why is my subfloor height above terrain negative?

[LeeDrafter]

Hello,

I'm working on the attached plan which is a tri-level home on a sloped terrain. I have defined the middle level floor height as absolute zero and have adjusted the other floors from there. I have made my terrain with elevation data. But I don't know how my terrain elevation (subfloor height above terrain) relates to the floor plan absolute zero. By trial and error adjusting the height until it looked about right, I ended up with a subfloor height above terrain of -40", but that doesn't make logical sense to me. On a sloped lot, which part of the terrain is this height referring to? I'd like to be able to adjust my terrain height in relation to my plan absolute zero, but maybe they are not relational? Thanks in advance! 

tri level Modern 2.zip

[SHCanada2]

you have a terrain point midway on the left at -151

 

for a reference point I took a measurement from that to the patio slab which is at -14in (aboslute elevation)to the top, or put another way, its top is 14" below the top of your subfloor. My measurement from top of slab to roughly where that elevation point is (I took a cross section at the elevation point marker): is about 109 inches. the elevation point should then be 40+14+109, 163, but its only 151..interesting

 

you can also double check the elevation of that point(below) by looking at the toolbar. Mine shows z at -123, which would be 109+14

 

 

I did switch the terrain to  skirt of 2" and follows terrain to take these measurents. I never use the Flat skirt personnally

 

 

 

That said, Essentially your terrain point is putting the terrain at -151" below the terrain reference point. And because your intended main floor to terrain is less that 151 you have to raise the terrain above the main floor (which would be a negative number for the "subfloor height above terrain"))

 

 

 

 

 

 

A question would be, where does the -151 for the terrain point come from and what is it's reference, sea level? something else?

 

 

Edited 23 hours ago by SHCanada2

[SHCanada2]

note your current side elevation shows the rear patio slab floating above the terrain. Personally I would use a terrain region to flatten that area out, if you are permitted to change the grade

 

Edited yesterday at 02:04 AM by SHCanada2

[LeeDrafter]

Thank you @SH_Canada2! That makes a lot of sense that those negative numbers in the terrain elevation points are causing the unusual heights for the subfloor above terrain. I got those numbers from my field measurements in relation to my laser instrument height, so nothing related to sea level. I can change the numbers as long as they stay the same in relation to each other. I'm going to try to fix them so zero matches the absolute zero of the plan and see if that helps. Thanks again!

[LeeDrafter]

16 hours ago, SHCanada2 said:

note your current side elevation shows the rear patio slab floating above the terrain. Personally I would use a terrain region to flatten that area out, if you are permitted to change the grade

 

 

Thanks, and I agree. This is a work in progress, and I will be adding a few flat areas after I get my heights figured out

[SHCanada2]

20 minutes ago, LeeDrafter said:

I'm going to try to fix them so zero matches the absolute zero of the plan and see if that helps.

you dont have to as the subfloor above terrain can be adjusted to move everything up or down. .Becuase you are on a sloped lot, the subfloor above terrain would not be accurate all around the house.

In my view, it is not really then required to be "accurate" as it will not be accurate in all places, as such you could just leave your terrain numbers as they are and adjust  the terrain up and down to your liking 

 

In rereading your post, I'm not clear what the ultimate goal is here. You have the 6 elevation points along presumably the PL?, so those presumably cannot be changed. Are you going to then change the CA terrain around the house to accomodate the patio and driveway? If so you probably want to decide on what you want sloped and where before doing a lot of moving around. For instance on the sides, will they slope back to front only, or are they supposed to slope to the PL. If they are suppose to slope to the PL, then the terrain at your house will be higher than your measured elevation. If you try and set your terrain to match  the front and rear of the house before doing that, then you will need to redo as you will be raising the grade at the house to slope away from it

 

Terrain is more of an art than a science, in my view

 

 

 

Edited 7 hours ago by SHCanada2

[LeeDrafter]

4 minutes ago, SHCanada2 said:

you dont have to as the subfloor above terrain can be adjusted to move everything up or down. .Becuase you are on a sloped lot, the subfloor above terrain would not be accurate all around the house.

In my view, it is not really then required to be "accurate" as it will not be accurate in all places, as such you could just leave your terrain numbers as they are and adjust  the terrain up and down to your liking 

 

 

 

 

Yes, I suppose you're right. That's how I have done it in the past when using this method from my own elevation data. On this, job, I was trying to be very accurate, but I'm sure if the terrain height is within a few inches of accuracy, it will work out fine during construction. I can probably just eyeball it so it looks about right. 

 

On another note, I'm trying to mimic what you showed dimensioning to those terrain elevation points in an elevation view, but I don't know how to see those points in elevation view. I have the layers turned on, what am I missing? Thank you!

[SHCanada2]

8 minutes ago, LeeDrafter said:

I'm trying to mimic what you showed dimensioning to those terrain elevation points in an elevation view

 

I measured on your plot plan from the back of the house to your elevation point on the side, then on the elevation, I drew a dimension from left to right to where that was. Then I just dimensioned from the patio down using my pointer cross hairs(where I thought it would be on the terrain) and CA dropped a marker. I then changed the marker to a level line so it was obvious and moved it to the amount away from the wall (that I measured from the plan view) to the point where it intersected the terrain, and moved it up and down a little until it was in the centre. the other way to do it is to put in a small terrain object where your elevation point is, and ensure the layer is on in plan and elevation view

Edited 7 hours ago by SHCanada2

[LeeDrafter]

13 minutes ago, SHCanada2 said:

 

I measured on your plot plan from the back of the house to your elevation point on the side, then on the elevation, I drew a dimension from left to right to where that was. Then I just dimensioned from the patio down using my pointer cross hairs(where I thought it would be on the terrain) and CA dropped a marker. I then changed the marker to a level line so it was obvious and moved it to the amount away from the wall (that I measured from the plan view) to the point where it intersected the terrain, and moved it up and down a little until it was in the centre. the other way to do it is to put in a small terrain object where your elevation point is, and ensure the layer is on in plan and elevation view

Thank you! good to know there's no way to see the actual elevation point in camera view.

[SHCanada2]

3 hours ago, LeeDrafter said:

Thank you! good to know there's no way to see the actual elevation point in camera view.

none that I know off. Awhile ago, I put a request in the suggestions to have an object be able to be put on the plot plan and be at the top of the terrain, and be able to show the elevation at that location in its label, and for the same object to show on the elevation as well.