1 construction blueprint reading grid lines and key plans

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CONSTRUCTION BLUEPRINT READING

GRID LINES AND KEY PLANS

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Grid lines are a very important component on blueprints, especially for large construction projects.

They will appear on the structural, architectural and electrical drawings.

These grid lines are similar to the grid lines used on road maps and serve the same purpose, to locate a specific area on the project.

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On one side of the drawing a series of numbers will be present with connecting lines attached to the perimeter of an object and passing through to the other end.

On the top or bottom of the drawing a series of letters will be present.

The combination of a letter and a number is used to pin point a specific location on the drawing.

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Foundation plan showing grid lines:

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When looking at the I-beams on a drawing you will notice that there are all typically spaced the same distance apart.

Normal spacing between I-beams is 20’ to 25’, knowing that can enable you to do quick length calculations for cable footages and device placements.

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The I-beams along the top are spaced 18’ apart.

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Grid lines typically line up with the I-beams on a project, each I-beam will have either a letter or number designation and they are spray painted onto the I-beams.

This method of using lines allows contractors to indicate half way points between grid numbers and letters, i.e.

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In many cases certain letters and numbers are omitted from the grid line system to avoid confusion.

0, 1, I, O, and Q are usually omitted form the grid line system.

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Using the grid lines, where is the center of the TR located?

APPROX. M.3 X 2.8

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CONSTRUCTION BLUEPRINT READINGWHAT IS LOCATED AT L.5 X 2.5? FLOOR MOUNT ELEC./ V&D OUTLET

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By using the prints and looking at the numbers and/or letters on the steel columns you can orient yourself on site.

Grid lines along with the north symbol will frequently be used to identify spaces and parts of the building.

In the previous slide the electrical room and telecom room are located on the east side of the building.

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On large construction projects it’s necessary to cut a building up in sections so that they will fit on a drawing sheet.

To do this architect's use a key plan that will appear in the drawing area of every plan, the purpose of the key plan is to identify that part of the project to which the sheet applies.

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The un-shaded portion of the key plan appears on other drawings, the shaded section of a key plan is the portion of the project represented on the drawing sheet that you’re looking at, in some case the shaded portion may be represented by cross hatched marks instead of shading.

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This project has four different sections; A, B, C and D, this means that there is a full set of blueprints for each section all included in the original roll of blueprints.

There will be a match line that separates each section and there is a little overlap from one section to the other.

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The key plan indicates that you’re looking at section D

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As you move from section to section pay close attention to the match line.

If you’re counting locations for a material count remember that there is overlap between sections so you could easily double count items.

That means you will have to compare two sets of drawings for accuracy.

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CONSTRUCTION BLUEPRINT READINGWHERE IS THE MATCH LINE LOCATED?

H.4

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WHY IS THE GRID LINE SYSTEM MISSING THE “1” AND THE “I”?

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During the course of a project many changes will be made both small and large, when this occurs an addendum will be generated.

An addendum is an official document that describes the changes to take place, this might mean moving a wall 1 foot or turning an office into a storage room.

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Addendums will include a NTS drawing showing the changes to take place and a scope of work to be done.

The addendum will indicate the area to change using the grid line system and will be signed off by the architect or general contractor.

The addendum becomes an official legally binding document and should be treated as such.

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Conversely, if you notice a discrepancy with a section of the building your working in, or if just need clarification with a section of the drawings you can generate an RFI (request for information).

You will need to indicate what part of the building your requesting info for and the best way to do that is using both the key plan and grid line location.

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Based on the information provide which section is the work on this projected been done in?Is it the North, South, East or West wing?

SECTION “D”

WEST WING