Announcement

Collapse
No announcement yet.

Standalone 20x24 workshop foundation questions

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Les@Brownsville
    replied
    [QUOTE=geshka;n1237385]WOW, thanks for the responses, folks.

    @Egon . I do want to meet local building code, though I don't have to. I am in rural area with no neighbors close to me or other constructions, so I am a bit relaxed in this


    even if if you are in a rural area, if your building is more than 108 sq feet, most if not all jurisdictions require that you obtain a building permit from your local municipality and they do require that you comply with the building code.

    Leave a comment:


  • geshka
    replied
    @guitarchitect Basically it was two recommendations that was already outlined here - 1. Concrete slab on grade (different thickness and some variations of perimeter depth) 2. Concrete floor on concrete piles.
    I am more inclined to go for concrete monolithic slab with thickened edges. Just need to figure out dimensions - how thick is the main part, how thick is section under walls.

    @John Bartley It is a bedrock somewhere 8 feet down - I don't believe i need to excavate that deep? Also, if i will form a channel around foundation with weeping pipe - it is not clear to were pump excess of water, I will accept any ideas
    Last edited by geshka; 05-17-2019, 08:17 PM.

    Leave a comment:


  • John Bartley
    replied
    Any chance to excavate deep enough with a drain to a low point to remove the water at least from under the shop area? If you can do that and refill with clear stone and weeper pipes then you should be able to get rid of the freeze/thaw movement?

    Leave a comment:


  • guitarchitect
    replied
    Hm, having read about the issues more in-depth with your latest post, I'm not sure what the best approach for you is! The good thing about a monolithic slab is that you can design it to be big, heavy and solid, which means when it moves it's moving together... but the problems you describe with the existing shop suggest your clay is very expansive, and i'm not sure that any kind of pile system would get you a different result... if it's an expansive clay problem then it doesn't matter if it's below the frost line - you need your piles to go down below the clay (which may not even be possible.) Even precast floor sections will be prone to lifting and shifting out of plane and I don't know if they give you any benefit over poured-in-place if you go with an at-grade approach. To be honest I would contact Legalett, explain your situation and give them your geotechnical report if you have one, and see what they say. Even if you don't use them, they may give you advise which you can carry through to your eventual project.

    When I was working in ottawa I knew someone who worked on a house on along the ottawa river, and the hydrostatic uplift pressure was so high in the basement that their floor slab was about a meter thick. Most people would forget about the basement but where there's a will there's a way I guess!

    You never did mention - what was the advice you have received so far? You said it was conflicting but what was recommended?

    Leave a comment:


  • Egon
    replied
    Precast floor sections are a good idea.

    Leave a comment:


  • John Bartley
    replied
    Originally posted by geshka View Post

    I am done with piles, sorry. I need stable and flat floor that will withstand 1.5 ton milling machine and non-wobbling surface grinder. Some of my lighter stuff is on casters, so I will be able to roll it away
    May I suggest screw piles, with a poured concrete floor supported on the piles? If you place the screw piles well below the frost line and form the floor to be poured off the ground, you should have a complete solution? Alternatively, pre-cast floor sections, set onto the piles? A friend built his house like this near Dunrobin. It worked very well.

    Just a thought ....

    Leave a comment:


  • geshka
    replied
    Originally posted by Egon View Post
    build above grade with concrete piles set below the frost level.
    I am done with piles, sorry. I need stable and flat floor that will withstand 1.5 ton milling machine and non-wobbling surface grinder. Some of my lighter stuff is on casters, so I will be able to roll it away

    Leave a comment:


  • Egon
    replied
    If winter water frost heave is an issue build above grade with concrete piles set below the frost level.

    Leave a comment:


  • geshka
    replied
    Originally posted by stotto View Post

    What could you have done to improve on existing shop with concrete piles ( maybe screw piles) and wood floor?
    I leveled floor every year jacking it and putting shims. One time I had to cut off concrete post in the middle as it was risen after winter. I am not screwing my floor panels to the joists as I need to get down every spring and re-level it. I have my posts on depth 4.5 feet down and about 1 feet above ground. Nevertheless, this spring posts are leaning sideways and making my floor crooked again. Also - I started to do some metalworking and brought heavy lathe and milling machine, which , of course contributed to the problem.

    I probably had it enough.

    I have several quotes from 7K up to 12K for the excavation , grade and concrete.

    BTW -if somebody knows decent concrete foundation contractor in Ottawa area, I will be happy to continue shopping.

    Leave a comment:


  • guitarchitect
    replied
    Originally posted by dave_k View Post
    It calls for "compacted sand" ... sand doesn't compact, unlike gravel which is graded, sand particles are of uniform size .... they won't compact. Run a plate packer over it and it only displaces the sand. I've worked with sand under rigid insulation building ice pads for arenas, getting the sand flat and level so your insulation sits flat is by far harder than placing and finishing the concrete. I guarantee by the time you get your wire mesh in the sand will look nothing like the dwg and have filled in your drop footings. In theory it's a good idea but not in practice.
    I get what you're saying but - it is indeed compactable. There's a big difference between sand that has been dumped in place, and sand that has been compacted. Once compacted, construction sand has very high compressive strength (it is coarse), much more than typical sand (like beach or desert sand, which is fine and rounded) which wouldn't hold a footprint.

    Leave a comment:


  • stotto
    replied
    Following original post and not trying to derail thread.

    What could you have done to improve on existing shop with concrete piles ( maybe screw piles) and wood floor?

    You say it's not holding larger machines and is sinking.

    Are your concrete piles actually moving? If so, how deep and how big around?

    Are joists 16" on center? 10" or 12" ?

    What size/ply beams?



    If floor was beefed up and maybe screw piles ( instead of concrete) used it may be a much less expensive venture than a slab. Or not.

    Concrete pricing out west has gotten ridiculous but have no idea what it costs out your way.

    I'll follow post with curiousity as I was also planning on building a shop this year ( or having a small modular built and set on site) but the property owners we were talking with decided not to sell.

    My thought ( and I'll ask the same questions to OP ) was why spend thousands of dollars on concrete?



    I'm far from expert in this area so very interested in the many experienced folks on here chiming in.
    Last edited by stotto; 05-17-2019, 11:04 AM.

    Leave a comment:


  • dave_k
    replied
    Originally posted by guitarchitect View Post
    That's a lot of info so let me know if you have any questions!
    Great post and I realize that the section detail you included was simply for illustrative purposes however I have a few minor issues with this detail

    It calls for "compacted sand" ... sand doesn't compact, unlike gravel which is graded, sand particles are of uniform size .... they won't compact. Run a plate packer over it and it only displaces the sand. I've worked with sand under rigid insulation building ice pads for arenas, getting the sand flat and level so your insulation sits flat is by far harder than placing and finishing the concrete. I guarantee by the time you get your wire mesh in the sand will look nothing like the dwg and have filled in your drop footings. In theory it's a good idea but not in practice.

    I would also add a third bar on top along the line of the anchor bolts and extend the gravel base a foot or more beyond the base of the footing for stability. This is academic really because this type of foundation has to be designed by an engineer.

    Leave a comment:


  • guitarchitect
    replied
    Originally posted by geshka View Post
    WOW, thanks for the responses, folks.

    @Egon . I do want to meet local building code, though I don't have to. I am rural area with no neighbors close to me or other constructions, so I am a bit relaxed in this regard.

    @guitarchitect . Thanks a ton for the detailed answer. Few more questions if you don't mind: Shed that I am planning to build will have no heating at winter (it is actually three season shop) . Will it change anything (from frost heave perspective) in your proposed method of building foundation? Water right now is 2 feet deep from surface level - very high... and it is like that every spring and fall Should I use sump pump or there are other solutions?

    Thanks.
    Gene.
    I designed mine as an unheated building - that's why it has the insulation fully under the slab and it sits on a drainage layer. My shop isn't "heated" per se, but i try to keep it slightly above freezing and around 10C during project time. If you're going the horizontal FPSF route (which I would be tempted to do - i think you get into dodgy territory putting frost/pony walls in when the water is that high), you would want to put your horizontal insulation on a minimum of 6" of compacted gravel (maybe 12"), and the gravel under the monolithic slab in my scheme I would say should be more like 12". Again though it's worth discussing with your geotechnical guy to figure out if the soil has too much clay to allow something like a soakaway to work. In some clay-heavy soils digging a hole is like putting in a pool - if water gets in it stays there. In that case you have to pump it out + away.

    Remember that the water level is the water level no matter where your foundation is. If you dig a hole to 1'10" and your water is at it's highest at 2', it's not getting in. If you build frost walls below the water line, you now have to manage and deal with *all* of the water from 2' down to 5', both between the walls and outside of them, and you may need to deal with water movement as well. With a properly drained monolithic slab-on-grade you are doing your best to keep the building above the water, and the drainage layers help ensure that any water that does get in will be encouraged away. The intent of the FPSF insulation under the building is partly to ensure that any water remaining won't actually freeze before it gets away, and the wings help ensure that the freezing is pushed as far away from the building as possible.

    I have to issue a caveat though to say that I've never done a FPSF in an area with water that high, so I don't know what the best approach is. To be clear it will never eliminate heaving - the idea is just to keep any frost movement away from the building. You definitely want to try to work with a contractor who has done it before, because the local climate partly dictates the amount of insulation.

    Leave a comment:


  • geshka
    replied
    WOW, thanks for the responses, folks.

    @Egon . I do want to meet local building code, though I don't have to. I am in rural area with no neighbors close to me or other constructions, so I am a bit relaxed in this regard.

    @guitarchitect . Thanks a ton for the detailed answer. Few more questions if you don't mind: Shed that I am planning to build will have no heating at winter (it is actually three season shop) . Will it change anything (from frost heave perspective) in your proposed method of building foundation? Water right now is 2 feet deep from surface level - very high... and it is like that every spring and fall Should I use sump pump or there are other solutions?

    Thanks.
    Gene.
    Last edited by geshka; 05-17-2019, 04:06 PM.

    Leave a comment:


  • Egon
    replied
    Will you have to meet any local codes?

    Leave a comment:

Working...
X