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How to fix a wooden fence post
Replacement
Should a fence post be set in concrete?
How much concrete is used to fix in the post
Which fence posts are best?
Wooden posts
What are incised posts?
Concrete posts
Metal posts
Advice

Should fence posts be set in concrete?

  • Light weight fences with spaces in the fence which allow winds to freely blow through has less need of extra support, but timber posts will rot quicker in saturated conditions.
  • Cementing in a fence post gives greater stability to the fence post and improves resistance strain in strong winds from movement.
  • The structural resistance can be increased by enlarging the hole size or by making the hole square shaped which gives a greater surface resistance in the ground when surrounding the post in the hole with cement.
  • The cement should have a smooth declining angle away from timber post to allow water to disperse away from the post. For wooden posts it is best for the cement to be proud of ground level in saturated areas.

How much concrete is used to fix in a fence post?

  • Timber posts should be concreted to the top of the soil level to reduce the wetting area and allowing the timber to keep as dry as possible.
  • Calculating how much post mix depends on the size of the hole and post. A round hole of 175 millimetre wide and 600 millimetres deep, using a 100 millimetres thick post in the centre will require approximately 1.5 bags of post mix per post hole.

How far apart should fence posts be?

  • It is based on your panel size or rail length used which will be 1.8 metres - 3 metres. The more posts there are per metre of fencing, the greater the strength of the fence which also reduces the risk of rails sagging due to the loading weight of the fence boards.
  • The further posts are set apart the greater the load is on the post fixings and rails. A natural product like timber has weak points called knots where it gives little or no stupport the rail, post or paling board. Knots can be large enough to take up more than half the thickness of the rail and for a 3+ metre will become a real weak point.
  • When fence posts exceed 2 metres apart then there should be a centre support attaching the gravel board to the fence paling board. This is done to make sure the paling board stays seated inplace in the interest of keeping the expected uniform look to last the test of time. 
  • Arris rails can be up to 3 metres
  • Cant rails should be 1.8 - 2.4 metres.
  • Square cut timber rails of at least 75 by 45 millimetres can be up to 3 metres between posts. Any greater distance will be a risk of overloading fixings after 5-10 years of weathering.

Which fence posts are best?

  • The best wooden fence posts should be only Hazard Class 4 posts , meaning suitable for ground contact. But, wood used for wooden posts varies pending on suppliers and where they source their type wood species from. Many 15year guarranted wooden posts fail well before a suppliers guarrante period. They will rot as the presservatives used are organic and will be diluted down by the natural weathering elements.
  • The best fence posts to use are concrete fence posts with a selection for most fence styles. But, lightweight posts have become common within fencing suppliers and are much more fragile. The steel supports within the post must not be bearing visibly as they will rust and fracture the posts long term.
  • Stainless steel posts have the best corrosion resistance but are very expensive.
  • Hot dipped galvanised posts have very good lifespan due to a 20 micron coating during the galvanising process but are very expensive. Estimated 50 year durability
  • Folded galvanised posts only has a 4 micron coating during the galvanising process but are still longer lasting than any wooden post. Estimated 25 years durability.
  • Wooden fence posts should be inspected every couple of years for rot.

What type of fence post is best?

  • The best posts are the ones which don't rot.
  • Stainless Steel posts are best but extremly uncommon and extremly expensive.
  • Concrete posts and hot dipped galvanised posts have a simular durability. Folded galvanised steel posts have a shorter lifespan due to only having a 4 micron coating.
  • The best wooden posts are incised posts but even incised fence posts will rot and the longevity varies due the species wood that is used.

What fence post lasts the longest?

  • Concrete or galvanised metal fence posts will last the longest. It will depend on the thickness and quality of each product. Concrete & Hot dipped galvanised steel should both last at least 50+ years.
fence post timber

What timber is best for fence posts?

  • The best ground contact post is a spruce incised post. Spruce wood has a high resin count throughout the timber which reduces water absorbtion. When the spruce has the incised process it allows the preservatives to penertrate deeper into the wood surface.
  • Wooden post failure is likely to be improved by sealing the wooden post 100 millimetres above ground to 150 millimetres below ground level as a minimum precaution. 
  • Fact, wood rots and will fail to support the fence at some point. The best posts to use are concrete post with a life expentencey of between 5-10 times longer than a timber post.
  • A timber post are high maintenance and a cheaper choice for a customer. Concrete or metal post are low maintenance long term with a great longevity.
  • A fence post spur is the recomendation if you desire wooden posts for your fence. The wooden post is bolted to the above ground level of the concrete spur, keeping the wooden post away from constant saturation of ground contact.

What are incised posts?

  • Closely spaced incisions  are made throughout the length of the wooden fence post which allows a consistent absorbtion layer of preservatives during the pressure treatment process.
  • The best wood to use for incised post  is the Heart wood from the Spruce tree. Spruce trees have a high resin count which means it does not absorb moisture well, meaning it should be more durable in wet conditions. Not all incised posts are made using the Spruce tree wood, so check before buying.
  • A hazard class 4 post should be kiln dried to 18% moisture content which enables a higher preservative intake when under pressure which forces the preservatives into the wood grain.
  • Preservatives used are organic water based preservatives. The incisions in the post will hold more preservative and allow a better saturation of the post after the pressure treatment process has finished 
  • Spruce wood does not absorb the preservatives well due to the high resin composite but the incised process allows the preservative to penetrate to a good consistency.
  • All timber has varying porosity throughout and incising the post is the only way to ensure the timber to have a good even protective layer of wood preservative into the wood grain during the pressure treatment process.
  • The slices made during the incised process holds more preservative than standard posts which saturates the 5-10 millimetres layer of the post due to the incising process.
  • The timber used is normally spruce or larch as the timbers has a good durability and absorption of the preservative.
  • Absorbtion rate is consistently even due to the incised process of knife incisions into the length of the wooden surfaces.
  • Has a life expectancy of 12-20 years.
  • Incised posts have a 15+ year guarantee.
  • Incised posts should benefit when adding a protective coating to seal the wood 100mm above ground to 150mm below ground as a minimum.

Redwood fence posts

  • Supposed to have a good resistance to rotting but found very little to prove this. 
  • Have a very good absorption of the wood preservatives with up to 30 millimetres penetration into the timber
  • 15+ years guarantee ( Please read fencing guarranties section at the bottom of the page)
  • Has a life expectancy of 5-10+ years depending on preservative and process
  • Average life expectancy of 7-10years
  • Absorption rate is uneven 1-12 millimetres due to the varying density of the wood.

Pine fence posts

  • Pine is more cohesive with the liquid preservatives as the wood grain is less dense, a lower resin count and absorbs the preservative like a sponge when the process is undertaken correctly.
  • The preservative should penetrate approximately upto 10-15mm into the timber but due to the varying density of the wood it may only absord to 1 millimetre in depth into the wood grain.
  • The main problem with pine is it also absorbs water easily when in saturated conditions and is faster rotting.
  • Have a life expectancy of 2-15 years depending on preservative and process
  • Average life expectancy is 7-10 years but as little as 2 years.
  • Absorption rate is uneven 1-12 millimetres due to the varying density of the wood.

Spruce fence post

  • Spruce absorbs the preservative up to 5mm into the wooden post during the pressure treatment process, but, due to the varying timber structure the preservatives absorb unevenly into the wood and may only penertrate to 1 millimetre. Due to the high resin count it has a better durability to repel water which increases its longevity.  
  • Have a life expectancy of 4-20 years depending on preservative and process.
  • Average life expectancy of a standard pressure treated spruce fence post is 10-15 years but as little as 4 years.
  • Absorption rate is uneven 1-5 millimetres due to the varying density of the wood and high resin count.
broken concrete post

What are concrete posts?

Timber post on a concrete spur

  • A concrete fence post has steel stays inserted in the post before the mortar hardens off. This gives some reinforcement to the post structure. For solid fences the concrete post diametre needs to be 100mm x 100mm for the best longevity of the fence.
  • Concrete slotted light weight posts are approximately 80mm x 95 mm and are only suitable for using retaining panels due to being a weak construction. Ideally concrete posts need to be 100mm x 100mm approximately and the steel stays must not be visible as they will rust and expand which will split open the surrounding concrete of the post.
  • Concrete spurs have the uniqueness of being the only bolt on and off post support for a wooden post. The concrete spur should be positioned in desired position in a hole & cemented in. The wooden post is then bolted securely to the concrete spur with coach bolts, ensuring the wooden post is above soil conditions. Wooden posts longevity is increased using this method by 2-3 times and is simply replaced, without digging out the post, by unbolting the old and bolting on the new wooden post. This gives the longevity of a concrete post and the aesthetics of timber if you can cover up the visible 600mm, knee height, of spur protruding from the ground.

Metal fence posts

Galvanised post

  • A folded steel post has a 4 micron Pre-Galvanised Steel coating and increases the longevity of the steel. Folded steel posts wind tollerance is approximately 100mph. The lifespan is expected to be 30 years+
  • Hot dipped galvanisation is best as it has approximately a 20 microns coating and has a much greater resistance during the salt spray test, and the advised usage for coastal areas as salt air rusts steel quicker.  The life expectancy is 50 years+.
  • Suitable for virtually any type of fence.
  • Some metal posts are light weight and easy to install.
  • Wind Tested to 110mph.

Aluminium post

The slots in the posts keep the chamfered rails securely supported without the need for drilling holes for fixing the rails to the post. The advantages are:

  • Quicker
  • Cheaper
  • Slots for the rails which reduces working time of fixings.
  • No drilling holes meaning the rail should have a greater longevity.
  • Holes on the post to slot the rails into which will give a secure hold of the rail.

Advice

  • Only use concrete, galvanised steel or hazard class 4 wooden fence posts as a ground contact post.
  • Make sure wooden posts have been pressure treated.
  • Ensure timber fence posts are a Hazard class 4, which means suitable for ground contact. Suppliers will offer a warranty of 15-25 years. Keep your reciept.  
  • Check suppliers guarantee as they will have their own terms and conditions which must be adhered to for their guarantee to be valid in some cases.
  • Make sure the post concrete is proud of ground level with a smoothed pitched slope so water will drain away and ensure the timber post will not be in saturated conditions.
  • Treat the timber posts with a good quality timber paint before they fixed securely in the ground.
  • From ground level to 100mm above, should not have nails or screws as this is the wetting zone and is most likely to transmit moisture through to the untreated timber. This is most likely to give a shorter life expectancy to the wood post.
  • Post caps are advisably fitted to the tops of timber posts to reduce weathering. Without a post cap the weak part of the post, which is the end grain where the capillaries are. The capillaries can transmit water into the post, reaching the section of the post, which is untreated, Post caps will help increase the post longevity, slowing the rotting process.

Guarantee

  • Is only valid when the suppliers’ guidelines are followed correctly by the fence contractor
  • Dose not cover replacement installation costs unless the contractor guaranties their work
  • Receipts need to be kept attaining a replacement post which has rotted through during the guarantee period, if you can prove the post was installed correctly.
  • It is best for the customer to purchase the fence materials, so you know you have the receipt and the quality of posts that you require.
  • Businesses only keep reciepts for seven years and a post guarrantee from some suppliers is 15+ years.
How-Which-Fence-Ipswich

Fencing Contractors company in Ipswich, A garden Fences suppliers expert companies Services & constructions builders, unparalleled fence repairs of panels, rails & posts for 23 years

Established in 2002 as M.A.C.C.S Landscapes & experimenting with materials for 10 years to find the best practises & materials to understand why some concrete & many wooden posts fail a 15 year warranty if it has a guarantee. Understanding a product gives the customer the best service which is why we dissect structural materials and supply the findings for people to make informed decisions.


 
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