△ My fence, before and after renovation
In this post I detail how I renovated a 16 year old timber fence to create a slick modern panels that should have a much longer life.
Early in the development of our semi-detached property (c. 2006) we needed to erect a boundary fence to separate our front garden from the neighbour’s which had previously been “open plan”. At the time I went for the cheapest option: timber posts with 6ft x 6ft timber panels in between. It looked really smart when new but was not very durable, as I soon found out…
I quickly learned my lesson when after just a couple of years a storm caused several of the posts to heave, leaving panels flapping wildly. Incredibly, a couple of the posts had actually rotted through and snapped in that short time. Concreted-in timber posts are prone to early failure. In reality, they are unlikely to last more than 5 to 10 years. Undeterred by this early failure, I set about adding concrete spurs which I bolted to the existing posts. Fortunately, the neighbours were kind enough to have these on their side. This was fortunate, as they only had lawn rather than shrubs to navigate, making the installation relatively straight forwards. To further stabilise the long run of panels, I added a top timber rail which spanned across several posts, locking them together into a single unit. The ends of each 5.4m top rail were joined with a crude scarf-joint, creating a single end-to-end rail. This was fixed to the top of each post with a single flanged hex screw and washer. This kept individual posts in line and spread the wind force more evenly across the new concrete spurs. The fence was much sturdier after these modifications and has not suffered storm damage since. The top rail also acted as post-caps, protecting the end grain of each post from rain penetration.
This arrangement worked well for fifteen years, until, in early 2020, I realised that the panels themselves had begun to deteriorate.
In spring 2021, I decided to renovate the fence. Here is a photo of part of the fence from the neighbour’s side. (Fortunately they are not gardeners, so the fence was easy to access.) As you can see, it is in bad shape.
Although the panels needed replacing, it looked as though the spurs, posts and top rail were still in reasonable condition. I hoped I could get away with keeping them. My aim was to create a fence that would last more than another fifteen years. That meant designing panels that would be far more robust and rot-resistant than the originals.
The first step then was to remove the old panels. While dismantling, it became clear that rot had set in mainly on the horizontal rails. Obviously, these were weak points as water running down the panels would always pool there. The other weak point was the gravel boards. These were originally only six inch treated softwood. Being in ground contact, they had quickly succumbed to rot. From here rot had got into the end-grain of the vertical fence boards. Also, being so shallow, leaf mold and mulch added to the soil on my side had in places ended up touching the fence panels. As we shall see, these weak points were eliminated in the new design.
Once the panels were removed, the posts and framework could be assessed. It was really strange looking into my “Woodland Garden” from the other side of the fence! In the picture below, you can see the posts, spurs and top rail that were retained. Also, the woodshed to the right had been renovated in 2020
- See my post: Woodshed Renovation
A new corner post (right, stained black) was installed to allow the fence to extend to the woodshed
One change to the design can be seen in the photo above. This concerned the final (right hand) section of the fence where it joined the recently renovated woodshed. The old fence was dog-legged here, with two 90 degree bends before meeting the woodshed. This was originally done to provide a gate through to the sewage treatment plant (grey-dome far right). The new design removed this dog-leg and gate, replacing it with a single 90 degree corner. This gave me an additional 3ft x 3ft bed inside my woodland garden. The sewage plant can still be accessed from the path behind the woodshed (far-right).
Design of the new fence
To ensure the new fence had the longest possible life a number of longevity features were designed in:
- All timber should be coated with a microporous water-repellant stain.
It had become obvious from other areas in the garden that coated timber lasts much longer than uncoated timber.
- The gravel boards should be 10 inch high Accoya.
Accoya is effectively rot-proof. By making the gravel boards higher, the timber panels above would be held clear of any mulch or rain-splashed dirt.
- There should be no horizontal rails.
Water should be able to run down the panels and not collect anywhere.
- The panels should be a screw-free design.
I had noted several places on the old fence where rot had started at nails or screws. Eliminating these weak-points was a priority.
- Maintenance should be easy.
The panels should be easy to disassemble in the future via easily accessible stainless steel screwed battens.
The design I came up with was to use treated horizontal tongue-and-groove ship-lap boards. These would be stacked one on top of the other, held in slots at each end. This would allow the boards to be secured without any screws or nails penetrating them. The retaining slots would be created by screwing timber battens to the existing posts.
Once the old panels and battens were removed, the posts and concrete spurs were checked. Bolts were tightened and the bottom of each post was cut off to prevent rot travelling up the post from the soil. This allowed the Accoya gravel boards to pass under the posts.
All old timber battens, screws and nails were removed and each post checked for strength and signs of rot.
One post was discovered to have significant rot in the heart and in one side, so it was removed and replaced using an incised treated softwood — a simple task thanks to the concrete spurs and top rail. The concrete spurs provide a cost saving here as the new post only needed to be 1.8m as it was not buried in the ground.
All posts were given two thorough coats of black Barrettine professional preservative wood stain (see below) to enhance their longevity. The concrete spurs were eventually stained as well to make them blend in better.
The top rail showed signs of rot where water had collected in cracks and shakes. However, it had not spread far, and the strength of the wood appeared unaffected. It was decided to give it two thorough coats of preservative stain. The top-rail can be replaced relatively easily in the future if needed.
When looking for timber to make the panels, I knew I would be cutting 6ft lengths – the width of the old panels. Imperial 6ft is not 1.8 metres but 1.828m, i.e. 2,8 cm longer. That made it impossible to use off-the-shelf 1.8m timber. Most timber is sold in multiples of 0.6m lengths. 3.6m lengths were going to be too small to get two 6ft boards out of, but 4.2 m lengths would leave me with large off-cuts. Fortunately, I found a company (Tuin) selling tongue and groove shiplap that came in lengths of 3.9m. This was perfect as each would give me two 6ft boards with minimal waste (8in off-cuts).
SWEDISH T&G SHIPLAP CLADDING – TUIN
Pressure treated Northern Swedish Spruce with an overhanging rebate. This T&G shiplap Cladding is available in Eleven sizes all of which are 18mm thick with lengths ranging from 2.40m up to 5.40m. These timbers have a working width of 13.3cm and are smooth planed.
3.9m lengths: £10.50 per board inc VAT and delivery (Jan 2021)
Each panel required 13 x 6ft boards, or 6.5 x 3.9m lengths (=£69). In total, therefore, the cost of each panel came to under £90 all told, including t&g boards, stain, batten and screws. This is cheaper than most quality t&g (acoustic) panels, and mine will arguably have a longer life and easier long-term maintenance. The Accoya gravel boards cost about £20 each, slightly cheaper (but a lot nicer) than similar sized concrete gravel boards.
Preparing the boards
I cut the boards to length using a chop saw. A simple stop ensured every board was the same length (1.82m). The cut end of each board was treated with preservative by standing the boards on end in a tray of preservative so the end grain would soak it up.
The boards were then stained using a water-repellant preservative stain. I used Barrettine Premier Wood Preserver, Black. I like this product as it is both a water-repelling top-coat, stain and wood preservative all in one. Being spirit based, it soaks in deeply and has great coverage. Note: Barrettine also produce a cheaper product called Barrettine Wood Protective Treatment, but it contains no preservatives and seems to contain less pigment, requiring more coats. I used this for a top coat in places.
As it was February, I carried out the staining in my greenhouse. I used electric heaters to speed up the drying times. Every board was coated on all surfaces: a long job, but necessary to achieve the longest lifespan. Tongues and grooves are weak points where water can collect by capillary action, so ensuring these are well coated was a priority, as they cannot be recoated once the fence is assembled.
Accoya Gravel Boards
The gravel boards were made from 10 in x 1 inch Accoya. These were cut to fit between each pair of posts, and dug into the soil so that their tops were horizontal and level with each other. The exact position was determined by measuring down from the top rail, ensuring all panels were identical.
I gave the top edges of each accoya board 45 degree chamfers to help with water run-off. Three stainless loss-head screws were pre-drilled and inserted into the top of each gravel board which would align with the groove on the bottom board of the panel above. By adjusting how far these screws protruded, the bottom board would be held clear of the Accoya by a few millimetres, allowing air to flow between the two. This was done to prevent the lower t&g board sitting in any puddled water that might accumulate on top of the accoya.
To help hold the bottom board clear of the Accoya, the lower lip was removed from the bottom board as shown here:
Assembling the panels in-situ
Each panel was assembled in-situ. A pair of treated tile battens were screwed to the side of the post, creating a slot which would hold the boards. At one end one of these was left off to enable the boards to be inserted. The fourth tile batten was added once all the boards were in place, locking the boards in without any of them needing to be screwed or nailed.
To fix the battens, all holes were pre-drilled and treated with preservative stain. Stainless steel screws were used with the threads dipped in petroleum jelly to make removal easier. The idea being that the construction is easily reversible should any maintenance be required in the future.
To finish off at the top of the panel, the top board needed to be cut down to fit in the remaining space. To get it in a small (1cm) gap needed to be left between the top board and the top rail. A batten was added on one side to cover this gap. It was screwed upwards into the top-rail. This created a nice visual frame or outline around each pane as you can see in the finished photos.
The finished fence looks smart and modern. It should stand the elements for the next two decades. If minor repairs or modifications are needed these should be straightforwards as the panels can easily be disassembled.