Sugarhouse Foundation Ideas

[Sweetrun]

Starting to build a new sugarhouse for a small operation with a 2X6 evap. Looking for input on using a footing/foundation wall approach vs. a slab foundation. Pouring a slab over a fairly deep stone/gravel sub-base with a thickened perimeter might be an option, and would be less cost. Soils are not well drained (Champlain Valley). Foot print is in the 12’x16’/14’x16’ range. Any thoughts would be appreciated.

[Thompson's Tree Farm]

Just completed mine. I'm north of the Adirondacks on heavy clay soils. I used a base of crushed marble (cheapest available stuff here) a minimum of 4" thick (on the bed rock) and 6" other places. Under the walls it is a minimum of a foot. We left the edges so that when we poured the slab, there would be a minimum of 12" of concrete under the walls. Minimum thickness of the floor is 4". This design was planned, overseen, and most of the concrete work done by my 82 year old father in law who did concrete work for a living in such conditions for 30+ years. Thank heaven for a knowledge base.
Doug

[Sweetrun]

Thompson's,

Thanks for the reply. Sounds similar to the direction I think we are heading. Plenty of stone and a thickened slab at the walls.

[DOlson]

Sweetrun, I do excavation work in northwestern WI. We do a lot of slabs with thickened edges for small buildings and garages. In this area on a site with heavy soil I always strip all the top soil and put in a one foot sand lift. Just make sure the water drains away from the building well. Good luck with your new sugar house! Just cleared the trees for my sugar house today, I am also going to make a slab with a thickened edge.

Derrick

[mapleack]

Several years ago we started remodeling our sugarhouse, I say starting because as you know its never done. When we started part of the floor was concrete, under our old 2x8 and the rest was brick. We were moving up to a 3x10, but decided that some day we might want as big as a 4x10. To this end, we figured out where we wanted the new arch to be in the sugarhouse, then dug a 3 ft deep, 1 ft wide rectangular footer with outside dimensions of 4' by 12'. The center "floor" portion of this footer ended up being 6 inches thick. I also buried an 1.5inch conduit into the center footer for power for forced draft and autodrawoff, etc. A week after the footer was poored we did the rest of the floor around the footer 4 inches thick. Even though there was at least 6 inches of gravel and good drainage under the floor portion, it has moved about a half an inch up and down. The footer portion hasn't moved at all. The new arch got leveled once three years ago, it's still level. Yes, it cost more to do it that way, but I will NEVER have to worry about the arch being level, and I've planned ahead in case I add enough taps to want a bigger arch. As I said, it is more expensive, but from experience, even the best poured slab is going to move. Good luck!
~ Andy

[Thompson's Tree Farm]

Sweetrun,
In my new sugar house I framed and formed out the portion of the floor for the evaporator. The evaporator area has about a foot of fill over bedrock. After the initial pour had cured I poured a 6" pad for the evaporator to sit on. I am hoping that if the main floor shifts, the evaporator base won't.

[farmerEd]

Are you guys just pouring a floor in an existing building that is already supported by some other means? or are you actually pouring a slab and building the structure on top of that?

I've heard of these "floating slabs", but the drill of always going below the frost line (48" in my area), is so ingrained in my pysche, that I just can see how a slab above the frost line won't move.

I could see it for a sidewalk, or even a pool apron, but isn't it risky to support a structure on a slab that is very likely to move?

I am not saying that you guys are wrong, I want someone to explain why I am wrong...preferably oneof you that has a 10-20-30 year track record that this construction method would actually work...I'd MUCH rather do a slab on grade for my outbuildings - if I could only convince myself that they would stand the test of time...

[farmerEd]

A related question...

Is there any reason that the edges need to be thicker than the rest of the slab? What I am getting at is that where I am, the minimum load size for concrete exceeds what I need for a small outbuilding...I could actually pour the whole slab at 12" thick instead of just the edges with the minimum load...for no additional cost. To me that seems like a no-brainer, but am curious if there is a design reason that the slab is thinner than the edge, or is it, as I suspect, just a more judicious use of concrete?

[Haynes Forest Products]

I think what is happening is all this talk about the weight of evaporators has everyone thinking over kill. If you were to lay down a nice bed of road base,riprap,gravel or any other meterial and level it you would have a good foundation for your concrete floor. They say that it not a matter of IF your slab will crack but a matter of when and then the kicker his how bad. If you have a good base,proper rebar, and thick enough concrete you can park a semi on it. A full 3x10 evaporator does not weight as much as a VW so why do people think they need more than a 4" slab? My sap shack and kitchen is on slabs with a thickend perimeter and rebar and it has small hairline cracks but no seperation. I think wisc. has both hot and cold weather and no heaving if it moves it all moves this a good thing. Is your detached garage not (A) out building and is it not on a slab?

[OGDENS SUGAR BUSH]

FARMER ED

the thicker cement around the outer perimiter is usually for a rat wall. keeps critters from tunelling underneath

RICH

[WESTVIRGINIAMAPLER]

I poured a 24" wide x 8 to 12 inches thick footer and then laid up cinderblocks and poured a 5 to 6" pad against the cinderblocks several courses up and have gravel under the concrete. Frost seldom goes below 12" here and my footer is now 3' or more underground due to backfill. In NE, with the deep frost, I don't think it would be a good idea to build a building on just a concrete slab unless it was something small like a 8x12 building/shed. Never built anything up there, but I have heard the Horror stories of what the frost upheaval with do.

Never a problem here for the most part unless you do something stupid when you build.

[Grade "A"]

the reason for the out side of the slab being thicker is that it is the footing for the walls that sit above it, just like you would want to dig out a deeper hole under where a post would go. On a car garage we dig 12" to 18" in and 8" to 10" down from top of slab and the middle is 4" thick. Pouring 12" of concrete will work but I feel it is overkill and gravel is cheaper then Concrete. The key to have it stay together and not busting apart is having drains under the slab. Dirt does not freeze, the water in the dirt freezes so the less water under there the better.

[Thompson's Tree Farm]

My Father in law has been using this method for well over 30 years. He refers to it as an "Alaskan Slab" if that means anything. I agree that drainage is key!!
Our old sugar house was built on a slab poured directly on leveled dirt (clay loam) with no artificial drainage. It heaved and broke but we had made fault lines to control where the fractures would be. Re leveled the evaporator every year but the change was usually less than 1/2 inch. I poured a slightly thicker slab for the evaporator in my new building mostly to limit the amount of bending while stoking the fire, not for additional support. I also put 4 drainage tile under a 26' wide building and 2 more down the sides. I hope that was overkill.
Doug

[peacemaker]

Most cold-climate building codes require you to place foundation footings below the frost line. That can be 3- to 4-feet deep in the northeastern United States. The goal is to protect foundations from frost heaving. There is an exception to this standard: many codes permit foundations to lie above the frost line as long as they're "protected from frost." However, approval depends on local code officials, and may require special engineering. The 1995 edition of the Council of American Building Officials (CABO) One and Two-Family Dwelling Code may simplify life for builders and code officials alike. The CABO code, which serves as the basis for the country's other three model codes, includes simplified guidelines for building slab-on-grade homes with shallow foundations that are protected from frost by rigid foam insulation.

The technology cited by CABO-called the Frost Protected Shallow Foundation (FPSF)-not only saves energy, but slashes construction costs as well. FPSFs can be used beneath heated or unheated buildings. The technology itself is nothing new. It has been used in Scandinavia for more than 40 years (where it's now standard practice), and the National Association of Home Builders (NAHB) has aggressively promoted it in the U.S. for more than a decade. An FPSF often improves the energy efficiency of a typical home, because it requires more foundation insulation than many codes. (The exceptions are states with especially strong energy codes, like Washington and Oregon.)

How It Works
The concept is simple. Instead of placing footings below the frost line, the FPSF uses insulation and drainage techniques to raise the frost line to just below the surface. "We basically make the footings think they're in Florida," quips Bill Eich, a builder from Spirit Lake Iowa, and a nationally known proponent of the system. Even in the coldest climates, this permits footing depths as shallow as 12 inches.

Compressive strength is an important characteristic for these below-grade applications. Compressive strength is related to foam density. Extruded polystyrene used for sheathing above-grade walls is typically 1.5 pounds per cubic foot (pcf). Naturally, foundation applications require stouter material. CABO permits 2.0 pcf extruded polystyrene for horizontal insulation and 2.0 pcf extruded or expanded polystyrene for vertical insulation. The compressive strength of 2 pcf extruded is 40 pounds per square inch (psi) or 3600 pounds per square foot (psf). This exceeds the underlying soil's bearing capacity of around 2500 psf. If you prefer a margin of safety, higher density foams are available.

Designing Good Drainage
Insulation is only half the equation. The other half is drainage and moisture control. To keep surface water from soaking in around the foundation, all roof runoff must be directed away from the house. This means putting effective gutters all around the building and sloping the final grade away from the foundation at least 5 inches in the first 10 feet. (That's 1/2 inch per foot.) To protect the footing from subterranean water, it must bear on at least 4 inches of a non frost-susceptible material such as washed gravel or rock.

Tests Prove Efficiency
NAHB confirmed the system's efficiency by placing test probes around five homes in Vermont, Iowa, North Dakota and Alaska. Instruments recorded ground, foundation, slab, indoor and outdoor temperatures. The insulated footings kept the soil above freezing even in the coldest weather. When probes that Eich buried three feet below uninsulated ground measured temperatures below freezing, those at the base of nearby shallow foundations checked in at 37°F to 40°F.

A Win/Win System
An FPSF can benefit both builder and homeowner. Shallow foundation ditches are easier to work around. The FPSF uses less concrete than a 4-foot deep stemwall. Smaller ditches require less backfill material and the backfill settles less over time. Since a shallow ditch is less likely to disturb root systems, you can leave shade trees closer to the house. (Eich has built within three feet of large trees.)

Eich credits FPSF's with saving an average of $1500 in construction costs for a typical home. "Even homes with full basements usually have walkout portions or attached garages," he notes, "so we routinely plan on a shallow foundation for everything we do."

The technology has even made some customers reconsider what they want in a house. In Eich's market, everyone used to build full basements, since the footing had to go down 4 feet anyway. Now he finds more people building larger homes on the main level and forgetting about the basement. In a 131-unit Denver, Colorado, housing project, the U.S. Department of Housing and Urban Development was able to save $3000 per unit by substituting traditional stem walls with FPSFs. NAHB estimates that, given a realistic market penetration, the system could save nearly $300 million in annual construction costs.



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How does insulation stop frost heave from occurring?
"Frost heave can only occur when all the following three conditions are present: 1) the soil is frost susceptible, 2) sufficient moisture is available (soil is above approximately 80 percent saturation) and 3) subfreezing temperatures are penetrating the soil. Removing one of these factors will negate the possibility of frost damage.

"Insulation as required in this design guide will prevent underlying soil from freezing. (An inch of polystyrene insulation, R-4.5, has an equivalent R-value of about 4 feet of soil on average.) The use of insulation is particularly effective on a building foundation for several reasons. First, heat loss is minimized while storing and directing heat into the foundation's soil-not out through the vertical face of the foundation wall. Second, horizontal insulation projecting outward will shed moisture away from the foundation further minimizing the risk of frost damage. Finally, because of the insulation, the frost line will rise as it approaches the foundation. Since frost heave forces act perpendicular to the frost line, heave forces, if present, will act in a horizontal direction and not upwards."

-Source: Design Guide for Frost-Protected Shallow Foundations, National Association of Home Builders, 1995.



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In a heated building, the frost protected shallow foundation (FPSF) relies on heat from the house to raise soil temperatures around the foundation. One layer of insulation covers the outside face of the foundation, while a second extends horizontally away from it. The rigid foam traps any heat that the ground absorbs from the building, keeping soil temperatures around the footing above freezing. The building's heating system can be safely turned off for a three week period in the winter because thermal lag in the concrete will maintain the soil temperature above freezing.
The vertical foam also protects the foundation wall from "ad freezing." Ad freezing occurs when expansive soils freeze to the outside of a foundation. In some cases, this can heave a foundation whose footing is below the frost line.
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In a standard uninsulated foundation the footing must be buried deep below the frost line.

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[Pete S]

The thickened slab at the building perimeter is to support the weight of the building. Often times, building size dependant, this "grade beam" has 2-#4 rods running through it to add additional strength.

Even though you're slab doesn't appear to be too awful large, consider some post pour "control joints" to be installed.

This will not disallow cracks, just simply "controls' them.

If you pour a solid 12" thick,..................don't water it up too much, as then when the excess water leaves,..........shrinkage may occur.

Just some thoughts.

Pete

[tessiersfarm]

A floating slab is just that. The slab does move but it is strong enough to move as a unit.

A frost protected slab should not move although They still may under certain situations.

I just went to a service call on a building in the portland area that has cracking drywall. It is 160'x220' and has in fact moved 10" in the lowest corner. No structural damage was found. We spent several days on sight with several engineers and found everything to be within designed tollarances. It is a frost protected floating slab that is doing its job perfectly.

a 4" slab with a 12" thickened haunch will easily support the average sugar shack and evaporator. Your garage slab is likely 4" and I would be quite surprised if your evaporator even full weighs as much as a pickup.