# Thread: Floor Slab - Flat Bottom Sloped Top

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## Floor Slab - Flat Bottom Sloped Top

Is there anyway of making a floor slab that has a constant, even, flat bottom face (that's easy enough) but with a sloped top. For example, a slab that starts as a 200mm thick and slopes / tapers down to 150mm thick.

I know I could probably create one slab, apply a slope to it and then use an in place family extrusion for the remaining part (very fidly). Is it possible to make as one complete slab so my quantities are correct?

Any help would be great.

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## Re: Floor Slab - Flat Bottom Sloped Top

Easy, just tick 'Variable' under Structure for the Type Properties.

You can then edit points and the bottom will stay flat.

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## Re: Floor Slab - Flat Bottom Sloped Top

Hey there,

In a word...yes.
They added a feature in RAC2008 which allows you to set one of your materials to have a variable thickness. In the case of a concrete slab, it would be just this material.
(Edit the structure within the elements type)

You can also edit it later to be as simple or complicated as you want.

Good luck and hope this helped.
Steve

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## Re: Floor Slab - Flat Bottom Sloped Top

I have a elevated concrete slab that is going on the back of a residence over pan decking. The slab needs a constant slope of 1/8"/12" from the house. The block walls and pan decking are one consistant height, so the slab will taper. I can do this by modifying the points of the slab, the problem is, the slab turns corners, takes different angles, etc., leaving me to do the math to define every single point created from a corner or change of direction. This is not only tedious, but it results in connecting valley lines from misc. points no matter how many decimals I use in the point definition.

This would be tolerable if the only thing I wanted to accomplish is creating the slope of the slab, but we are now at the stage where we would like to start splitting the face of this slab to define borders, stamp pattern etc., and unfortunatley, every valley created in the slab now has it's own triangular face when using the split face tool.

I can create the slab with one slope defining line to get my constant slope and no valley lines, but then my concrete layer will not stay variable.

Does anyone have a smoother work-around for this situation? It would be nice when modifying the points of the slab to have the ability to select one line, offset that one line and tell the other points to adjust accordingly, working similar to defining a sketch line to define slope, that way I could get the slab to taper, have a constant slope and still have one solid face with no valley lines to modify with the split face tool.

Josh

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## Re: Floor Slab - Flat Bottom Sloped Top

I know what you mean. I had the same problem. Mine was simply resolved using a few reference planes in different views. I then snapped the slab points to these reference planes. Where you have more than one turn it can get very tedious.

Another option maybe to create the slab as a single square covering the entire area, assign the slope you want as a variable and then using the opening tool to cut the areas where there will be no slab. I'm not sure if this will work, I don't even know if the opening tool can be applied to floors?? Just an idea.

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