of this module you are expected to have:

1. determined roofing materials
2. estimated the cost of roofing materials

Key Concepts/Words (Optional)

Truss C-purlins
Half Truss
Valley

Activate:

Estimating the roof framing is very crucial to your budget.

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 Outcome-Based Course Module. Iloilo Science and Technology University Architectural
Drafting Technology: COST ANALYSIS AND ESTIMATE

In reality the roof framing detail would be carefully studied prior to the
computation, so later on better carefully check your plan before going into it.

Acquire:

1. What is a roof framing plan?

A roof framing plan is a layout of a roof that contains mainly the truss,
halftruss and purlins.

EXAMPLE:

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 Outcome-Based Course Module. Iloilo Science and Technology University Architectural
Drafting Technology: COST ANALYSIS AND ESTIMATE

T = Truss
HT = Hip Truss
CB =Center Beam
VG =Valley Gutter

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 Outcome-Based Course Module. Iloilo Science and Technology University Architectural
Drafting Technology: COST ANALYSIS AND ESTIMATE

ILLUSTRATION:

Item 1. Estimation for Roof Framing Materials.

1. Refer to Roof Framing Plan.

Take note of the labels for the Roof Framing members.

T (main truss) : 4 sets

HT (hip truss) : 4 sets
VG (valley gutter) : 2 sets

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 Outcome-Based Course Module. Iloilo Science and Technology University Architectural
Drafting Technology: COST ANALYSIS AND ESTIMATE

CB (center brace) : 1 at 7.00 lgth

:1 at 2.00 lgth.

2. Check the details of the Roof Framing members.

As Noted, the detail of CB is the same for HT and VG.

VG has a length of 3.50 m while HT has 1.72 m in length

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 Outcome-Based Course Module. Iloilo Science and Technology University Architectural
Drafting Technology: COST ANALYSIS AND ESTIMATE

3. Compute for the T (main truss).

By direct scaled measurement, the length of the truss' rafter is 10.70 m.

Compute top chord:

= 5.13 x 2 angle bars per rafter

= 10.26 m x 2 rafters
= 20.52 m x 2 top chords
= 41.04 x 4 sets of T (main truss)
= 164.16 m / 6.00 lgth of angle bar
= 27.36, say 28 lgth of 1/8 x 1 1/2 angle bar

Compute for the bottom chord:

= 2.55 x 2 angle bars per rafter

= 5.10 m x 2 rafters
= 10.20 m x 2 top chords
= 85.60 x 4 sets of T (main truss)
= 20.40 m / 6.00 lgth of angle bar
= 3.40, say 4 lgth of 1/8 x 1 1/2 angle bar

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 Outcome-Based Course Module. Iloilo Science and Technology University Architectural
Drafting Technology: COST ANALYSIS AND ESTIMATE

4. Compute for the HT (hip truss).

The HT will make the form of the hip-like end of the roof.

We cannot see in the details what is the approximate length of HT, but we
can assume safely to add 50% of its indicated span in the plan as a rule of
thumb.
= 1.00 m + 50%
= 1.50 m x 2 angle bar per rafter
= 3.00 m x 2 rafters
= 6.00 x 4 sets
= 24.00 m / 6.00
= 4 lgth of 1/8 x 1 1 /2 angle bar

5. Compute for the VG (valley gutter) frame.

Like HT, we cannot see in the details what is the approximate length of
VG, but we can assume safely to add 50% of its indicated span in the plan
as a rule of thumb.
= 2.00 + 50%
= 3.00 m x 2 angle bar per rafter
= 6.00 m x 2 rafters
= 12.00 x 2 sets
= 24.00 m / 6.00
= 4 lgth of 1/8 x 1 1 /2 angle bars

6. Compute for the CB (center brace). Total length of the CB is 9.00 m.

= 9.00 x 2 angle bar per rafter
= 18.00 m x 2 rafters
= 36.00 m / 6.00
= 6 lgth of 1/8 1 1/2 angle bar

7. Compute for the 10mm RSB lacing.

As indicated in the details, in every 0.50m span we have a 0.30m vertical
and 0.65 m diagonal lacing.

Compute the total length of the truss members.

T (main truss) : 4 sets x (5.13 + 2.55)

= 30.72 m

HT (half truss) : 4 sets x (1.00 + 50%)

= 6.00 m

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 Outcome-Based Course Module. Iloilo Science and Technology University Architectural
Drafting Technology: COST ANALYSIS AND ESTIMATE

VG (valley gutter): 2 sets x (2.00 + 50%)

= 6.00 m

CB (center brace): 1 at 7.00 lgth

: 1 at 2.00 lgth.
= 9.00 m

Total: 51.72, say 52.00 m

Compute:

= 52.00 / 0.50
= 104 spans
= 104 x (0.30 + 0.65)
= 98.80 m / 6.00
= 16.47, say 17 lgth of 10mm RSB

8. Compute for the purlins.

Refer back to the Roof Framing Plan.

The VG and HT are at 45o horizontal inclination, so whatever excess of the

length of a purlin in one side will be put on the other perpendicular side

By direct counting on the right side of the plan:

= 10 pcs x 9.00 m lgth

= 90.00 m x 2 sides
= 180.00 m / 6.00
= 30 lgth of 2x3 c-purlins at 0.60 m o.c.

9. To solve for the entire span of the gutter we need to refer to the elevations
and use measure by scale. Assume that we already did and we have
solved the entire span of the gutter.

= 40.00 m

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 Outcome-Based Course Module. Iloilo Science and Technology University Architectural
Drafting Technology: COST ANALYSIS AND ESTIMATE

Refer to Fascia Frame Detail. The material to be used are 2x6 and 2x3
cpurlins as frames.

Compute the quantity:

= 40.00 m / 6.00
= 6.67, say 7 lgth

= 7 lgth of 2x6 c-purlins = 7

lgth of 2x3 c-purlins

10. Compute for the consumables.

The total horizontal area of the roof framing is:

= 7.00 x 9.00
= 63.00 sqm

From the Rule of Thumb:

welding rod

= 63.00 x .35 kg per sqm

= 22.05 kg

4" grinding disk

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Outcome-Based Course Module. Iloilo Science and Technology University Architectural
Drafting Technology: COST ANALYSIS AND ESTIMATE

= 63.00 x .15 pcs per sqm

= 9.45, say 10 pcs

4" sanding disk

= 63.00 x .10 pcs per sqm

= 6.3, say 6 pcs

Summary:

• 1/8 1 1/2 angle bar

= 28+4+4+4+6
= 46 (lgth) x Latest cost

• 10 mm RSB
= 17 (lgth) x Latest Cost

• 2x3 c-purlins
= 30+7
= 37 (lgth) x Latest Cost

• 2x6 c-purlins
= 7 (lgth) x Latest Cost

• welding rod
= 22 kg x Latest Cost

• 4" grinding disk

= 10 pcs x Latest Cost

• 4"sanding disk
= 6 pcs x Latest Cost

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 Outcome-Based Course Module. Iloilo Science and Technology University
Architectural Drafting Technology: COST ANALYSIS AND ESTIMATE

References:

▪ Fajardo, Max, Simplified Construction and Estimates, 5138

Merchandizing, 2000 Edition
▪ Tagayon, Vicente A., Estimating Bill of Materials, Tagayon
Associates, 2002
▪ Velasco, Rheno A. Handbook of Construction Estimate, Loacan
Publishing & Rheno A. Velasco, 1997
▪ Haro , Dynn G. Unpublished Thesis: CD-Based Reference Guide for
Residential Construction, 2006.

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Outcome-Based Course Module. Iloilo Science and Technology University
Architectural Drafting Technology: COST ANALYSIS AND ESTIMATE

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