General Plans and Details Flashcards
Dimensions - Accuracy
Dimensions are accurate to 1/2 the smallest unit indicated. NOTE: THIS COULD TRICK YOU IF YOU DON’T PAY ATTENTION! If a dimension is expressed as 1’-0” you MUST LOOK AT THE 0” part and understand that they are showing inches as the smallest unit. So 1/2” would be correct answer here. If it instead was showing a 1’ dimension, then the inches part is being left out and the smallest unit is a foot, so 6” (1/2 a foot) would be the correct answer. PAY ATTENTION!!! Also note that while the dimension 84’-3” and 84.25’ are both the same measurement, the first represents an accuracy of 1/2” while the second is based on 1/2 of a one hundreth (0.01) of a foot or 0.005’ which is about 1/16th of an inch. So how a dimension is shown matters.
Dimension - Field
Dimensions that must be measured on site, usually after site elements have been constructed. E.g. a custom gate for a stone wall. The opening would be measured once it is constructed and the gate made to fit that ‘field dimension’
Dimension - Fixed
Dimension that locates site elements with a high level of accuracy and usually for legal purposes. Things like ROW lines, property lines, building locations, setbacks, and other code requirements.
Dimension - Flexible
Flexible dimensions locate site elements that do not require exactness in terms of their form and positioning and suggest greater tolerance with regard to acceptable levels of accuracy. The dimensions may be adjusted based on field conditions as long as there are no legal ramifications as a result of these modifications and the overall intent of the design is not compromised. Because of their flexibility, these dimensions are often referred to as floating dimensions and are indicated by ± signs. Features included in this category include free-form geometries like curvilinear walks and paths and planting bed lines, as well as utility lines and structures. It should be noted that plantings and movable furnishings such as tables and chairs, planters, and trash receptacles are generally not dimensioned.
Dimension - Semifixed
These are located in reference to fixed dimensions. Points, lines, and planes located by fixed dimensions serve as the bases to which semifixed dimensions are referenced. Site features that would be located with semifixed include sidewalks, terraces, parking areas, walls, fences, and other landscape elements. Semifixed dimensions can also be used to locate other semifixed and floating dimensions. In most circumstances, the majority of site dimensions are semifixed dimensions.
Grading (Conditions that are difficult to work with)
Soils that pose particular difficulties and should be avoided or removed when grading are loose silts, soft clays, fine water-bearing sands, and soils with high organic content such as peat (except in planting beds). Other critical conditions in grading soils are a high water table or rock close to the surface.
Grading, Constraints of (legal)
Property lines establish a legal boundary between property owner and adjacent use. The existing grades at the property line can not be altered and thus become a controlling factor. This also affects the flow of stormwater runoff from one property to another. It can not be increased beyond what was there before the owner purchased it.
Grading, Slopes
To be visually significant, slopes should not be less than 5:1 (H:V). Generally, planted slopes should not exceed 2:1, but paved slopes may be 1:1 or greater. Mowed lawn areas should not exceed 3:1, although 4:1 is the preferred maximum. The use of slopes and the selection of a desired gradient are based on the design intent, soil conditions, susceptibility to erosion, and type of surface cover. All slopes must be stabilized by vegetative or mechanical means to reduce erosion potential.
Grading, Terraces
Terraces provide a series of relatively flat intermediate levels to accommodate a change in grade. The reasons for terracing may be visual, functional, or structural and may be created by the use of slopes or walls or a combination of both. Where both the slope and the level portion, known as a bench, are relatively small in area and grade change, it is possible to pitch the bench in the downhill direction. However, where grade changes and area of slope are considerable, as in a highway cut or fill, the bench must be pitched back from the slope to reduce erosion. The storm runoff from the bench must be properly disposed of to prevent saturation of the toe of the uphill slope, which could cause the slope to slump.
Grading, Finished Landscape Grades
As a general rule, landscape finished grade should be 6 inches below the finished floor elevation of a structure. Note that in exterior conditions, it is often ideal for the landscape finished grade to be around 2 inches below the finished surface elevation of adjacent hardscape surfaces such as sidewalks and pool decks. This is to prevent mulch running out of the planters and other such conditions.
Hachures
Lines on a contour map showing a depression. They are just little lines (like a hatch or teeth) that extend inward toward the depression.
Layout Plan
A dimensioned plan showing the location of objects in a site based on set points that can be located by a surveyor.
Layout Plan (Fixed Dimensions)
Dimensions that are used for legal purposes like property lines, ROW liens, building locations, building setback, and other dimensions governed by code requirements.
Layout Plan (Semifixed Dimensions)
These are dimensions that are based off of fixed dimensions and are used to locate site objects like sidewalks, walls, fences, parking areas, etc. It does not mean, however, any degree of lower accuracy than a fixed dimension.
Layout Plan (Flexible Dimensions)
Dimensions that locate site elements that do not require exactness in terms of their form and positioning. Path of an underground utility line can be shown as +/- due to possible onsite element conflicts. So that dimension might grow or shrink based on the path of travel. Also can be called “floating dimensions”.
