Considerations When Setting Deck and Fence Posts

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Live load on deck post and footing.  Wind load on fence post.
Loads on Deck and Fence Posts

My Fence Guys and NOVA Build Pros are sister fence and deck companies in Northern Virginia and Hampton Roads.  We are your premier contractors for installing your new fence and deck.  However, we are always happy to lend a hand if you prefer to do it yourself.

One common question we get again and again is, “how do we set the posts?”  We’ve heard time and time again about deck failures resulting from sinking posts.  Before the International Building Code was as well known many deck posts were installed like fence posts.  The hole was dug, and post and concrete were installed at the same time.   This may prevent a post from toppling.  However, as you can see from the diagram, the main forces to account for in deck footers is that of the live and dead load.  For the most part, this force is normal (perpendicular) to level ground.  The force must support 40 pounds per square inches.  In general, that means if you divide the square footage of your deck by the number of supporting posts (not accounting for ledger boards) and multiply that number by 40, the result is the weight that the post must support.  Similarly, the footer must also support that weight.  The footer must have a larger bearing area than the bearing area between the post and the footer (i.e. 3.5″ x 3.5″) because the soil load bearing capacity is obviously less than the concrete load bearing capacity.  Concrete bearing capacity is between 3000 and 5000 pounds per square “inch” in general.  The soil bearing capacity is (again, in general) 1500, 2000, or 3000 pounds per square foot.  So… that entire force transmitted through the post (1,000’s of pounds) must be spread across undisturbed earth.  Additionally, the footer bottom should be below the frost level depth.  In our area, footers are typically (check w/ your locality) a minimum of 24″ deep, 18″ square and 8″ thick.  The post can be set in 8″ of concrete on top of that footer, or can be set on post anchors or by other means.  Don’t forget to get your permit(s) and schedule inspections “before” you place the concrete.

For fences, the force that must be resisted is usually due to wind loads (or, kids climbing the fence to retrieve their lacrosse balls).  There isn’t the same risk of the fence settling through the footer.  There is a risk, however, of the fence toppling over due to high winds (or kids, mowers, etc).  This isn’t so much of a problem for decks due to fact that the lateral bracing tends to keep the posts in place vertically.  Fences are essentially cantilever boards (i.e. supported only on one end) sticking out of the ground.  The earth is the only thing preventing them from toppling over in high winds.  So, the larger the cross section of the post (in general) the more the post will be able to resist that moment.  Thus, fence posts should be placed approximately 1/2 to 1/3 in the ground and should be surrounded by concrete as they are set.  Dry packing concrete is a manufacturer-recommended method that helps to speed along the installation.  In a matter of days, the concrete will solidify making removal of the post in tact very difficult.  We always recommend setting gate posts in wet concrete (we use fast setting concrete) so the footer will have a high early strength and be able to withstand the changing forces caused by a swinging gate (or a swinging gate banging against it).

If you need any more pointers or would like us to do it for you, give us a call!


Planning your New Fence

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Paddock or Horse Fence
New Painted Paddock Fence with wire Mesh
Horse Fence
Paddock Fence with Wire Mesh

 

There’s much more to planning and installing a new fence than simply “planting” a couple posts from your local hardware store and nailing boards to them.  To avoid making a costly (or life-threatening) mistake, you should always take the following steps:

  1. Check with your local city planning office to find out what type of fence you are allowed to install.  Most localities publish their fence restrictions online. In general, restrictions are for public safety and usually deal with height and distance from public right of ways.  For example, as shown in the link above, you wouldn’t want your visibility restricted by a fence when approaching an intersection, so some localities don’t allow you to build right up to the corner of your lot even though it is your property.  Violators of these restrictions will be made to move or lower their fence to comply or be faced with a recurring monetary penalty until such a time when the fence is brought into compliance.
  2. Call Miss Utility before you dig.  It’s not just a catchy jingle, it could save your life!  Power and gas lines running to your house are supposed to be 30″ – 36″ deep, which shouldn’t interfere with most fences, but this is not something to bet your life on.  For a number of reasons (e.g. final grading, landscaping, error during installation) these utility lines could be shallower.  You can call 811 to request utility marking on your property.  You can also go online to make a request.  Miss utility will locate and mark all public utilities on your property, usually within 48 hours.  They mark each utility (gas, water, electric, cable) with different color paint.  If you must dig near a marked utility, you should take extra caution and never use a piercing tool like a breaker bar or post hole diggers.  Keep in mind, these markings are only valid for a certain amount of time, usually about 25 days.  If the marks fade, or you suspect your utilities were not marked correctly or at all, you can often request a 3-hour locate from Miss Utility.
  3. Some localities require your new fence to be marked on your plat. Your plat, if you have one, can often be found with all the other real estate documents that you received when you purchased your home.  If you do not have a plat, or can’t find it, a property survey is recommended, especially if you want to build along your property line.  You can either pay the surveyor to construct a new plat from scratch, or, to save money, you can simply ask them to locate your property lines in the vicinity of where your fence will be installed.  A plat (or survey) is need during installation so that your fence ends up in the right place.  The last thing you (or your neighbor) wants is to have to move your fence because it was on your neighbor’s side of the property line.

Find answers to other common questions about fences here.

My Fence Guys is a licensed contractor in the state of Virginia.


How is a Privacy Fence Built?

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Privacy Fence with Lattice
Cedar Fence with Diagonal Lattice on Left. Pressure Treated Pine Fence with Square Lattice on Right.
How to build Privacy Fence with Lattice
Privacy Fence with Lattice

Need a privacy fence with lattice?  Want to know how to build that fence, or any fence?  Take the guesswork out of it!  We have shop drawings for all of our custom fences so you know what you’re getting and how it’s being built.  We find this to be an effective communication tool that reduces confusion and facilitates fence selection.  From the size and length of nail, to the placement of concrete around the post, to the type of cap, width and length of each board and description of options – it’s in there!

 


How to Build a Paddock Fence

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Paddock 4 board, horse fence
Paddock or Horse Fence

Four board, Paddock, Horse Fences are often terms used to describe the fence pictured above.  This fence, particularly when painted, provides a classic look that suits a wide array of properties, ranging from pastures with rolling hills to multi-million dollar homes. A typical paddock fence has three or four horizontal rails made from oak and pressure treated pine posts. These fences can have metal mesh (coated with black pvc) to prevent pets or some critters from getting out/in. Typical mesh has 2″ x 4″ openings. You can replace that mesh with 1″x 2″ mesh that will meet pool code requirements.  Paddock fences are sometimes constructed with 4×4 posts and pressure treated pine rails.  My Fence Guys uses 40 lbs of concrete around each post.  Each post is set 24-30″ deep.  We typically build paddock fence gates from all cedar (2×4 and 1×4).  The cedar is lightweight, strong and doesn’t warp or twist as easily as some other materials.