huangyhg

dimensions on foundation plan
i work primarily with residential and smaller commercial projects, so this question may not apply to all. when i create a foundation plan drawing i have typically shown all the dimensions. many times i am just copying from a plan designer's drawing (or taking their cad file and manipulating) so that it has the appropriate structural notes and references. every so often a dimension gets mixed up (or revised without my knowledge) which leads to obvious field issues. i have heard of other folks just leaving dimensions off the foundation plan and basically refer to the architectural plans by others for all dimensions. is this a common practice?

imho, show all dimensions that are possible. if the plans are interpreted with a scale, the change of error goes way up. you are letting others, who do not have your insight into why specific dimensions have been selected, make the decision on what to use.
another reason is that certain copying processes change the size of the copied (paper) drawing. then a direct scaling of the copy will give the wrong answer.
also, if a field error is made that has to be corrected it will be very difficult for you to "prove" that your scaling of the drawings is "better" than someone else's.
putting an note on all drawings that says something like:
"drawings are not to be scaled" is often used on industrial projects.
slow a graphic scale on the drawing.
if you are the person responsible for the design, show dimensions once and show them correctly.
good luck
fss we do alot of similar work. some firms don't put any dimensions on the drawings (which is frustrating for the contractor & can lead to errors when the architect makes changes and no one is sure if the engineers drawings are updated or if they have the updated drawings. this can be a problem also if a beam span is increased or slab span).
the benefit of having no dimensions on structural is that the building will always fit on the foundation.
however in residential, it is generally up to the contractor/owner to review the drawings and flag any dimensional errors prior to constrution. it is also thier responsibilty to notify you of any changes. our firm puts a disclaimer on the drawings to this extent on all residential.
it is unreasonable to think you will be perfect and error free every set of drawings. the more responsibility the contractor assumes, whether it will hold up in court or not, the closer they will check things over as an extra set of eyes. if the contractor thinks something even "might" affect his pocket book, they will check things very closely. this is residential i am referring to mostly.
to date, any errors we have come across the contractors have been very willing to work with us to come up with a solution. hope that helps
based on the drawings provided by the architect, generate a layer of structurally relevant dimensions and show on your foundation plan. in the process of developing this, you may uncover many floating dimensions which need to be coordinated. keep a record of the date of the latest revision date of the arch drawing your work is based.
general notes should say that drawings shall not be scaled and when dimensional conflict exists, contact the architect for resolution prior to proceeding with work.
though many decent architects inform the engineer when they revise major dimensions affecting structural work, some fail to do this. this disconnect is the root of most dimensional issues from the field.
for multi story buildings, at levels above the foundation, i tend to leave out all dimensions already shown on the foundation plan and only indicate ones that are unique to that level.

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