Decking in a Damp Merthyr Tydfil Garden

A deck gives you a flat, dry-footed place to sit without digging out half a hillside, which is why so many people on steep ground in Merthyr Tydfil ask us about one. The worry we hear most is the weather. The town sits high at the head of the Taff valley, close to the Beacons, and it gets a lot of rain. Will a timber deck just turn green and rot?

It can, if it is built badly. Built properly, a deck copes well. This guide sets out what makes the difference in a damp Merthyr Tydfil garden. For the full range of what we build, see our garden decking page.

Why damp decks fail

Timber does not mind getting wet. It minds staying wet. Most of the rotten, slimy decks we are asked to replace went wrong for the same few reasons:

• Joists sitting directly on soil or on a solid slab where water collects.
• No airflow under the frame, so it never dries after rain.
• Boards laid flat and tight, so water and leaves sit in the gaps.
• A position in permanent shade, often tucked against the back of a terrace.
• Weeds growing up through the frame and holding moisture against the timber.

Each of those is avoidable at the planning stage, and that is where we spend our time.

Keeping the frame off the wet ground

The frame is the part you never see and the part that matters most. We set posts or pads on firm footings, keep timber clear of the soil, lay a weed membrane with gravel beneath, and leave space around the sides so air can move through. The joists are pressure treated, and any cut ends are sealed with preservative too.

In Merthyr Tydfil it is also worth asking where water from the rest of the garden goes. A deck built at the bottom of a slope can end up sitting over a stream every time it pours. If that is happening, we deal with the run-off first; garden drainage solutions in Merthyr Tydfil explains the options.

Boards that stay grippy

Two things make decking slippery: algae and a smooth surface. In a wet town you want to fight both. Grooved timber boards help, anti-slip boards with gritted inserts help more, and many composite boards are made with a textured finish that copes with damp well.

For a shaded Merthyr Tydfil garden that rarely sees the sun, we will often suggest composite. It costs more at the start but does not need staining, and it does not go green in quite the same way. Our guide to composite or timber decking weighs up the two, and how to stop decking going slippery covers upkeep.

Using a deck to tame a slope

This is where decking earns its place in Merthyr Tydfil. Many gardens behind the old terraces climb steeply from the back door, and newer houses on the valley sides can have a drop just past the patio. A raised deck on a timber frame gives you a level platform without the digging and walling that a terrace needs.

Higher decks need sturdy framing, proper steps and a balustrade, and anything raised above the ground should be planned with privacy and neighbours in mind. It is sensible to check with the council before building a raised platform. Raised decking: frames, steps and balustrades goes through the detail.

Where the slope is very steep, a combination often works best: a deck near the house and a terraced garden held by walls or sleepers further up.

Picking the right spot

Position makes a big difference to how quickly a deck dries. If you have a choice, put it where it gets sun for part of the day and some breeze. The spot right against the house is not always the sunniest; in a Merthyr Tydfil garden that faces up the hill, the top of the garden may catch the light for longer and give you a view down the valley.

Think about the wind as well. An exposed deck is a pleasant place on a still evening and a cold one in a westerly. A screen, a pergola or a fence on the windward side can help. Our article on strong fencing for windy Merthyr Tydfil gardens is useful here.

Small yards and awkward access

Not every Merthyr Tydfil deck is a big raised platform. Many of the older terraces have a small yard behind the house with a step or two up to a garden that climbs away beyond. A low deck across the yard can hide cracked concrete, even out a couple of changes in level and give you room for a table and chairs.

Access shapes these jobs. If there is no rear lane, every board, joist and bag of gravel comes through the house, so we plan deliveries carefully, protect floors and cut to size outside where we can. Long boards are sometimes the deciding factor, and we may suggest a board length or layout that makes the carry manageable without spoiling the finish.

If your yard is full of old sheds, rubble or overgrowth, it will need clearing before any frame goes in. We can do that as part of the same job; see garden clearance in Merthyr Tydfil.

Looking after a deck through the winter

A little care goes a long way in a wet climate:

• Sweep leaves off in autumn and keep the gaps between boards clear.
• Wash the surface down in spring to shift algae before it takes hold.
• Re-treat timber boards when water stops beading on the surface.
• Keep pots on feet so they do not trap water against the boards.
• Check the frame and fixings once a year, especially near steps.

With that routine, a well-built deck will give you many years of use. How long should garden decking last? gives a realistic idea.

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