Water-based Paint On Exterior Timber

August 7th, 2018

Timber products that face the outside world, i.e. windows and external doors, suffer the worst that the environment can offer. They have to be resilient to changes in temperature, weather conditions and infection. As such, it is very important to consider what products you use as an outer cover for your timber.

Externally exposed wooden window frames that are not protected with a finishing coat will weather badly inducing the timber’s colour to fade, causing aesthetic damage, though the problems aren’t just skin deep. Timber that isn’t treated to face outdoors conditions is susceptible to damage from mildew and UV light amongst other things.

There are four main options to choose from when considering what product to treat your wooden window frames with. They are preservatives, paints, varnishes and exterior wood stain. Depending on the product and the desired effect all these products have their pros and cons, though we strongly advocate the use of water-based paints in the final finish.

Most oil-based paints and preservatives that you buy will be high in volatile organic compounds (VOCs), which are employed to keep the paint in a stable state whilst not in use. These VOCs generally evaporate at room temperature giving off a strong smell as it leaves the paint to dry. When airborne they can accelerate the rate at which nitrogen oxides in the atmosphere react with UV rays, catalysing the creation of photochemical smog and low-level ozone. Unlike many other outdoor coatings, water-based paints are virtually VOC free, thus minimising the effect of the industry upon the environment.

In addition to its environmental impact, water-based paint is also more beneficial to the timber you are covering. With varying humidity naturally occurring within a wood, timber often expands and contracts day to day. Oil-based paints are less malleable and so don’t react too well to this movement.

Water-based varieties instead move more freely and also allow the surface beneath to ‘breath’ more easily, preventing water retention that can harbour mildew which will cause the timber to rot from within. This is extremely beneficial in harsh weather conditions and will ensure a lengthier protection on your timber window frames. Importantly, however, you must remember not to paint over oil finishes with a water-based alternative, because as the coat below expands and contracts, it will crack and blister under the new coat, rendering it useless.

Some may argue that you cannot get the same finish with a water-based paint as you can with oil, however as regulations have been tightened on the use of VOCs in the industry, a lot more time and money has gone into developing water-based alternatives which will provide the same required finishes as their more harmful predecessors.

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