A single coat of Cuprinol or Sadolin clear wood preservative should be applied both internally and externally and allowed to penetrate and dry for three days before treating with weather protector products. The three day drying makes the use of these spirit based products suitable even when over-coated with water based stains such as Superdec.
For external treatments you can choose from many brands but we have found Sadolin or Sikkens to be excellent. Other recommended products are Jotun/Butinox or sikkens Novatech/Novatop.
Whichever product you choose it must satisfy four criteria.
It must be a weather protector rather than a paint
It must be a waterproofer (many preservatives do not have waterproofing abilities. This is also true of many varnishes)
It must have at least a small pigment of colour to provide a filter against the sun
It must be of high quality, for joinery applications, e.g. front doors, windows, conservatories etc.
There are many lower quality stains available for sheds, fences, garden furniture etc. that really do not provide the correct weather proofing needed for a log cabin and/or need maintenance annually. These are generally the lower priced products. In our experience “Cuprinol Garden Shades” or “Ducks Back” have not performed well in log cabin applications.
It is always best practice to apply the treatments by brush and ensure that each coat is worked deep into all joints particularly at corners and between logs. Do not brush too thin or apply over thick. Ensure all faces and edges of doors and windows are also weather protected.
For the internal treatment, assuming you do not expect dampness being created in the cabin and also that you wish to retain the light pine appearance, simply apply the one coat of Cuprinol/Sadolin clear preservative or similar all purpose preservative.
If there is likely to be moisture created within the cabin e.g. from cooking, many people breathing, gas heater, open garage doors and concrete floors, hot tubs etc. then the internal faces of the walls and ceiling must also be waterproofed. You could use Sadolin Extra Durable Clear Coat or Clear Polyeurethane floor varnish. In all cases it is a good precaution to treat inside faces of doors and windows with the exterior weather protector stain to prevent differential moisture absorption that can cause warping of the doors or windows.
All treatments are to be applied in accordance with the product instructions and maintenance coats are to be applied at intervals recommended by the product supplier.
It is sometimes necessary to add a silicon sealant to some joints in the cabin. This is always needed for log end to end butt joints that occur in long walls and sometimes around door/window frames to wall joints depending on weather conditions imposed.
It is a simple case of running a bead of silicon water proof sealant into the joint to fill any gaps and provide a cover fillet.
However we recommend that the silicon is only applied after all other treatments are completed and the wood has dried and settled. For this reason our installers are not in a position to apply the final sealants and responsibility for doing this lies with the customer.