Log Cabin Timber Repairs

This case study has been compiled to show the repairs to a traditional log cabin that was suffering from water ingress.

Log Cabin

The log cabin has been constructed of round sections of pine laid horizontally. Over time as the timber has dried the timber leaving fissures that are running along the grain of the timber. The fissures vary in length, width, and depth and would not normally present a structural weakness.

In this instance, as the timbers form the exterior cladding it is essential that they provide protection against the weather and the elements so any cracks or gaps in joints present opportunities for moisture to penetrate the outer skin of the building.

Why is it important to protect against the moisture, apart from the obvious damp damaging the interior décor and presenting an unhealthy environment to live in?

Moisture can penetrate fine cracks in timber through capillary actions or if the crack is sufficiently large then driving rain and wind can push water in the property. Rising damp is moisture being absorbed by the substrate from the ground or standing water near the property. Rising damp can penetrate up to 3ft up a vertical surface.

An additional challenge with timber is that if the end grain of the timber element is not sealed then moisture can be absorbed if you think that when the tree was living then the water feeding the leaves would have made its way through the timber in exactly the same fashion. The image below showing the corner of the building shows where the end grain has been exposed.

End grain damage to timber

Wet rot needs a combination of warm temperatures, moisture and sugar for the reaction to take place. There is an abundant supply of sugars within the cellulose of the timber. So if the timber are not well ventilated allowing them to dry then the conditions can be created that lead to wet rot.

Wood-boring insects such as the common furniture beetle and the Wood Weevil are commonly attracted to wet rot as that is what they feed on.

Wet Rot

If we were to seal the timber without dealing with the wet rot, and wood-boring insects we would exacerbate the issue and further improve the conditions that promote wet rot and infestation.

In this case, we are using a two-pronged attack, the first is to immediately kill the wood-boring insects and rot that is present. The second is to provide longer-term term protection to areas that are at risk.

The Owner of the building used Rotafix Borotreat 10p. Rotafix Borotreat 10p is a boron-based wood preservative and timber treatment, designed to preserve wood from attack from dry rot, wet rot, deathwatch beetle, and the familiar woodworm or common furniture beetle so it is ideal in this application.

Rotafix Borotreat 10p comes supplied as a powder that is dissolved in water. The solution is then brush applied to the surfaces of the timber. Personal protective clothing is essential, and whilst the timbers are wet you are advised to avoid having pets and animals in the area.

Borotreat 10P

The second stage is to insert boron rods into the timber at the lower areas of the timber that are likely to be near standing water or where water might accumulate such as right-angle joints. The boron rods will dissolve with the moisture that is present over a period of 5 years, the boron from the rods will offer protection from rot and further infestation. We recommend that the rods are replaced every five years for continuous protection.

Boron Rods

After a period of 24hrs the Borotreat will have had the desired effect and we can turn our attention to sealing the property.

Some sections of the timber were beyond repair and need to be cut out to allow new sections of timber to be inserted.

OLYMPUS DIGITAL CAMERA

Rotafix recommended sealing the fissures with Rotafix RSA. RSA is a two-part epoxy adhesive specifically designed for bonding timber. RSA has the same coefficient of expansion as timber so as the timber expands and contracts as the temperature fluctuates the RSA and timber will not pull each other apart or force the fissure to open further.

RSA is also slow setting this allowed the Owner of the property to work diligently along the cracks filling and smoothing the surface. A special nozzle was supplied by Rotafix. The nozzle is formed from a copper tube that has been flattened. This nozzle attaches to the standard cartridge set supplied by Rotafix allowing the user to inject the RSA deep into the fissures completely filling all gaps.

RSA has the consistency of a thick gel like a soft vaseline or hair gel this allows it to be pumped onto surfaces where it will immediately grab and hold on a vertical surface.

The RSA is effectively in thick glue lines up to 20mm, but for aesthetics it is normal to bond a timber into large gaps to retain the appearance of timber.

Timber removed ready for new timber cladding

A piece of cladding such as that shown in the image below completes the repair.

Timber cladding to complete the repair

This image clearly shows where the RSA has been injected into the timber, sealing the fissure. A special flat nozzle was used to allow the RSA to penetrate deep into the timber. The joints between the timber elements have also been sealed with RSA.

Fissures filled with RSA

New sections of timber were created to fill the gaps in the areas where the damage was too extensive to repair.

Corner section of log cabin

The image below shows the section of the prepared timber inserted into the corner of the log cabin.

Corner repair to log cabin

The exterior of the building was coated with a Sikkens exterior timber product. The RSA will take the stain of the timber coating giving an invisible repair.

Timbers coated with protective sealant

All buildings benefit from ventilation, moisture generated by our breathing, showers and bathing, drying clothes needs to be given an opportunity to evaporate or escape or it will sit on cold surfaces and could lead to mould.

The final finish

For further information about timber repairs using Rotafix Structural Adhesive, Borontreat or Boron rods please contact Rotafix Technical Team to discuss your requirements.