# Swapping Structural Foundation Slabs with Iso Footings

**URL:** <https://forum.dynamobim.com/t/swapping-structural-foundation-slabs-with-iso-footings/5292>\
**Category:** Revit\
**Tags:** revit\
**Created:** [July 29, 2016, 6:44am UTC](https://forum.dynamobim.com/t/swapping-structural-foundation-slabs-with-iso-footings/5292 "2016-07-29T06:44:27Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Rooney\_Wayne](https://avatars.discourse-cdn.com/v4/letter/r/8e7dd6/32.png) [@Rooney\_Wayne](https://forum.dynamobim.com/u/Rooney_Wayne)\
**Post date:** [July 29, 2016, 6:44am UTC](https://forum.dynamobim.com/t/swapping-structural-foundation-slabs-with-iso-footings/5292/1 "2016-07-29T06:44:27Z")

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HI,

Is there a way we can swap out a foundation slab with the same dimensions to a ISO footings or any structural foundations(generic Models). because in Revit we cannot swap it directly. I tried extracting point geometry using topology faces and placed the family instance but not quite there. It places the family in all the points.

Can anyone please give some ideas??

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**Author:** ![Alisder\_Brown](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/alisder_brown/32/14995_2.png) [@Alisder\_Brown](https://forum.dynamobim.com/u/Alisder_Brown)\
**Post date:** [July 29, 2016, 8:48am UTC](https://forum.dynamobim.com/t/swapping-structural-foundation-slabs-with-iso-footings/5292/2 "2016-07-29T08:48:50Z")

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@Rooney_Wayne  
Im sure there will be a more elegant way of acheiving this. But give the below definition a try. You will need to have Archi Lab package for the delete node used.  
You need to put in the Type name off the slabs you want to swap out (incase you dont want to swap all of them) and youll need to make sure the ISO foundations Width, Length & Depth are set to Instance parameters and put their names in the definition. Let me know how you get on.

 ![](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/2X/3/3da46de0edc90382510f11ed3e6db951ee25e495.png)

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<div class="post-metadata">

**Author:** ![Rooney\_Wayne](https://avatars.discourse-cdn.com/v4/letter/r/8e7dd6/32.png) [@Rooney\_Wayne](https://forum.dynamobim.com/u/Rooney_Wayne)\
**Post date:** [August 2, 2016, 5:58pm UTC](https://forum.dynamobim.com/t/swapping-structural-foundation-slabs-with-iso-footings/5292/3 "2016-08-02T17:58:13Z")

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@Alisder_Brown the bounding box idea is good. But when the element are at an offset, the point shows the Z elevation but family instance places it at level zero. it’s weird but that’s what happening.

Also is there a way to select the family type by name. the idea is the name of the foundation slab matches a generic structural foundation but with type properties, which means we will create types already and when the name matches the family type it places that respective family. is it possible.

![](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/2X/8/8ea8c54844b493e56db26a92c50ce73ff7c0ec20.jpg)

 ![](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/2X/4/4737a5d8840cb012a69c63d1abed460e5cab5b50.jpg)

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<div class="post-metadata">

**Author:** ![Einar\_Raknes](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/einar_raknes/32/8566_2.png) [@Einar\_Raknes](https://forum.dynamobim.com/u/Einar_Raknes)\
**Post date:** [August 2, 2016, 8:07pm UTC](https://forum.dynamobim.com/t/swapping-structural-foundation-slabs-with-iso-footings/5292/4 "2016-08-02T20:07:27Z")

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Yes this is strange, seems like a bug to me. (Edit: [https://github.com/DynamoDS/Dynamo/issues/6975](https://github.com/DynamoDS/Dynamo/issues/6975))

This is what I get:

##Step 1: Feed the centriod directly  
Looks like the new instance is placed relative to the level it was assigned

 ![](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/2X/c/c2a30dc3e2b04649fc907f783b40124ff4daa1f5.png)

## Step 2: Try to move the centroid to the level elevation

I try to move the point by the levels elevation and gets the same result as in step 1.

 ![](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/2X/6/6b6f64c316a3cfd4a26347005ed059c422d5c24b.png)

##Step 3: Go back to step 1.  
when I reconnect Solid.Centroid to point, I get the expected result.

 ![](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/2X/6/6e46b9ae54059217ccb8f861066d430680c23be8.png)

For the other question about family type by name, did you check the library under Revit \> Family Types?  
 ![](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/2X/8/84e8baea14353cf44ee0350fb49218b4efe7fd93.png)