Contended Insulated Foundation Detail
I’m at the end of my rope here… I’ve been trying to get through the building plan review process for over a year. I had designed what I thought wouldn’t be a strange stem wall and slab foundation (I think a monolithic slab is out because of a 3 foot grade difference?) based on GBA articles on smartly insulated foundations, and really specifically this article from buildingscience.com:https://www.buildingscience.com/documents/insights/bsi-059-slab-happy。
我在第4区，建造一个〜850平方英尺的单层故事。
My plan reviewer (who I’ve heard is notoriously… wrong… but what can I do) said that if I plan on a poured foundation, versus block, it must be engineered. So I sent my structural engineer my foundation plan and asked him to do a design for the stem / foundation wall.
He, in his typical fashion, marveled at why his services were needed, “this is all normal stuff”, and then sent back the black and white drawing attached.
自然而然，它完全忽略了我发送的东西，也没有给平板绝缘等津贴。但是，当被要求修改计划时，他对我非常困惑，他说：“对不起，我无法修改直接从代码簿中获取的标准细节。”
这不是工程师吗？
在短暂的罕见电话中，我们断开了连接的声音，听起来就像他在说，并坚持说：“粉底墙的最小厚度为6英寸”。如果是这样，那么这些建筑科学细节是如何存在的……这似乎是正确的方法，因为它使我无法在基础外部拥有大部分脆弱的暴露泡沫。
I am trying to do this _right_ but feel like I’m doing it so wrong.
Is this foundation detail problematic elsewhere? Has anyone actually built with it?
I’m considering moving the insulation to the exterior of the slab but am concerned about the appearance and durability of a 3 foot tall section of exposed foam.//m.etiketa4.com/article/getting-slab-edge-insulation-right
The “simpler alternative” cantilevered wall there seems like it would set off more alarm bells with the planner also…
Is the only code-approved way to do this just to stick the fragile foam insulation to the outside of your stem wall?
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答复
Tyler,
我不知道您的工程师发生了什么，但是他不必遵循建筑法规中的规定途径 - 这是雇用他的重点。这是I和许多其他建筑商常规使用的相当标准的细节，但是，如果您要获得大量的推动力，也许更容易使用替代方案。除了将绝缘材料移至外部外，还有其他一些：
- Pour the foundation 8" wide and cover the exposed exterior portion with a cap flashing.
- Reduce the foundation to 6" and taper the top of the insulation between the slab and stem-wall so that it isn't exposed.
- 不能在45度的8英寸茎壁的外部降低到顶部5英寸。
Your engineer might mean that he can't change the actual drawing taken from the code book, but he can provide a detail that meets code requirements even if it means creating a new drawing. Assuming you're on the IRC, this section relates to minimum thickness:https://codes.iccsafe.org/content/IRC2018/chapter-4-foundations#IRC2018_Pt03_Ch04_SecR404.1.5.2。它说，混凝土必须至少与上面的框架一样厚。在新建筑上，我通常有10-12英寸厚的双层墙壁，并且与您的建议相似；代码官员和专业工程师，我与所有人一起解释了IRC的要求，意味着混凝土至少需要5 1 1/2“厚，要匹配2x6螺柱，或者有时工程师会让我下降到5英寸的凸起部分。您可能需要从其他工程师开始。
可能还值得指出的是，在这种情况下，茎墙中的“架子”不是为了支撑平板，而是简单地使茎壁厚度与墙壁框架相匹配，因此房屋内部没有裸露的茎墙到创建一个热短。平板完全轴承在压实的填充物上，而不是茎墙。我们喜欢看到茎墙8英寸或更高的厚度，以使其在整个高度上的强度和刚度，但是墙壁轴承的较薄部分不会改变强度。
Tyler,
I have gotten some pushback in the past with this detail, but only in highly engineered homes in seismic zones built on old landslide debris (...I know. I know). The structural & geotechnical engineering explanation for why it wouldn't work was that the slab (along with additional interior strip footings under the slab that tied together footings on opposite sides of the house) was an integral part of the bracing / lateral resistance of the stem walls - essentially the idea was that is there was a seismic shift, the foundation and house would move as one piece. Sort of like a raft slab.
So, it's not unheard of for the detail not to fly... but I figure it's probably safe to assume that these conditions don't apply to your home?
我们过去所做的几乎是马尔科姆所建议的：将绝缘材料移至茎墙的外部（典型的蒙大拿州）。有时我们还会逐渐变细隔热材料的顶部，以便它被板覆盖（尽管在上述地震情况下，我们无法做到这一点）。
很抱歉，如果上面提到了这一点，我没有看到它：您打算让平板成为您的地板吗？如果没有，您只需使用您的工程师 /计划审稿人想要的任何厚度茎墙，将隔热层放入温度休息的边界，将平板倒入它，然后将地板运到泡沫上 - 这样您就可以与外墙框架 +饰面 +底板的厚度无绑在一起以覆盖泡沫。一种方法是运行两层的优势，并将您的终结地板放在上面（基本上是浮动地板）。
You can acccomplish this with block, and it will be just as strong, durable, and constructable as a poured wall.
Use 8" block, and transition to 6" block for the last row. It is 5+5/8, but with a 3/8" parge coat it easily meets requirements, gives you the shelf you need for the insulation, and it's all standard detail that requires no further involvement from engineers.