When installing a vinyl fence, specific posts may require reinforcement, such as: corner posts, end posts, gate posts, and perhaps inline posts within a long stretch of fence. It is important to select a reinforcement method that will ensure the longevity of the fence.
Most manufacturers do NOT recommend supplying the potential reinforcement needs of a vinyl fence post with a wood insert. Pine, fir, cedar and even pressure-treated lumber are all subject to water saturation and dry rot when confined within a vinyl fence post. If a post requires reinforcement, manufacturers recommend metal inserts or concrete with rebar.
Several additional considerations are defined below with regard to wood inserts. In fact, wood inserts can be so problematic, other reinforcement alternatives, though more costly or labor intensive, could save you time and money.
The Nemesis for Wood Fence Posts: Water
Even when a post hole is carefully prepped with a 6” gravel base–to maximize drainage and aeration, there are many variables that may still cause water saturation issues, such as: clay, high-water table, dense compact soil, bedrock, cold region permafrost layers–to name a few. Bottom line, adequate drainage and aeration cannot be guaranteed even with proper drainage and aeration foresite.
Rain Gutter Affect
Due to the general design and assembly of a vinyl fence, it will be naturally exposed to high amounts of water through rain, landscape watering, and dew accumulation. The horizontal rails that receive the pickets will also receive the water. Water will then inevitably drain into the vinyl post. Needless to say, it is likely that the posts will constantly receive and accumulate large amounts of water.
Wood: A Beautiful Natural Wonder
By its very nature, wood has very high structural strength qualities. It has the ability to receive and to be exposed to water. Then, it can shed the water, air-out, and retain its strength for years. Even thick posts have this magical capability. Truly, the light-weight strength and resilience of wood is a natural phenomena.
For a Wood Post to Stand the Test of Time, It Must Avoid Water Saturation
If the soil in which a wood post is installed has a high tendency to store water, the wood cannot aerate–the bottom of the post absorbs water and does not have a root system to reroute and whisk away excess moisture and alleviate itself from saturation.
The post can become susceptible to insect infestation, microbes, mold and bacteria which can cause irreparable damage, buckling and decay to the post’s subsurface.
Some species of wood have higher concentrations of natural tannins that repel threats to its structural tenacity. Other building materials composed of wood are intentionally injected with chemicals to provide a similar form of resistance. To build a structure with a prolonged life span, these products are commonly used for a plethora of outdoor structures.
A wood fence without a vinyl sleeve cover and assembled with resilient wood products–especially if installed with proper post hole drainage and aeration forsite–can beautifully withstand the elements for years.
Vinyl Posts Diminish Wood’s Natural Ability to Aerate
As mentioned above, wood inserts within a vinyl post are prevented from proper aeration. Vinyl posts are impervious to water seepage and are made of a similar PVC material that is used to run water supply systems. A vinyl post creates a complete enclosure around a wood insert and disallows it from airing-out along its vertical axis because of the tight fitting environment.
Waterproofing Wood Post Inserts: A Good Intention for Rot Prevention
A wood insert’s only hope of aeration is from the very bottom of the vinyl fence post. Even if proper post installation guidelines are followed, and, even if 6 inches of gravel is embedded into the bottom of the post hole, proper drainage and aeration may only be facilitated for only a short amount of time.
As vinyl fence rails continue to accumulate and drain water inside the vinyl post and into the gravel base layer, in a very short amount of time, small granules of dirt, clay, sand and debris may eventually clog the overall drainage system inside the posthole.
Waterproofing the bottom of a wood insert–reducing water saturation risks–may improve the longevity of the wooden post’s capacity to provide structural support. There are many different methods used to attempt to seal the end of a post: water-resistant concrete, paint, caulk, wood glue, tar, shrink wrap, hot dip, plastic cover. . .to name a few. These preventative measures add time and expense to a vinyl fence install. Some of these methods work better than others. . .none of them are guaranteed to prevent water absorption. Wood, being porous by nature, may accumulate water from anywhere along the post.
Needless to say, aeration and drainage may be impossible to accomplish if the soil conditions aren’t just right. And, waterproofing the entire subsurface of a wood post may be an attempted measure to reduce water saturation–but it definitely isn’t a guaranteed measure of prevention.
Wood Inserts May be Required by the Manufacturer for Preassembled Vinyl Fencing
Typically, the only vinyl fencing product that requires wood inserts into every vinyl post, are preassembled products purchased at local major retailers. These products use a vinyl post sleeve, a thinner walled material, to surround the wood post insert. Subsequently, the post sleeve is not designed to carry the fence load without the wood insert’s reinforcement.
Not only are these wood inserts going to be subject to the drainage and aeration issues mentioned above, they are preassembled products and are connected with a bracket system that is very time consuming to install. Inevitably, in some circumstances, these products may be a suitable solution for your vinyl fencing needs.
However, depending on your project, there are definitely product alternatives that are made from a higher strength composition and are much easier to install.
How to Reinforce Vinyl Fence Posts? The Best Support is Woodless
Manufacturers design their vinyl fence material to be the (arguably) longest lasting and maintenance free perimeter fence solution. They have a vested interest in your fence outlasting any other fencing option. Some vinyl fence manufacturers provide a lifetime guarantee on their products.
Vinyl fence variations are offered with different raw material compositions and slightly different thicknesses. Manufacturer installation instructions will provide guidance as to which posts, if any, will need to be reinforced and what reinforcement methods are preferred. Generally, post reinforcement is only a small portion of the overall cost of the project. However, installing the appropriate reinforcement method is critical to obtain the long-lasting potential that the manufacturer designed the fence to attain.
When is Support Needed for Vinyl Fence Posts? Or, Is it Even Needed at all?
Vinyl fencing is actually a very strong material in and of itself. As manufacturers suggest, installing vinyl posts into concrete may be the only reinforcement that most of the posts will need. However, as recommended, some posts definitely benefit from additional reinforcement.
- End, or Terminal posts: These posts fall at the end of a particular line of fencing and may need reinforcement to provide the core upright strength for the rest of the line.
- *The short 2 ½ to 3 foot double/triple rail decorative ranch style fence may be an exception.
- Gate posts: These posts carry an extra heavy load and are under constant impact and duress.
- Corner Posts: These posts will receive the wind and additional stresses from multiple directions and may need additional support for the converging fence lines.
- Inline Posts Along Extended Fence Lines: Long fence lines may need additional support as they carry an extended amount of exposure to wind–especially with privacy fences that may act as a sort of sale or wind trap.
- Other Unique Property Specific Challenges: Varying property related reinforcement needs may be necessary as identified through careful analysis.
Knowing the Proper Vinyl Fence Installation Method is Critical
Because of the structural design of vinyl fencing, as elaborated above regarding water drainage and enclosure issues, reinforcement does not lend itself to traditional wood fence installation or reinforcement procedures. Typically, vinyl fences are properly reinforced with the methods listed below:
- Metal Sleeve: a steel or aluminum sleeve is inserted into the vinyl. This is the absolute easiest and time saving method of reinforcement.
- Pros: So easy. Relatively lightweight. Comes in several different designs depending on the location and the connection of the posts (inline, corner, or end). Comes with full-length options and half-length options (for inline posts).
- Cons: Expensive. $60 to $90 for full-length inserts, $30 to $60 for half-length inserts . (However, make sure and wage a cost vs. labor analysis before selecting other alternatives.)
- Concrete and Rebar: As an alternative to the metal sleeve, manufacturers may recommend adding a full or half fill of concrete inside the post with a couple lengths of rebar.
- This option is more laborious than the metal sleeve. However, if simultaneously installed in succession with all of the other posts needing reinforcement, it could be a way to save on the overall install.
- Thicker and/or Unique Fence Material: Some manufactures have designed thicker posts which do not need reinforcement. Others have manufactured the post’s composite material with additives that increase strength without increasing the volume giving it more stability and limiting the additional reinforcement needs that other products may have.
- Spacing: This is a personal favorite installation method of mine. Consider finding a vinyl fencing product designed to install the posts closer together. For example, installing the posts 6’ on-center, instead of 8’. Personally, I love the aesthetics of 6’ spacing far more than 8’ spacing.
- With this method, extended fencelines will naturally have more stability.
- It may require installing a few extra posts with the overall install. But, it may not require you to add support to inline posts in high-wind areas.
- Check with your manufacturer for specs to determine if this is a viable option.
Get Advice From a Pro
Good luck with your vinyl install. The project will lend itself to many end-result benefits. However, installing a vinyl fence really is a lot of really, really hard work. See my post here for other things to consider with your project. And, as always, be sure and seek advice. Perhaps, obtain three or four bids from local contractors. Ask lots of specific questions relating to your personal project and, please, pay them for their time if you find value in their contributions. Their suggestions could save you a lot of time and a lot of money with your install.