How to excavate trench in gravel when foam is above?
David McNeely| Posted inGBA Pro Helpon
New slab on grade in Zone 4A:
I plan to have about 8” of compacted 1/2” crushed stone (no fines) with 2” of XPS sheet foam, then poly of course, then 4” slab. I will need to have two trenches of a thickened-slab type footer for bearing walls.
我担心的是，当我在碎石的岩石中挖掘沟渠时，一些砾石将从片状泡沫下面落下，然后将悬垂。如果薄片泡沫的一些唇部不受支持，我担心两件事：首先，当倾倒页脚时，纸张可以提升;并且，在其从沟槽的底部转换到泡沫的顶部的多个聚合物将在泡沫的唇部下产生腔。
这些问题中的任何一个有效吗？如果是这样，是否有建议的解决方案？
我附上了一个问题，也是一个提出的解决方案。还是我太担心了？
Thanks.
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解决方案详细绘图在等级光束下显示2“XPS - 您是否完成了数学以知道XPS将支持房屋的重量？
由于泡沫压缩，当房屋的全部重量比在邻近等级光束附近的4“部分的小型不支撑的袋时，可能更加担心泡沫压缩。在2“泡沫上的平板无处可适用，距离距离梁部分的房屋的重量附近。
The drawing also shows no XPS on the sides of the grade beam, only CMU, which creates a thermal bridge. At the very least the exterior side CMU should have some foam between the CMU and the grade beam, but doing it on both sides would be even better.
它很好（甚至优选）将Poly完全延伸到等级梁下以限制地面水分转移到边缘处的板坯。
Why XPS instead of more environmentally friendly EPS?
David: have you already placed the foundation footings? If not, why not form the interior bearing wall footings with 2x lumber and do them when you do the foundation footings? I'm with Dana on making sure you insulate under the entire footing.
Use reclaimed xps if available.
首先，确保解决方案是您的混凝土承包商对的东西。我怀疑他们会这样做。级梁基础是棘手的，因为不良好的方形边缘以防止。我认为你最好的是让挖掘机挖浅直边缘沟槽，安装你的60 psi泡沫（确保通过建筑检查员批准），然后你可以在脚边安装泡沫，现在你准备好了级地板，安装泡沫的平衡。
这种方法的唯一垮台是它需要两次倒。
Stephen＆Rick，我正在使用优质墙，抵靠一个碎石的蔓延。他们将首先放置，并且将倒入它们（也用钢捆绑）。我更愿意避免额外的倾注和检查，这将增加我的日程安排。
瑞克，我所提出的解决方案正恰好试图提供自己边缘级梁。
丹娜,谢谢你的建议我版本ify the compression of the XPS. The inspector will likely be questioning me about that. I was relying on this: "Engineers explain that good soils should be able to support 3,000 lbs. per square foot (20.9 psi). As it turns out, common extruded polystyrene (XPS) insulation like Dow Styrofoam or Owens Corning Foamular has a compressive strength of 25 psi." (//m.etiketa4.com/blogs/dept/musings/foam-under-footings）。
RE: why XPS instead of EPS, I just reviewed the discussion in the nearby Q&A thread, and I agree EPS may be the better choice for me (I will definitely have a well-drained slab). In my detail, it would be easy to add foam between the CMUs and the crushed rock.
因此，似乎达人是我所提出的解决方案的否定观点，尽管我还没有听到原因。除了单独倾吐基位，还有其他建议吗？
David,
There may be more conventional or technically elegant solutions but I think yours will work just fine. As others have suggested, I would line the footing sides with foam to eliminate the thermal bridging. If you are worried about that foam moving, you could put it on the outside of the CMUs and add another layer under the whole footing instead.
One other small thing. I'd be inclined to use epoxy and threaded bars instead of anchor bolts. Your concrete finisher will sing your praises for years.
Malcolm，我更喜欢更传统和技术优雅的解决方案！请描述！
这些条件是除了这些加厚的平板基位外，没有其他脚踏穿过建筑物中间的边缘（两个，两人慢跑），因此我不认为单独倾注它们是优雅的。
无论是倾斜还是垂直对我都没关系，我询问TP如何保持压实碎石的侧面或斜坡稳定，安装泡沫，并保持全部不受干扰，而是在一个工程机组人员奠定了多和钢并浇注？碎石将从沟槽下方的几英寸延伸，提供充足的排水。
David,
在我看来，在一定程度上的密集刚性泡沫将起作用，但您应该由工程师和当地建筑部门运行该想法，而不是抓住我的话。
我知道，可以将刚性泡沫安装在倾斜的压碎石上方 - 用于加厚边缘板或您正在计划的基础类型 - 然后是聚乙烯和混凝土，因为我已经完成了。
David,
使用25 psi压缩强度数小心！泡沫数据表指出压缩强度的定义：“屈服的值或10％的偏转，首先发生这种情况。”在随着时间的推移之后，将泡沫蠕动的倾向增加，您意识到您希望远离所述抗压强度。正如马丁斯所说，最好咨询工程师，所以他/她可以浏览数字。
David,
I didn't mean mean to describe your idea pejoratively, just to distinguish it from how a contractor might do the same thing. There are a number of proprietary systems used when making concrete forms out of foam, you might want to look as some of them.
http://www.icfbuildcompany.com/products/the-foothold-icf-footing-ystem/