Best Practice: Levels locate top of (a) finished floor or (b) structural slab?

[damon.sidel]

What do you consider best practice for levels?

Is your finished floor at the level or is your structural slab at the level?

Do you set it up differently for different projects/situations?

Whatever you consider best practice, are there exceptions?

If you care to elaborate, what do you consider to be the pros and cons of each choice?

[dhurtubise]

For us it's 99% Finish Floor

[Devin_82]

We tend to have a lot of levels. We have them for TO plate, TO sheathing (slab), and TO fin flr. I have heard some say it shouldn't be a level if it isn't a view, but this is what has worked for us in the past. It causes occasional issues if you aren't paying attention because some objects, walls for example should be on the TO sheathing, but other should be based on the TO fin flr, like the windows. Our views tend to be TO sheathing (or slab), so we have to make sure when we are placing windows that we place them on the correct level.

[damon.sidel]

We tend to have a lot of levels. We have them for TO plate, TO sheathing (slab), and TO fin flr. I have heard some say it shouldn't be a level if it isn't a view, but this is what has worked for us in the past. It causes occasional issues if you aren't paying attention because some objects, walls for example should be on the TO sheathing, but other should be based on the TO fin flr, like the windows. Our views tend to be TO sheathing (or slab), so we have to make sure when we are placing windows that we place them on the correct level.

Sounds confusing! Thank you for the response. :)

[Devin_82]

Sounds confusing! Thank you for the response. :)

Yeah, it can be. But I think that its one of those things that you figure out pretty quick and that becomes pretty easy once you do. Think layers in ACAD, you had to make sure that you were on the right layer when drafting specific elements, now you have to make sure your base constraint is correct when you are modelling different elements.

The beauty of Revit (and sometimes the pain in the butt) is that there is almost always a couple of ways to do something and you get to figure out how to make it work best for you and your project or office.

[patricks]

I would NOT condone only having levels for various views. That makes things a major PITA when it comes to changing heights of something.

For instance maybe you have a Roof Eave Ht level, and your Roof Plan references that level. But then maybe you have a Parapet Ht level which is the top of your wall parapet. That level does not have any views associated with it. But if your parapet height changes, it's a heck of a lot easier to change that than it would be to go around having to change the top offset setting of all your walls, assuming they were all offset above the Roof Eave Ht level. Even worse if you have more than one parapet height.

As for floors, for us the floor level is pretty much ALWAYS the top of the concrete slab or wood subfloor deck. For finish plans we usually place thin 1/8" floors on their own workset that represent carpet, tile, etc. but the level datum itself is to the top of the slab or deck. For roofs it's typically the bottom side of the deck, which usually also coincides with the top of framing.

[jsteinhauer]

Top of Slab, because T.O. Finished Floor is dependent on material being used. I don't want to have 2-10 different levels, one for each material. Not to mention having a sloped floor.

Cheers,
Jeff S.

[david_peterson]

I provide Levels for main floors only. Platforms, Mezzanine...... top of steel.... if I were going to use anything for these little intermediate levels I'd use a named reference plane. But if you use this method you'll have to make sure that you always check what the active work plane is.
Typically I just use top of slab and use the Z-direction offset to move it to the bottom of the slab.

[dkoch]

We call it "finished floor", but the reality is that it is the top of structural slab, for the reason jsteinhauer gave. The actual floor finishes probably are not even known at the time that levels need to be set in the model, and no one is going to track all of the different net heights. Variation in the actual top of slab over the entire floor is likely greater than the delta on most of the flooring we use. Door frames and interior partitions are all going to run from top of slab, typically.

[Devin_82]

We call it "finished floor", but the reality is that it is the top of structural slab

I should clarify, when I said we have TO Sheathing /Slab and TO Fin Flr, those are specific to our project needs. We do a lot of multi-family, Type V and Type III wood structures over concrete podiums with subterranean garages. So TO Fin Flr isn't really the completely finished floor with the carpet or the vinyl or the laminate, rather it is the gypsum underlayment that typically sits on top of the structural sheathing. This is usually in the 1.5" neighborhood, so it is important for us to distinguish between the two datum points for things like interior/exterior partitions and windows or stairs. If we were just talking carpet thickness, then I would agree with everyone above and say its probably not worth it.

[patricks]

I should clarify, when I said we have TO Sheathing /Slab and TO Fin Flr, those are specific to our project needs. We do a lot of multi-family, Type V and Type III wood structures over concrete podiums with subterranean garages. So TO Fin Flr isn't really the completely finished floor with the carpet or the vinyl or the laminate, rather it is the gypsum underlayment that typically sits on top of the structural sheathing. This is usually in the 1.5" neighborhood, so it is important for us to distinguish between the two datum points for things like interior/exterior partitions and windows or stairs. If we were just talking carpet thickness, then I would agree with everyone above and say its probably not worth it.

In that case I would also have my level be the top of the finished "hard" floor, before any finishes are installed. For wood framing I *might* have a level that is the bearing height below the floor, i.e. the top of the stud wall that the floor joists are sitting on. But that would be a level with no plan views associated with it. The top of the finished "hard" floor would be my level with the floor and ceiling plan associated with it.

[damon.sidel]

This is all really interesting. Thank you for all your responses so far.

Here are my thoughts: Revit places floor constructions from the level downward and is set up as a built-up construction. For types of construction that have minimal floor finish thicknesses, like carpet, thin-set tile, resilient flooring, I can understand placing the level at top of structure or subflooring. However, when you have walk-off mats, stone, soundproof construction types, etc., the "finished floor" can be over 100mm/4inches. That requires an extra riser on your stairs. Door frames may be on slab, but the door height will be from finished floor and I'm not recreating doors to have a frame height and a door height, so I'd want doors on the finished floor. Window sill heights are also in reference to the finished floor. We do a lot of floor to ceiling heights where we try to minimize the expression of the frame, so we want to know the offset from finished floor.

For architectural design intent, we ALWAYS want to think of the surface you walk on as a continuous datum. Yes, the top of structure is also a continuous datum (with a few exceptions), but we have to determine that with a negative offset from the finished floor from exterior to interior.

For all of you who use top of structure and consider finished floor thickness as something that varies on top, how do you deal with stairs, doors, windows, ceiling clearances, etc.? Are all you floor finishes so minimal that you don't have to worry about it?

[MikeJarosz]

Interesting to hear the differences of opinion.

Think how these drawing sets look in the contractor's plan room. The school project out for bid used top of slab, with lots of slab depressions for brick pavers. The next project in that same plan room, a mall store fitout, used finish elevation. Then there is the big one, a tower downtown, where they did it a third way. Each architect was certain their's was the right way. The contractor on the other hand, has to deal with them all.

I say it depends on the project, and what it takes to accurately describe the work. I tend to agree however, that finish elevation is messy since the finishes can vary from thick brick pavers, to a simple coat of paint. But finish level makes sense in an existing condition like the mall job. The tower however is a core and shell--- there will be no finish. That's for the tenant to figure out later.

[patricks]

Even worse might be when you have an office using an elevated modular floor with services BETWEEN the structural floor slab and the actual finished floor! Could be a difference of 2, 3, even 4 feet!

In those cases I would have a level datum for both elevations. For something like a 2-story wood-frame building where there is roof framing sitting on an exterior wall, I will have a top-of-framing elevation for my exterior and interior bearing walls to go up to. Then I will have another level 12 to 14" above that for the actual 2nd floor subfloor, which will host the stairs, doors, walls on the 2nd floor, etc.

[damon.sidel]

I tend to agree however, that finish elevation is messy since the finishes can vary from thick brick pavers, to a simple coat of paint.

Isn't that an argument for the level being at the finish elevation? You'd want the top of the brick surface and the painted surface to be at the same level and everything below it might require various offsets. If it was a concrete sub-floor (steel decking with concrete or pure concrete structure), you'd might have a topping slab to make up the difference between the two finishes. Yes, top of structure would probably be constant, but so would the finished floor... so I'm surprised that varying finish floor thickness is an argument for top of structure.

In a wood frame construction with tile, carpet, and wood flooring, I can see keeping the level at the top of the subfloor and letting finished floor thicknesses vary: they are not so different and will probably taken care of with thresholds.

However, the more varied finished floor surfaces, I think one would prefer the level to be at finished floor to assure that the walking surface is consistent throughout... at least on the architectural drawings. For structural and maybe others, it is a different situation.

[Bastiat]

I always dimension to structure. The slab is the structure therefore I would dimensions to the slab. This would also be my FFL (I know it sounds like a contradiction) and anything on top like carpet or a floating timber floor has to be allowed for by doing details of this area if necessary (very unusual that this would be the case).

[dkoch]

I have not done much (any) wood-framed, residential work in my career. Floor construction has been either concrete slabs or, most often, concrete on metal deck. The floor elevation called out is almost always the top of the concrete slab for the majority of the floor. Differences in floor finish thicknesses are handled with transition details, generally involving "flash patching" under the thinner material to provide a smooth transition to a thicker material. Where particularly deep floor finish systems are used (walk-off mats at entrances, ceramic tile and waterproofing system at roll-in showers, etc.), we would, in coordination with the structural engineer, call for a slab depression to eliminate the difference in thickness. In cases where there are extensive areas requiring depression, it may be more cost-effective to keep the top of structural slab level and provide a topping slab in areas not receiving the thicker flooring. For the latter case, we would most likely call out both the top of structural slab and the top of the topping slab. I have not had to do that on a Revit project yet, but I imagine it would be done with a Level, and there just would not be any architectural plan views for the top of structural slab level, but I am open to suggestions on a better way to do that.