That moment you realize your reference layer is 20 years old

I was drafting a remodel for a house built in 2003 and pulled the old prints from the city. Turns out the original drafter used a different datum for the elevations. I cross checked with a laser measure and found a 4 inch difference between the plans and the actual foundation height. How do you guys catch stuff like this before it becomes a problem on site?

3 comments

3 Comments

terrybennett1mo ago

Man, learned that one the hard way too - always double check benchmarks with your own gear before cutting anything.

carr.brooke1mo ago

There's always something hiding in the old plans that nobody thinks to check. I've seen guys trust a twenty year old benchmark without ever pulling out a level on site. What catches most people off guard is that the original crew might have worked off a temporary benchmark that got lost or moved over time. A four inch difference is huge if you're tying into existing windows or doors. Best habit I ever learned was to shoot your own elevations the day you start, no matter how old the prints are.

xenagarcia1mo ago

Whoa hold up. I mean yeah a 4 inch difference sounds bad but is it really that big of a deal? I've worked on houses from the 80s where the foundation settled a good 2 or 3 inches and everything still lined up fine because the framing just flexed a little. Plus if the existing windows and doors were framed to the old datum anyway then your new work just has to match what's already there not some mythical perfect number on a piece of paper. I guess I'm just not sure why everyone acts like a few inches is the end of the world when lumber isn't even perfectly straight to begin with. Seems like a lot of hand wringing over something a couple shims can fix.