Garden fence maintenance tips

Getting your fences in good order goes a long way to making the garden more attractive. You can replace them, repair them or even add new sections quite simply and cheaply

For wooden fences to be an asset in a garden, they must be regularly treated with preservative and repaired as soon as damage becomes apparent. Like any cut wood which is exposed to the elements, fences are susceptible to rot and infestation—so unless renovations are conscientiously carried out, they can quickly fall into a state of disrepair.

Preservatives

Most new posts have already been impregnated under pressure with a solvent to protect against wood-boring insects and fungus infections. But if there is any doubt as to whether this is the case, soak the post for at least two days in a preservative before putting it in the ground.

One external wood preservative that can be used is creosote. This has a tar and oil base, and in the UK a brand to BS 144 is recommended for fencing. In Canada, a preservative containing creosote and pentachlorophenol is often used.

The main drawback to creosote is that it stains the wood a dark, not very attractive colour. Also, once the wood has been coated with creosote it cannot normally be painted over.

Creosote must be applied to dry wood—either by soaking or applying with a brush. If you brush it on, bear in mind that it will penetrate only about 3mm into the wood and that the whole process will have to be repeated in a couple of years. Remember also that creosote and other solvents are poisonous to all life forms.

A more expensive form of preservative but one which can be painted over is the organic solvent—a preservative chemical which has been dissolved in white spirit or petroleum oil. Organic solvents can even be used to treat wood which has already been attacked by fungus or insects.

Whenever a post or piece of fence is being replaced, the new section must be treated with a preservative, or it will quickly rot.

Paint acts as an effective barrier for wood only if a new coat is applied immediately the old one shows signs of flaking or blistering.

Remember when using wood pre- servatives to wear protective clothing and eye protection. Always apply the preservative in the open air or at least in a well ventilated room.

Repairing a post

The most likely place for a fence post to become damaged is at, or below, ground level. At this point, the wood is almost permanently damp, causing it to rot. Once a post is rotten, it can give no support and the section of fence butting up to it tends to lean out of alignment.

To repair the post you must cut off the affected part and attach a supporting spur. This involves temporarily supporting the fence and then digging a hole around the post about 600mm square and 300mm deep. Saw off the rotten part of the post once it is completely exposed and bolt on the concrete spur—150mm or 200mm coach bolts are suitable.

The straight face of the spur should be against the post. When it is in position, use a spirit level to check it is upright. Hardcore should then be packed around the bottom of the spur and the hole filled with a 1:3 cement and coarse sandmix. In Canada, set the cement below the frost line.

This method of repairing a post will withstand fairly severe weather conditions. Another method for a fence post which is not exposed to strong winds is the use of a metal spike.

After the rotten part of the post has been cut off, the ground must be tightly packed back into place. The metal spike is then driven hard into the ground, while gently holding the fence out of the way. Then bolt the spike to the post.

Repairing an arris rail

An arris rail—the horizontal bar of a fence—can be repaired temporarily if broken at the tenon or in the shaft by using a metal bracket to bridge the broken part.

If the tenon is broken, first level it off and then soak it with a preservative. Using galvanized or sheradized screws, fix the arms of the bracket to the post in the same place as the rail was originally fixed. With the bracket in place, screw both sides of it to the shaft of the arris rail.

When using a metal bracket to repair the shaft of an arris rail, screw it to one side and then with the aid of an assistant push the other side inwards and screw the bracket to that.

It is most important to use galvanized or sheradized screws in external woodwork. Ordinary screws will simp- ly rust away—causing unsightly stains —or fuse with, and split, the wood.

Fitting a new arris rail

When ordering a new arris rail, measure the distance between the two upright posts and add at least 75mm for the tenons. You may need to whittle away at the rail so that it fits into the mortise in the post. Treat tenons and mortises with preservative.

If you cannot force the posts far enough out of line to enable you to spring the ends of the rail into the post, you will have to use metal brackets or wooden chocks.

For the latter you need four 25mm x 20mm offcuts of wood to fit around the mortise. They must all be coated with preservative and then all but the top piece screwed into position. With this done, the rail can be slotted into place and the fourth strip of wood screwed tightly down for a firm grip around the tenon. Do this at both ends of the rail.

New boards in feather fencing

A feather fence is one which is made up of slightly overlapping vertical strips of wood. It is a simple matter to replace either one single board or to erect a whole series to form a complete new section.

When only one board needs replacing, remove the nails which are securing it and make sure that those securing the boards on either side of the damaged board are well banged in. Then slide the thin edge of the new board under the thick edge of the old one and nail through the overlapping edges with galvanized nails.

If a whole series of boards needs to be fitted, follow exactly the same procedure except for using a spirit level every fourth board to check that they are vertically level.

Gravel boards

As all wooden fences are at their most vulnerable where they touch the ground, a gravel board is usually fitted to minimize the risk of damp rising through the fence.

Most gravel boards are made of 150mm x 50mm hardwood. Alternatively, the fence can either be set on a single course of bricks topped with a strip of roofing felt, or on a custom-designed concrete panel.

To fit a wooden gravel board, clear away any soil or debris from around the base of the fence to form a recess for the board. Treat the board with preservative and either fit it into pre-cut mortises in the wooden posts or nail it through wooden blocks attached to the inside of the post. The blocks can be of the same wood and need to be set back from the edge of the post so that the gravel board will be flush with it.

If the posts are concrete, drive pegs into the ground butted right up to the post. The pegs should be made from treated 50mm X 50mm hardwood and at least 600mm long. Leave about 150mm protruding from the ground and— after measuring and cutting the board so that it fits tightly between the posts —nail it to the pegs.

Concrete gravel boards are also available, designed for use with concrete posts. Such posts have a groove on the inside surfaces, into which the concrete gravel can be slotted. Fencing panels are ideal for use with this system because they too can then simply be slid into position.

Panelled fencing

Interwoven panelled fencing is the simplest type of fencing to erect but it has the drawback that even the slightest damage to a panel usually means that the whole section has to be replaced. Being very light and often tall, woven panels are especially susceptible to damage from strong winds. Since it is an expensive business to replace entire panels, such fencing should always be set on a gravel board. The slats which make up woven fences are very difficult to obtain individually—unless a second-hand panel is available from which slats could be taken. It is usually always necessary to buy an entire panel. They are sold in standard sizes.

Panels can be cut to size, if necessary. To do this, hold the panel in the correct position and mark off the overlap. Carefully remove the end battens with a claw hammer. These will be longer than the middle battens because they extend up level with the top rail. They should be re-nailed inside the marked lines and underneath the top rail so that the excess protrudes from the bottom. It can be sawn off when the batten is in position. The surplus part of the panel can also then be sawn off, using the end batten as a guide. With this done the panel is ready to be positioned alongside another and hammered into its correct place.

Do not forget that panel fences, like other wooden types, must be regularly treated with preservative if they are to stay in good condition.

Removing a wooden post

It is sometimes very difficult to remove an old wooden post which has been set into concrete. However, the job can be made easier by using a strong rope-leverage system.

First, temporarily support the fence by tacking a sturdy batten to the top arris rail on either side of the post. In the case of a slatted fence, remove one board from either side of the post. Afterwards, dig out as much soil as possible to completely expose the base of the post in its bed of mortar.

Hammer in a 100mm nail about 300mm from the ground on either side of the post then tie a strong rope round the post immediately below the nails, leaving enough of the rope to tie around a suitable levering post. The levering post must be of very sturdy wood. Two nails should be hammered into, it about 30mm from the end to provide a grip for the rope.

Stack some bricks under the levering post about 100mm higher than the nails in the post. Push hard on the stick to ease out the post, adjusting the height of the bricks as necessary for maximum leverage.

The new post should already be pre-treated. Insert it in a hole at least 600mm deep and after packing in some hardcore, fill in the hole with a 1:3 cement and coarse sand mix. The top of the new post should either be cut slanted at an angle of 30° and painted with creosote or have a hardwood or metal cap screwed on to it. Either of these methods helps prevent penetrating damp by protecting the exposed end-grain of the wood.

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