Can we build on "loam"?
2 study sources mentions "loam"
One says yes we can build on loam (because it is a mix of sand, silt and clay although my understanding clay is not good to build on) and the other says we can not because loam is considered organic.
When researching google, loan can be built on.
Can someone from NCARB clarify please from NCARB point of view and for the purpose of the ARE exams, can we or can't we build on loam?
Thank you
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Hi Yvette,
I don't think you can build on loam. It's topsoil. Anything with clay is going to be unstable. Anything organic is going to decompose, so its volume will diminish.
Silt also isn't a good foundation material, though when it's mixed with sand or gravel is might be ok.
Hope this helps!
Rebekka O'Melia, Registered Architect, NCARB, B. Arch, M. Ed, Step UP, Step UP ARE 5.0 Courses
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Yes, loam can support a building. It is a combination of sand, silt and clay.
Gravel, clay, shale, sand are okay; rock (bedrock, limestone, sandstone) is great for supporting foundations of heavy buildings. But rock is VERY expensive to remove for basements and is overkill and not required to support most buildings.
Organic soil and peat (dark brown or black and easily compressible) are not competent soils. Loam is not prohibitively organic.
Soils with very high clay content can be difficult to build on, but we build on soils with moderate quantities of clay (like loam) all the time. Yes, it swells when wet, but our foundations (generally) are made to account for that as best they can and as long as the foundation rises and lowers consistently, without differential settlement in just one corner of the building, we're usually okay.
If Amber Book is one of the study materials that told you you can't build on loam, let me know where you think you saw that error and I'll be sure to fix that. --Michael Ermann, Amber Book creator
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Thank you both for your responses but that is exactly where my confusion comes from. Owning the concept is that we can not build on organic soil. But some consider loam organic and some don't. This is a white and black answer where NCARB need to step in to clarify. In real life we will follow what the soil report recommends but we are here to pass the exam and get licensed. So contradictions between 2 very reliable and popular study sources like these create confusion and doubts. Actually Amber Book, Mr. Ermann, is the one answering "yes" to this question v.s. Black Spectacles, which is NCARB approved, answer is that we can not build on loam.
Thank you
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I waited a while for NCARB to step in and clarify, but enough time has gone by and since they haven’t, I will… the NCARB approved test prep provider program was phased out this year. When it was in effect, NCARB officials never checked material for accuracy…rather material was “reviewed by an NCARB committee of volunteer architects, who evaluated whether the materials adequately addressed the content areas and objectives outlined in the ARE 5.0 Guidelines.”
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Hi Yvette,
NCARB does not use Black Spectacles or any other third-party test prep to author items for the ARE. Instead, a panel of volunteer licensed architects from around the country, typically 5-10, write, review, and approve items for use on the ARE. This panel typically utilizes the reference books listed on pages 111-116 of the ARE Guidelines when authoring items and developing rationales for the correct response(s). I would reference these books in regard to building on organic soil and loam.
One additional note, you most likely won't get a question on the ARE that simply asks if a building can be constructed on loam or organic soil. The ARE does not contain items that assess whether a candidate can remember factual information about building construction. Instead, you'll be presented with various pieces of information like a soil report, boring logs, geotechnical report, client program, project budget, foundation information, or site plan and be required to make a judgment call based on the provided criteria. There are many variables that will need to be considered when answering a question on the suitability of site soil, so we recommend becoming familiar with common soil types, the challenges/opportunities/impact associated with each, as well as how to evaluate different types of soil and geotechnical reports.
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Hi Yvette - I think that you're referring to a note in our Soil Analysis Virtual Workshop. I just want to clarify that we don't say that you can't build on loam (because you can!), we're simply talking about the relative suitability of soils for construction in that workshop. That doesn't mean the less suitable soils are unbuildable upon, just that they require other measures to be taken (which typically increase cost) in order to build on them. If you think there's another area in our study materials that indicate that you can't build on loam, please get in touch with me and I'll take a look at it!
Thanks NCARB for your note about how this, and other topics, may come up on the exam. We actually write our questions using the same process that NCARB does - a team of architects writes and reviews each item, using the primary NCARB resources listed on pages 111-116 as guidelines. We avoid recall questions and it's comforting to hear that the ARE doesn't feature those types of questions either.
Chris Hopstock RA
Black Spectacles
ARE Community -
At Amber Book we have a different approach. Rather than utilize a panel of architects for technical topics like this, we tap a network of experts to create our content: soils experts, civil engineers, structural engineers, building envelope scientists, lighting engineers, acousticians, wood scientists, code officials, construction lawyers, mechanical engineers, plumbers, electricians, elevator repair technicians, masons, concrete folks, framing & finish carpenters, gutter installers, urban planners, real estate professionals, roofers, steel erectors, cost estimators ….and of course a team of architects.
As discussed above, NCARB exclusively uses volunteer architects to create test items, and we generalists are not as likely to be correct on technical content as the experts. But it seems so unlikely that if NCARB’s architects unknowingly get it wrong on a technical question, that a panel of generalist architects assembled by a test prep provider would get it wrong in the EXACT same way! And if the NCARB architect volunteers get it right (which they usually, but not always, do), we think we’ve taken steps to get it right too. -
Yvette,
As far as the ARE goes, if you see 'loam' as a choice for bearing a foundation, it's not going to be an acceptable choice. "Loam" is sold around here as topsoil, and as the definition below from dictionary.com indicates, it's a humus topsoil. Humus material, clay, organics and peat cannot bear a foundation.
Yes, soil can contain many things - sand, silt, gravel and organic materials, etc. Gravel is your best choice for bearing a foundation, but a mixture of better materials along with small portions of not as good materials can be acceptable. The ARE, I believe, just wants to make sure you know which materials are not acceptable.
Taking measure like compacting poor soil or importing materials to 'fix' poor soils is very expensive, and not always successful, so that's not a great option. And I doubt that'd be presented on the ARE because it's not standard construction.
While it's good you are questioning things, I don't think the circular answers presented here are helpful.
Chapter 21 in Ballast covers soils. You should try to memorize letter symbols of the Unified Soil Classification System on p 21-5, and which materials cannot support a foundation for the ARE - clays, peat, and organics.
Hope this helps!
Rebekka O'Melia, Registered Architect, NCARB, B. Arch, M. Ed, Step UP, Step UP ARE 5.0 Courses
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I think we've gotten away from the topic (building on loam) a bit - but I'll share one last thought on our approach to practice questions at Black Spectacles.
We create questions that match the actual ARE as closely as possible - both in content and in user experience. That's why our whiteboard and calculator function just like the real thing, all of our questions function the same way (including image-based questions), our case studies function like the actual exam, etc. An important part of preparing for the ARE (apart from, obviously, studying) is to practice taking the exam, using something that's as close as possible to the real thing.
Since NCARB's questions are written by a panel of architects, then reviewed by architects and psychometricians - we do the same. In our opinion, the best way to get our questions as close to what you can expect on the ARE is to write them using the same process NCARB does. If NCARB began to have concrete folks, roofers, and gutter installers write their questions we would too, but for now they don't. I personally am glad that's the case - I think architects are perfectly suited to write questions about architecture that test aspiring architect's competence to practice in our profession.
Chris Hopstock RA
Black Spectacles
ARE Community
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