Ive handled a ridiculous amount of renovation work, both Residential and Commercial. And you have my number, hehe.

As far as that goes, i dont model Existing to any lesser detail than i model new work. Why would i? A stud wall is a stud wall. I use the same wall types in New that i did in Existing, except i set the existing ones to, well, existing.

I used to work with people who decided that Existing conditions could be nominal, one generic material, etc. There were always problems with it, where walls joined up, where dimensions werent accurate, where detailers in CD's didnt *know* what stuff was, and then had to go back to old archived drawings to figure out what something REAL was.... Why deal with that? You have to model existing conditions anyway, its just as fast to model it correctly as it is to model it incorrectly. Its the same wall tool.

If you want it to SHOW as a single generic layer, Phase Filter Graphical Overrides do it just fine.

So what do you do during field verification to document existing construction? Especially older stuff where construction isn't typical studs and 5/8" gyp? Measure face to face, and extrapolate the invisible stuff?

Also, I would love to hear from anyone who does do nominal modeling and why. And also anyone who used to and changed their approach.

FWIW, I once fabricated a wall caliper, that would quickly give me wall thickness, but it only worked at doors. Getting exterior stuff was more work if there was a wall type with no door in it. And that was in the Acad days.

Gordon

Well if you DONT know what the item is, thats a different story. Then i model it as generic, but our Generic Wall Types are also a ridiculous neon color to WARN people that we DONT know what it is. At some point, if something has to join/connect/abutt to it, youll need to know the actual sizes, and youll get it through some sort of field verification.

At my first revit office we DID the thing where we modeled Existing as Generic and undetermined, and it bit me hugely in the ass, when it turned out there was a bunch of structural steel LAYERS on top of one another (three rows of structural framing back to back to build up the wall), and that there were *surprise* columns inside them. What was worse? We HAD documentation for it, but the team said *we model existing this way,* and so because of that... We had to jump around it all in CA. Pointless, when we had built the existing model on day one.

Was similar issues when i did residential work in New York. If you dont know what it is, how can you plan on altering it? You mark it as UNKNOWN, and you have someone drill a hole, or remove a piece, and digure out what it is. When you know, you update it, and do things right.

I'll model it right and be done with it, having done it both ways.

Well, since you are already debating this on forum..

For me it kind of depends on the situation. Basic principle: if it's in any way going to change, then I'll model it in full glory. If not, it's generic. If I don't know if something is going to change yet, I'll go Generic and take the risk of having to redo it.
With that I have a very big and clear sort of legend thingy stating that all solid grey building elements are NOT shown in their as-built form and shape but that it's a schematic representation due to the fact that the actual construction is unknown or unrelevant at the point in time where the documents were created. All changes must be ok'd by me, and so on...

Things I do "cheat" with:
- Curtain walls for existing doors and windows, just to get the basic look in Existing Phase.
- I use face based opening families for new openings in system families (breakthroughs of walls, roofs, floors, and so on). The Opening tool sucks big time since it's not Phase aware.

I've been doing residential remodeling on wood frame construction forever. Here's what I've learned.

1. Generic - Typically I don't use generic walls in any phase. I suppose it doesn't really matter, but I find it easier to make the best assumption and change later as needed.
2. Existing walls - Depending on the complexity or sophistication of the project, I typically don't get too carried away with exact wall thickness dimensions. On most existing older homes, everything is out of square anyways, so I have to assume a decent tolerance for all dimensions. Because of that, it just isn't worth it to be exact on wall thickness. I even assume there is plywood sheathing when I know there isn't, just to keep it simpler when aligning new walls later so I don't end up with the 1/2" bump in the wall line. BUT, I am aware of this when I dimension later, using +/- and making note of the INTENT of what is to align new to existing, ie studs vs finish alignment. The INTENT note is critical as there are too many variables in the field (physical and people) to rely simply on a dimension string.
3. Existing walls in much older homes - On these homes, I'll check all the walls, as there is usually many varying thicknesses. I make a time vs benefit decision on how accurate to be. Usually I show the variation unless minor, like 1/2" or less.
4. Remodeled existing wall with interior finish change - if it's interior, this is typically strip and put back gyp bd, so sometimes it gets thinner if there was existing plaster. I've decided it's not worth the effort in most cases to model the change.
5. Remodeled existing walls with exterior finish change - This is another value judgment. Sometimes I just rely on the paint tool. Other times I'll demo the entire wall. I do this by having 3 phases - existing, demo, new. The changed wall is demo'd in the NEW phase so it just disappears. If the removed portion is brick or stone, I'll model this stuff as a separate wall which can demo'd properly.

If I had multiple staff working on the project, I might approach it differently but with just myself I can make an effort vs benefit decision. It's usually not worth a big effort or focus as the dimensions of the existing are all going to be slightly wrong or off anyways.

This probably should be another discussion thread: On new construction, and sometimes on a new portion of a remodeled project, I am the opposite by being extremely obsessive compulsive about accuracy of the model. 1/2" vs 5/8" gyp is important, as is interior shear ply, wall tile, stone. But when I dimension the new stuff (always to stud and/or concrete), there is another value judgment to make. The guys in the field need tolerance as nothing is ever exact, even in new construction. I'd rather make the decision of where the variable is to go rather than them, if a string of dimensions has critical parts, so I'll put in +/- or holes in strings elsewhere in the non-critical areas. It depends on the design of the house what to do, but the guys in the field will rarely ask but rather just make it work out.

Thanks guys, just the kind of insights I was looking for. I also am of the opinion that modeling it right 9as right as you know) is always best. But of course those who are new to Revit will push back on that. Verification that those actively doing the work are having success doing it "right" is good amo.

Thanks,
Gordon

Anyone using Parts and Phasing? I was waiting for that feature to split layers of an existing wall to demo the interior ones and I am having some issues with visibility at the time I am placing a new wall and join it(to cut with exsg windows). It does not display where there is a part demolished. like masking the new furring wall. Thanks

Most of what we do is residential additions/renovations here in NY. I have wall styles for existing & new, with ex being less detailed. I also like to print with phasing set to New/Previous, and previous has a greyscale.

A big help in establishing existing conditions was buying a laser measuring device - invaluable, in fact. I have a Leica Disto.

We do a ton of remodel work and the tolerance varies quite a bit from project to project. As others have mentioned - the older the property the more room for error there is in measurements. Plaster & Lathe walls have a lot more variance than GWB in the overall thickness of the assembly just like nominal studs as opposed to old studs that are actually 2x4. Frequently we can't knock a hole in a wall to find out what is actually in it and we have to guess. In those instances dimensions are pulled from the finish face of existing to whatever new work we need. I have run into enough odd conditions however that if I can put a hole in a wall I do. We have found chases where there shouldn't be, columns completely off the grid buried in a wall, bathrooms that have been closed off completely, random plumbing and so forth. Usually these aren't picked up until demo starts and we deal with it as the issues come up. In all honesty I don't see much difference in wood vs metal framing when it comes to the random factor. I've seen as much jacked up metal construction as I have wood.

Our geneal workflow is to either get existing drawings and model from them, or in the absence of drawings a field survey and frequently both. Once we have the survey information everything is input into Revit / CAD and we go from there. As our Revit implementation is still new we haven't done any remodel work yet but everything that can be modeled correctly will be. In ACA all of our walls were nominal sizes and we have argued back and forth for several years about it. I'm sure seeing all those 1/8" dimensions in a drawing is giving my boss an anneurism but he'll get over it eventually. For existing work it isn't the worst thing ever but like Aaron mentioned it can come back to bite you and has, although nothing as dramatic as what he ran into.

edit - a laser for survey's is a WONDERFUL tool! By far the best $100 I've ever spent. I liked the one I bought so much I didn't even turn in the receipt and kept it for myself I have the Stanley Fat Max. It's simple but works very well up to about 100'

If the contractor is onboard early on it is a lot easier to fix issues as they pop up since we can have a dialogue through the entire process instead of just after CD's are issued. Some contractors we work with are actually even competent enough to know how to fix things so they fall within design intent without all the headaches of change orders but we work with them a lot.

If you want to ask specific questions on anything feel free to drop me an email or a PM and I'll get you my number.

I'm also interested in your caliper. I hate trying to figure out how thick a wall is. I know for guitar building you can buy one with a magnet in it but it only works up to 8mm and is pretty pricey...