ESTIMATION OF ROOF COVERING

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INTRODUCTION

Roof is the one of the most structural parts in the building; roof is divided into roof construction system and roof covering in quantity surveying.

Roof construction system is the structural part of the roof that carries covering materials on it, it is the one which withstand loadings such as imposed loading from rainfall, wind, and snow.

Roof covering these are materials that are provided above roof construction to shed roof construction system, other parts of buildings, households and all furniture inside the building.



Knowledge of amount of roof covering materials required for building prior to construction is very important in preparation of construction budget.

In this post we look on how to estimate amount of roof covering material required for a simple building, the technique from this post can help to estimate roof covering of even complex roofs.

Types of roof materials

Roof of building can be covered by using different covering materials that are found at the markets such as tiles, shingles, slates and corrugated sheets.

Roof covering estimation

Roof covering estimation is the process that helps us to know amount of roof covering material that we can use to cover our building effectively with accordance to provided drawings.

On estimation of roof covering material there are two steps, that we need to be adhere so as to easy and effective estimation.

1. Calculation of roof covering surface area

This is the first step when the roof area is calculated, on which the covering materials will be laid; this area will comprise of overhangs and into gutter distances if specified.

2.  Estimating amount of roof material

This is the last step when roof covering material are estimated, this step involve estimation of effective coverage area of one roof material; covering materials are produced from industries with different sizes and construction specifications.

This difference bring difference in calculating effective coverage area of covering material, in this post we will use corrugated iron sheet as our roof covering material.


Basic concepts

Check on triangle below





STEP 2. ESTIMATION OF ROOF COVERING MATERIAL

In estimation of roof coverage materials we have two of covering material area we need to look into and different them.

a). Overall area of covering material.

This is the total area of the coverage material as it was produced from industry        without considering how it is going to be constructed.

For our corrugated sheet, overall area = 1.07 × 3.00

                                            = 3.21 m2

b). Effective area of covering material.

This is the area which considers how your roofing material will be laid on roof construction system; this area considers lapping lengths of covering materials.


Effective covering area of the roof covering material is calculated from its effective covering width and effective cover length, for our covering material with lapping length of 10cm.

Effective width = 107cm   10cm

                     =     97cm

Effective length  = 300cm 10cm

                     =      290cm

Effective area of cover material = 2.90m   0.97m

                                     =     2.81m2

Amount of roof covering material =

=

                                     =         23.2 corrugated sheets

Adding 10% up to 15% for any wastage that could occur during construction

                                     =         23.2 + 0.15(23.2)

                                     =     26.68

                                     =         27 corrugated sheets

Conclusion

Roof estimation is one most important knowledge that constructor must have.

In roof estimation, roof covering material has two areas that should not be interchanged; effective coverage area and overall coverage area.

Number of covering material can be calculated by dividing roof surface area by effective coverage area of material without forgetting addition of 10% to 15% for wastage.


OTHER RELATED POSTS

Types of roofs









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