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Standalone 20x24 workshop foundation questions

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  • iamtooler
    replied
    I would call your gravel crushed stone. Natural small stones (river rock?) has rounded surface so it does not compact well.
    Rob

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  • Beaverfever1988
    replied
    Originally posted by iamtooler View Post

    What does clear gravel mean in your area, and crusher run? We used to use ''pit run'' sand with stones because it was cheap but in the last thirty years new buildings get raised much higher above grade and crushed stone is the only way to go, it will not wash out from under.
    Rob
    Clear gravel is washed stone that is all the same size. It is the stone they used for your weeping tiles. Here's a picture of 3/4 clear.
    Click image for larger version

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    crusher run is stone that is crushed to a size. The designated size is of the largest stones, but contains smaller stones right down to dust. This is 3/4 crusher run. Click image for larger version

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    Here pit run is like you said, sand and gravel. It's literally just something they run into while digging in the pit. Materials from quarries varies alot depending where it came from, and what type of rock is there.

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  • Rusty
    replied
    Originally posted by John Bartley View Post
    The OP hasn't visited for a couple of days. I hope we haven't scared him away.

    There's been some good discussion about what sort of heaving he's getting ... frost, hydraulic, hydrostatic (not looking for an argument about which is which) and possible solutions, but none of us know anything about his lot, where it's located, his proximity to neighbours, available paths for drainage for for routing sump water or weeper piping if he is lucky enough to be able to drain by gravity. I still think it would help to know these things.
    All of those things are extremely important to know. it's also important to understand the construction process which should start with a solid foundation and the reality is you can build anywhere but you may have to prepare to spend a bunch of loot to make an inappropriate site useable. The obvious further reality is you may not want to spend that much money and that's when compromise takes over and quite often the results are less than terrific.

    Good luck to the OP with those decisions.

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  • John Bartley
    replied
    The OP hasn't visited for a couple of days. I hope we haven't scared him away.

    There's been some good discussion about what sort of heaving he's getting ... frost, hydraulic, hydrostatic (not looking for an argument about which is which) and possible solutions, but none of us know anything about his lot, where it's located, his proximity to neighbours, available paths for drainage for for routing sump water or weeper piping if he is lucky enough to be able to drain by gravity. I still think it would help to know these things.

    Leave a comment:


  • iamtooler
    replied
    Originally posted by Beaverfever1988 View Post
    What type of foundation does your house have, how far from the proposed garage is it and is your house foundation having problems?

    Could you post a picture of the area you would like to put the shop? Grading may be the number one solution to your problems.

    I'm not a fan of floating slabs as they're alot of cement and gravel (money) for what you get. Also makes it more difficult to raise grade to stay dry. That being said it would probably be fine and cheapest for you, plus you've got tons of good advise here already.

    If I was doing it I would dig to firm soil as shallow as I could, pour a concrete wall on a footing and raise grade. Without seeing your lot I couldn't tell ya if this would work.

    Also clear gravel would be the best choice for under the pad. It only takes a light tamping (same as sand) to be ready for cement compared to crusher run. Best part is, it keeps your concrete floor from sweating on those hot humid days.

    Good luck with your shop build!
    What does clear gravel mean in your area, and crusher run? We used to use ''pit run'' sand with stones because it was cheap but in the last thirty years new buildings get raised much higher above grade and crushed stone is the only way to go, it will not wash out from under.
    Rob

    Leave a comment:


  • Beaverfever1988
    replied
    What type of foundation does your house have, how far from the proposed garage is it and is your house foundation having problems?

    Could you post a picture of the area you would like to put the shop? Grading may be the number one solution to your problems.

    I'm not a fan of floating slabs as they're alot of cement and gravel (money) for what you get. Also makes it more difficult to raise grade to stay dry. That being said it would probably be fine and cheapest for you, plus you've got tons of good advise here already.

    If I was doing it I would dig to firm soil as shallow as I could, pour a concrete wall on a footing and raise grade. Without seeing your lot I couldn't tell ya if this would work.

    Also clear gravel would be the best choice for under the pad. It only takes a light tamping (same as sand) to be ready for cement compared to crusher run. Best part is, it keeps your concrete floor from sweating on those hot humid days.

    Good luck with your shop build!

    Leave a comment:


  • Egon
    replied
    Pile = pile

    Pier = pier

    They are spelled different.
    Piles come in many different design forms, how they are installed and how they accomplish their load bearing capabilities.

    Leave a comment:


  • dave_k
    replied
    Originally posted by guitarchitect View Post
    We don't study it because of federal projects - typically the government has its own architecture division that does those, although sometimes it gets contracted out.
    So the fed's architectural division doesn't hire Canadian architects?

    Originally posted by guitarchitect View Post
    The exams used to be part of the NCARB system (using the International Building Code) which would let you apply for a license anywhere in north america, but that just didn't fit how people wanted to practice after going to school in canada. So, Canadians have the option of now writing the ExACs which let you apply for a license anywhere in Canada (you're still held to the local body's licensing requirements though so it's not a rubber-stamp process).
    Common issue in Canada. Nursing for example, uses US exams. There was a big debate over it a few years back and there is a problem with Canadian trained nurses failing the exams because of the differences between the US and Canadian systems. The reason for using US exams it's cheaper to buy exams than write them.

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  • dave_k
    replied
    Originally posted by guitarchitect View Post

    I disagree that there's little difference - it's just that the differences are not necessarily related to Part 9. the OBC has an entire section dealing with renovations of existing buildings (part 11) that the NBC doesn't have, note to mention a number of SB's which are unique to provincial policy and direction (energy efficiency for example, which does affect Part 9).
    Lets just back this up a little. This thread is about a guy who is looking for a solution to his foundation problem. In the conversation he states he is looking for a guide to the building code and I suggest the CMHC guide to wood frame construction.

    You say it's no good to him because it's based on the NBC. I say it's close enough ... it hits all the main points which seeing as the provincial codes are based on the NBC makes it a good Canada wide resource.

    So is the guy going to find the answers to his questions in part 11 of the OBC? Nope.

    Does the provincial policy on energy efficiency affect his proposed floating foundations ability to support a 1.5 ton milling machine without that side of the building sinking into the soil making his shop look like a listing oil tanker? Nope.

    What it gives him a good knowledge of what's required by the BC and what he can and cannot do without the help of design professionals. At worst it gives him enough knowledge to ask the right questions of city hall so he can build his shop and start milling metal.

    The CMHC guide has been a great resource for Canadians for generations. As a teaching tool it's main strength over the OBC or NBC is that it's simple, plain language and it's illustrated. This may not be advantageous to architects and engineers but to those visual learners among us and to people who need an overview of Canadian construction standards that lays out the BC requirements without having to wade through legalese it's a godsend.






    Leave a comment:


  • guitarchitect
    replied
    yeah and i even gave him a monolithic slab detail early in the thread too, along with the principles that he probably wants to adhere to no matter what he does.

    not to discount what egon said but it wasn't detailed enough - most people (even many of my architect colleagues) don't know the difference between piles and piers and use the terms interchangably. from what he said it wasn't clear if he was referring to piers (which is what it sounded like) or piles connected to a slab on grade, or friction piles.

    All of that aside, given the sound of the clay and water situation (likely expansive but who knows), I would be wary of piles (unless connected to bedrock) or piers. Friction piles (which is any pile that doesn't go to bedrock) and piers both rely on friction with the soil, and expansive clay with a high shrink-swell capacity will pull away from them over time. Neither are especially good in higher water table conditions because the wetting of the soil reduces friction with the pile.

    Is that to say none of them will work? Of course not - piles are used for large slab-on-grade industrial buildings all the time, and you can't always pick the best site for your building... but you have to design for your needs based on the site condition, and tricky sites need more consideration (an engineer). i also gave geshka a good lead for a company that does slab-on-grade systems and do the engineering as part of the process (they gave me a tonne of free advice that helped me design my monolithic slab), so I think he's well-equipped to make an informed decision at this point.

    Leave a comment:


  • Rusty
    replied
    Originally posted by guitarchitect View Post

    If he wants to solve his problem, it won't happen listening to a bunch of guys on the internet. There are a variety of ways to build something, but to really meet certain performance criteria (such as "I never want it to move out of place") you sometimes need professional help. He's described enough challenges that it's pretty clear he needs to take that path. It's not about passing the buck, it's about recognizing the complexity of the issue.

    OBC/NBC was a tangent - no one referenced it as a way to solve his problem.

    To your question about hydraulic/hydrostatic - Hydraulic pressure deals with hydraulic fluid. Hydrostatic pressure deals with the pressure exerted by a fluid at equilibrium. think of it this way... if you know your water table is at 2' below the surface, that's where it is at equilibrium. if you put your foundation and floor down at 4', hydrostatic pressure is the pressure exerted "up" by the water because it wants to be at equilibrium - at 2'. That's where the "static" part of the phrase comes from. Let it be known that this is just for visualizing it... the actual force at work is gravity, which is exerting a downward force on the water table, so the force "up" by the water is actually equal to the "downward" force of water by gravity, blah blah blah... the deeper you go, the higher the pressure because there's more water weight pushing down, and so on.

    The problem with excavating the problem soil is that (a) he's surrounded by it and who knows how deep it goes, and (b) his water table is at 2' in the spring. i don't think he's in good shape if he digs out say 6' of soil that then holds 4' of water in the spring, whether it's full of gravel or not. The best solution is for him to drill piles down to bedrock (it's only 8' away) and put a slab at grade that will resist the uplift caused by his soil. But how you design that solution (and how much it costs) is beyond the userbase here. If his only problem is frost heaving, a FPSF and a monolithic slab (probably with a beam down the middle in each direction) will solve that easily.
    Now that's a helpful answer. I understand the tangent. It's just not helpfull but you can discuss and argue it's merits for how ever long you want.

    As to a bunch of guys on the internet,,,,some of us are professionals and can describe solutions. Egon described a fix way back at the start of this thread and I have no clue as to wether he's a professional or not but piles were discounted as a poor option and no discussion followed,, when in fact that might be his best option. The point is he needs to be presented with solutions that he can easily understand and assess. I daresay piles were discounted because most of this bunch of guys doesn't know a thing about them or their ability to carry a load when connected to a grade beam.

    Leave a comment:


  • guitarchitect
    replied
    Originally posted by Rusty View Post

    Perhaps an explanation of the difference between hydro static and hydraulic is in order. I'm not interested in an argument it's a discussion to aid the original poster.

    Expansive clays will not lift piles if you are below the clay.

    I agree with Egon. Excavate and eliminate the problem soil or get your foundation below it. Advising of a geotechnical advisor is like buck passing. If you have been in construction long enough you should be aware of certain situations and their cure. I mean no offence, but quoting and depending on the OBC or the NBC by you or any others in this discussion will not answer the questions posed here by the OP.

    I know some people think I'm a bit blunt but you guys really need to decide whether you want answers to your issues or do you want to reference a building code which will not answer anything to do with this OP's question. Yes it's a great idea to follow the building code but the building code does not say " if you have this problem do this!" So I'm just saying to advise the guy to read the code is not helpfull at all. Offer a solution and let's discuss it for him!

    If what he is telling us is true and I have no doubt that it is, I know that I can overcome his issues several ways.
    If he wants to solve his problem, it won't happen listening to a bunch of guys on the internet. There are a variety of ways to build something, but to really meet certain performance criteria (such as "I never want it to move out of place") you sometimes need professional help. He's described enough challenges that it's pretty clear he needs to take that path. It's not about passing the buck, it's about recognizing the complexity of the issue.

    OBC/NBC was a tangent - no one referenced it as a way to solve his problem.

    To your question about hydraulic/hydrostatic - Hydraulic pressure deals with hydraulic fluid. Hydrostatic pressure deals with the pressure exerted by a fluid at equilibrium. think of it this way... if you know your water table is at 2' below the surface, that's where it is at equilibrium. if you put your foundation and floor down at 4', hydrostatic pressure is the pressure exerted "up" by the water because it wants to be at equilibrium - at 2'. That's where the "static" part of the phrase comes from. Let it be known that this is just for visualizing it... the actual force at work is gravity, which is exerting a downward force on the water table, so the force "up" by the water is actually equal to the "downward" force of water by gravity, blah blah blah... the deeper you go, the higher the pressure because there's more water weight pushing down, and so on.

    The problem with excavating the problem soil is that (a) he's surrounded by it and who knows how deep it goes, and (b) his water table is at 2' in the spring. i don't think he's in good shape if he digs out say 6' of soil that then holds 4' of water in the spring, whether it's full of gravel or not. The best solution is for him to drill piles down to bedrock (it's only 8' away) and put a slab at grade that will resist the uplift caused by his soil. But how you design that solution (and how much it costs) is beyond the userbase here. If his only problem is frost heaving, a FPSF and a monolithic slab (probably with a beam down the middle in each direction) will solve that easily.

    Leave a comment:


  • Rusty
    replied
    Originally posted by guitarchitect View Post

    It's hydrostatic pressure that you're referring to, not hydraulic.

    As I've said in a number of posts now it is far more likely that, all things being equal and assuming his last shop wasn't built very poorly, the issues he's seeing are the result of expansive clays, and not hydrostatic pressure alone. Only way to know (and work around it) is a proper soils test and the advise of a structural and geotechnical engineer.
    Perhaps an explanation of the difference between hydro static and hydraulic is in order. I'm not interested in an argument it's a discussion to aid the original poster.

    Expansive clays will not lift piles if you are below the clay.

    I agree with Egon. Excavate and eliminate the problem soil or get your foundation below it. Advising of a geotechnical advisor is like buck passing. If you have been in construction long enough you should be aware of certain situations and their cure. I mean no offence, but quoting and depending on the OBC or the NBC by you or any others in this discussion will not answer the questions posed here by the OP.

    I know some people think I'm a bit blunt but you guys really need to decide whether you want answers to your issues or do you want to reference a building code which will not answer anything to do with this OP's question. Yes it's a great idea to follow the building code but the building code does not say " if you have this problem do this!" So I'm just saying to advise the guy to read the code is not helpfull at all. Offer a solution and let's discuss it for him!

    If what he is telling us is true and I have no doubt that it is, I know that I can overcome his issues several ways.

    Leave a comment:


  • John Bartley
    replied
    I think maybe it would help if we knew a bit more about the area that OP is building in .... urban, suburban, country estate lot, rural? Elevations, grading, ditches nearby?

    I guess what I am getting at is :: can the area be excavated to get rid of the water bearing clay?, replaced with clear stone and weepers below the frost line? Does it have to be a sump pump or can it be gravity from the weepers to a nearby lower elevation?

    Where do you want to build?

    cheers

    Leave a comment:


  • Egon
    replied
    Movement winter - spring sounds like frost heave.

    If piles are out then ecavate material to below to below the frost line and back fill with material that will not support capillary action. Then go for a slab on grade.

    Leave a comment:

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