Guide to Preparing Interior and Exterior Timber

Guide to Preparing Interior and Exterior Timber

Whatever your joinery project: Plan, Prepare, Prime then Paint. 

For best results when approaching any interior or exterior joinery, follow this guideline in conjunction with any coating specification. 


Timber Selection

Prior to beginning any joinery project, consideration should always be given to the choice and use of a timber species. It is important to consider which timber species’ natural durability is sufficient for its intended use.

Where timbers which are not durable are used, such as softwoods and hardwoods in Durability Classes 4 or 5 (reference BS EN350-2:1994), preservative treatment will be necessary for exterior use.


Ensure surfaces are clean and dry condition and free from; dust, dirt, wax, grease and surface moisture. The moisture content of exterior should not exceed 18% and 14% for interior timber.

Timber surfaces should not be over-prepared with fine abrasives, as this will reduce the degree of absorption. Wire wool and metallic brushes must not be used.

Failure to provide an adequately prepared surface will result in a poor adhesive performance of the coating system.  


On all joinery projects, ensure to use fillers specifically designed for use with timber. General or all-purpose fillers are not suitable, particularly on external areas, where even wood fillers cannot cope with timber movement and work loose. 

When using translucent coatings, there is little need to fill fascia board joints and butt joints as the change in grain from one section to the other may draw attention to the filler. Where possible when coating with a translucent coating, filling and stopping should be avoided in order to avoid obscuring the grain.


Where applicable, all brush coatings should be applied with a good quality brush. Water-borne coatings should be applied with a synthetic bristle brush.

All coatings should be laid off in the direction of the grain, with the minimum number of brush strokes required to give an even finish.

Weather Condition

Do not apply coatings where there is a risk of rain or frost. In general, solvent-borne coatings should not be applied below 5˚C, and water-borne coatings should not be applied below 8˚C. Always refer to data sheets for more detailed information.

Personal  Protection

Treatments for the removal of surface coatings (such as sanding, burning off, use of chemicals) may generate hazardous dust and/or fumes. 
Always work in well ventilated areas. 

Use suitable personal protective equipment including respiratory, eye and skin, as necessary. Manufacturer’s advice should be followed at all times.


Prior to applying a coating, particular attention should be paid to ensure end grain is thoroughly treated to saturation. Apply first coat ‘wet on wet’ until no more product is absorbed.

When applying coatings, in order to ensure optimum protection and durability, it is essential to achieve the required coverage rate.

The final overall appearance of the finish is dependent on a number of factors, including colour, absorbancy, and texture of the timber, as well as the shade and type of coating used. We therefore strongly recommend that a trial application is undertaken before work is carried out to confirm its acceptability.


For the application of products, always apply in accordance with the relevant Technical Data Sheets. In addition, all products should be used in accordance with BS 6150:1991 Code of Practice for Painting Buildings and BS 8000:Part 12:1989 Workmanship on Building Sites.


For further information on any of products, coatings or applications please feel welcome to give us a call here at HSP Joinery on 01793 511537. 

We will endeavour to work closely with you for the entirety of your project to ensure that you get the best coating for your project.

Because beautiful wood deserves a beautiful finish.

Professional Protection for Every Joinery Project. 

Posted on 02/12/2016 Home, HSP Joinery 0 846

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