Why Outdoor Wood Wears Out

Wood outside the house works hard. Shutters, front doors and pergolasPergolaAn open shade structure in a garden, on a terrace or a roof, made of posts and beams with slats, reeds, fabric or plants on top. It is often made of wood. take the sun all summer and the rain all winter, and wood reacts to both. Once you understand what wears it down, you understand what it needs to last.

The sun

The sun attacks the finish first. VarnishVarnishA clear or semi-transparent finish for wood that lets the grain show through and protects it from sun, rain and wear. fades and thins, while paint loses its sheen, hardens and opens fine cracksCrackA split or gap in render, concrete, a wall, a coating or wood. Fine cracks are usually only on the surface; ones that grow, keep reopening or run diagonally need attention.. Once the wood is left bare, its surface changes: it starts greyingWeathered (grey) woodThe grey, rough layer wood develops when it is left unprotected in sun and rain. It is surface wear and usually comes off with sanding., the fibres loosen and the wood feels rough to the touch.

On one pair of shutters, the sun had stripped the colour from the wood completely. It had turned grey and split along the grain across the panels.

Water

Wood soaks up water and swells, then shrinks again as it dries. That movement, over and over, breaks the paint, and more water gets in through the cracks. Water stays where it can't run off: at the bottom of each leaf, in the joints, where thin battens cross, and where wood rests on marble or a floor. There, over time, the wood can rotWood rotDecay of wood caused by fungi when it stays damp for a long time. Rotten wood goes soft, gives when pressed or crumbles, and can't be saved with paint..

On one set of old shutters the paint had peeledPeeling paintWhen paint loses its grip and lifts off in flakes or sheets. It is almost always a sign of a problem underneath, usually damp or poor preparation. everywhere, but the worst damage was at the bottom ends of the leaves.

What to look for

• Paint that peels or blisters, with bare wood underneath.
• Wood that has gone grey or feels rough.
• Cracks running along the grain.
• Joints that have opened up, or leaves that no longer close properly.
• Soft spots. Press a screwdriver into the bottom ends and the joints. If the wood gives or crumbles, it has rotted.

Most of these are surface wear and can be put right with sandingSandingSmoothing a surface with sandpaper or a power sander to remove bumps, loose old paint or gloss, so the new paint or varnish grips well and comes out smooth. and a new finish. Rotten wood, though, can't be saved with a coat of paint: that piece needs repairing or replacing. How far the damage goes only shows when someone looks at it up close, and often only fully once the old paint is off.