Will my coop sink? (New to this)

[Bammy]

We just set posts for our 14 x 14 chicken coop today. Here in central PA we have a frost concern. We dug 9 holes with a posthole digger, inserted an 8" diameter concrete form, filled it with Sacrete and inserted a bolt. One in the back left is sticking out of the ground about 2 inches where the opposite one is out about 10". This leveled the foundation which will be 4x4 treated wood and 2x6 stringers with a plywood decking. Hope this makes sense.

 

[maplesky7]

I'm in northern Il. and we have some pretty cold winters.

I have a free floating front porch that my parents used to have wood framed and screened and later invested into getting glass sliding doors in metal frames.

I can tell you that anything that is free floating, meaning not anchored down... will heave and how with the earth during freezes and thaws... just the way pot holes are born BUT with a free floating structure such as mine... now I have a door that gets stuck and windows that are off track. Thousands + ?? dollars because the roof is tied into it... wasted, in my opinion.

HAD someone explained this to my dad... I'm sure he would have done it the right way in the beginning and when they were tearing the old structure down then they could have started over with the foundation.

I'm not an expert... I was told by a contractor friend when I asked him about my door...

I don't know if this is something you should consider with your coop but I'm at least putting it out there for you to consider.

g

 

[merryberry]

So from all the replies, and what I've been reading online, it seems like life would be much simpler if I could just set the structure on the ground, without worrying about the frostline effects at all.

Unfortunately, I don't think we have an area of our yard that is both a suitable location for the chicken housing and level enough for said housing to just sit upon the ground. Sigh.

 

[merryberry]

I just found some information that is pretty helpful, and I am going to post it here just in case someone is lurking who has the same questions, or does a search on the topic down the road.

http://www.finehomebuilding.com/how-to/articles/firm-foundation-backyard-shed.aspx

On-grade vs. frost-proof foundations

Shed foundations fall into two basic categories: on-grade and frost-proof. On-grade foundations (sometimes called “floating foundations”) sit right on the ground and are sufficient for all but the very largest outbuildings. They’re also the quickest and simplest to build because they don’t require you to dig deep holes or pour concrete footings or piers. On-grade foundations are usually made of pressure-treated lumber or solid-concrete blocks.

Permanent, frost-proof foundations are more difficult to build, but they’re by far the strongest and longest lasting. These types of foundations are designed for cold-weather regions where ground movement caused by freeze/thaw cycles can affect a building.

The best foundation to build for your shed will largely depend on what the building inspector recommends, but keep in mind that it’s often based on three key factors: the shed’s size, the region of the country in which you live, and the type of shed floor you desire.

On-Grade Foundations
It’s no surprise that most sheds are designed to be built with an on-grade foundation. This base is quick and easy to build, relatively inexpensive, and adaptable enough to accommodate all but the most severely sloping sites. In addition, the components are small and light enough to easily set into place and shift around, making it very easy to get everything square and level. Although it’s not technically a “permanent” foundation, an on-grade foundation, when properly built, will probably outlast the shed it supports.

Solid-concrete blocks —
In this type of foundation, the shed is supported by a series of solid-concrete blocks, which are laid out in straight, evenly spaced rows. The number of blocks needed and the spacing between them is determined by the size of the shed and the lumber used for the floor joists.

It’s important to note that you must use only solid-concrete blocks for this type of foundation. Standard wall block or any other hollow block will eventually crack and crumble under the weight of the shed. If you have trouble finding solid blocks at a home center or lumberyard, visit a masonry supplier.

The blocks measure 8 in. wide by 16 in. long and come in 4-in.- and 2-in.-thick units. The thicker blocks are placed first, with the thinner “patio” blocks laid on top when you need to raise one block even with the others. In some cases, you may need to stack two or three 4-in. blocks on top of each other to raise the lowest corner of the foundation so it is even with the highest corner.

If the building site is high and dry, you can set the blocks directly on the ground. However, if there’s any chance that rain runoff will occasionally drain under the shed, you’ll need to use a shovel to remove a patch of grass under each block, compact the soil with a hand tamper, then cover the exposed dirt with 2 in. or 3 in. of gravel before setting the blocks. The gravel bed will ensure that the soil beneath the blocks won’t wash away or become soggy.​

 

[patandchickens]

Frostheave is only a problem if it is uneven. If the whole structure just rides up and down, no biggie (unless of course it is attached to something that *doesn't* move up and down, but that's not relevant here)

So if you can build the coop strongly enough that it cannot flex, it will move as a unit even if the ground gets slightly uneven during heaving, and all will be ok. This requires using all the tricks at your disposal to prevent racking and twisting; thick plywood for the walls, extra diagonal bracing and screwing of things, sturdier wood, good joints, etc. And i would recommend using hinged plexiglass windows rather than sliding glass windows, just in case there is *some* flexure of the coop.

But taking a second look at your original post, given the size of your structure I would not recommend trying it. Also, I am not understanding where the blocks come in -- do you mean to have a raised wooden floor to the whole 'run' portion of the coop? If not, how is the bottom of the mesh walls to be secured?

IMO the simplest and smartest thing to do would be to sink posts into the ground (below frostline) and use those. It doesn't require level ground at all, in fact it is the *easiest* solution to an unlevel site.

Good luck, have fun,

Pat

 

[merryberry]

Quote:
The concrete blocks will (at minimum) sit under each corner of the structure, and possibly under additional points on the frame (we had planned on under each 2x4). Their purpose is to raise the wood up off of the ground and provide a level base to put the frame on. The plan we have purposely avoids using treated lumber (which of course is a debate for another thread).

I think the picture is confusing because I changed the color of the ground inside the run to represent sand. There is no wooden floor, just open ground. The hardware cloth will be secured to each 2x4 all the way around the coop, and either buried into the ground or laid flat apron style like ridgerunner suggested. Does that make sense?

We will definitely have fun. We can't wait to start (although of course it is pouring outside now that we are ready to go!) and whatever direction we take with building this thing, this discussion has helped immensely with making an informed decision. It can be so hard to communicate online, but I feel so lucky to have found such an active and welcoming community.

The best part is that my chickies are coming in just about 2 weeks, and I can't wait!!!

 

[Ridgerunner]

I was responding to your original post and trying to come up with a suggestion that would fit your design. Sinking posts would require some changes to that design. Since you said you were new to building, I wasn't sure how ready you were to look at design changes. There are countless numbers of different ways to accomplish what you are trying to do.

To be honest, I was not thinking about frost heave when I originally replied. After sinking foundations 4 feet deep in Kazahkstan to get below the frost line, I should have. My mistake. Something else I omitted. This structure really does not look all that heavy compared to its surface area in the coop section. I'd have concerns about the wind blowing it off the foundation if it is not secured.

The local conditions do matter as to what you do. Frost heave and erosion are two of the concerns, but you can also get movement depending on the soil type. One example I am very aware of is, if you build on reclaimed marsh land, the soil will shrink if it gets dry, swell if it gets wet, and kind of ooze out from under the foundation if it gets wet under the foundation, especially if it gets some type of cyclic loadings, say due to wind or heavy trucks going by. A friend in the New Orleans area had 22" of differential settlement in their house that had been built on marsh land on what turned out to be a floating foundation. Piling was the correct answer for that foundation. I'm not specifically suggesting that for yours, just giving an example.

The design you have is going to act as one structure. Many designs have the coop and run acting independently but not this one. How much a structure distorts due to deflection is a function of its stiffness. Since this does not have diagonal bracing, the run portion will not be very stiff which means it will distort easily. As long as it does not pull the run apart, that is probably not a big deal. The coop portion will be a lot stiffer which is important because windows and doors can stick. If the coop portion is not firmly fixed to the foundation, the distortion is a function of the stiffness of the construction (materials and construction techniques) and also a matter of time. Wood under stress will distort over tiime. If it were stiff enough, half the supports could just go away and it would not really matter, especially in the short term. Think of an empty cardboard box. If you support it under three corners, it will set there forever without distorting. But if you start filling it with dirt, at some point it can really deflect. Very few of our constructions are stiff enough that this relative distortion would not be a problem. I would not count on it in your case.

If your coop and run is attached to a foundation, then the stiffness of the foundation comes directly into play. If the supports move in relation to each other and your structure, then in addition to the gravity loads (weight) and environmental loads (wind), the relative movement of the supports can add a tremendous load and cause great distortion. Look at it as the stiffness of the entire earth versus the stiffness of your structure. The earth wins every time. So you need to assure the supports do not move relative to each other or your structure. There are different ways do this depending on your specific conditions. Posts in the ground act as piling and can be very effective. Spread footings, like gravel, contained sand, or concrete spread the load into the ground and work well. Some ground is stable enough that just putting the support on top of the ground will work. No one solution is the right solution for everyone. It depends on your local conditions. It's probably the engineer in me, but I have trouble understanding why so many people have trouble accepting or understanding that. Anyway, that is my problem, not yours.

I know I am overanalyzing it and probably boring you with this long discussion. In the end, you are looking for a foundation that does not move relative to your structure above. Many different ways to achieve that.

I don't know if any of this helps you at all. Hope some of it does. Good luck!!!

 

[patandchickens]

If you want to avoid pressure-treated wood, buy 5" or 6" cedar fenceposts from the farm store and use those to sink into the ground. It will work a LOT better than trying to build a run set up on blocks. The unsupported wire on the bottom 8" or so, between the lowest wood and the ground, will be a weak point (and an aggravation to build!), and the chickens will tend to pile dirt up against that wood ANYhow so it WILL be vulnerable to rot.

Good luck, have fun,

Pat

 

[merryberry]

Quote:
No, you are not boring me at all. Truthfully, it is very interesting and helpful, since I am so new to anything related to construction.

I am not married to the current design at all. It is just a starting point. My goals for the design are to get the most efficient use of space, and have something that is structurally sound but not overbuilt (and of course, I want it to be esthetically pleasing as well). I'm not against sinking 4x4's 36" into the ground if that is really what is needed; just trying to understand why and if it is really needed. DH and I are getting conflicting opinions from the people around us, all of whom have experience with building in our soil conditions. I would like to call the building inspector and ask, but truthfully I don't want to alert the building inspector that he should be watching my backyard...

I'm sure you weren't thinking about the frostline because that wasn't the issue I raised in my post. My friend was very focused on a sinking coop, not on the issues that frost heaving raises, so that's what I was initially most concerned about. But this thread has raised my awareness of several other important issues.

I definitely had the concern about the coop being heavier on one side, but I hadn't thought much about the wind at all. And I should, because we have had multiple storms in the last year with winds and wind gusts approaching tropical storm strength. That alone is enough to convince us to sink posts and go more heavy-duty than what we were originally planning.

Thanks so much for the time you've spent replying to me.

 

[merryberry]

Quote:
Its a side note at this point, since the wind issue alone has convinced us that we need to sink posts, but according to the Garden Coop plan that we purchased, there would only be about 3" of space between the lowest wood and the ground because the blocks are supposed to be partially dug into the ground. And I don't think the treated 4x4's bother us all that much; it was just how the original plan was designed. Thanks for your help!