Timber treatment is a critical part of wood preservation, especially for outdoor projects exposed to moisture, insects, and weather. Two common methods for treating timber—pressure-treated and dip-treated—help extend wood's lifespan by adding protective chemicals that resist decay, fungal attacks, and insect damage. However, each method has unique attributes, advantages, and disadvantages, which can significantly impact the wood's durability, maintenance needs, and suitability for various projects.
What Is pressure-treated timber?
Pressure-treated timber undergoes a process where wood preservatives are injected deep into the wood fibres. The process begins by placing the timber into a vacuum chamber that removes the air within the wood cells. Then, under high pressure, preservatives are forced into the wood, allowing them to penetrate deeply and providing long-lasting protection against rot, decay, and insect infestation. This type of timber is often recognisable by its greenish hue, a result of copper-based preservatives.
Advantages of pressure-treated timber
Enhanced durability - pressure-treated timber is highly durable and well-suited for structures exposed to extreme weather conditions or high moisture levels, such as fencing, decking, and outdoor furniture.
Low maintenance - due to the deep penetration of preservatives, pressure-treated timber requires less frequent maintenance than dip-treated timber, making it ideal for long-term projects.
Extended lifespan - this timber has a considerably longer lifespan, often lasting 15 to 40 years, depending on the type of wood and treatment.
Disadvantages of pressure-treated timber
Higher cost - the treatment process is intensive, which makes pressure-treated timber more expensive than dip-treated timber.
Chemical content - although effective, the chemicals used can raise environmental and safety concerns, especially if the timber is burned.
Weight and density - pressure-treated timber is denser, making it heavier and sometimes harder to handle than untreated or dip-treated wood.
What is dip-treated timber?
Dip-treated timber involves immersing the wood in a tank filled with preservative chemicals. The timber is dipped or "soaked" for a short time, allowing the preservative to coat the wood’s surface. Unlike pressure-treated wood, this treatment method does not penetrate deeply; the protective coating mainly remains on the outer layers, offering some level of protection but not as deep or long-lasting as pressure treatment.
Advantages of dip-treated timber
Lower cost - dip-treated timber is usually more affordable, as the process is quicker and requires less-intensive equipment than pressure treatment.
Aesthetic appeal - the lighter coating of preservatives gives dip-treated wood a more natural appearance, which many people find appealing, especially for decorative outdoor structures.
Ease of handling - since dip-treated wood is not as dense, it is generally lighter and easier to work with, making it more user-friendly for small DIY projects.
Disadvantages of dip-treated timber
Shorter lifespan - the surface-level treatment means the protection doesn’t last as long as pressure-treated timber. Dip-treated timber may need retreatment every couple of years to maintain effectiveness.
Higher maintenance - due to its limited preservative penetration, dip-treated wood requires more frequent reapplication of protective coatings, especially if exposed to constant weathering.
Limited durability - while dip-treated timber is adequate for low-exposure areas, it is not suitable for heavy-duty applications or locations exposed to moisture or harsh elements.
Choosing between pressure-treated and dip-treated timber
Your choice between pressure-treated and dip-treated timber depends on factors such as the location of your project, budget, and maintenance preferences.
For heavy-duty applications like decks, structural supports, or areas that will face constant moisture, both pressure-treated timber and dip-treated timber will have greater durability and a prolonged lifespan with the correct application of wood treatments or protective coatings.
Timber products from Witham Timber
With over 240 years’ experience in the supply of quality garden timber and landscaping products, we specialise in wooden fencing supplies, garden decking, sleepers, and garden structures including timber sheds, gazebos and pergolas, stocking pressure-treated and dip-treated products. For help with any of your timber requirements please email the sales team at sales@withamtimber.co.uk or give us a call on 01205 359188