©2005 mark laurence
design note no. 3074
subject: |
Terracing a slope with decks |
problem: |
Traditional terracing methods are extremely expensive. |
The traditional way of terracing a slope can become a major civil engineering job. Terracing with decks and timber provides an alternative.
A small garden with a slope of about 1 metre. In a small space, this is a significant amount.
You can see from the planting bed, just how much the site drops.
These raised beds (newly planted in pic) are built into an existing back, along with a recessed seating area.
We have established in design note 2073: changes of level that terracing is the best - indeed perhaps the only - way to deal with slopes, especially steep ones. Multi-level decking is one way of dealing with this.
problem:
The use of stone, block or brick to build walling, whilst giving the greatest sense of perminance and durability, can be a massively expensive building project.
solution:
Timber decks can be built on posts set into the existing slope without the need to excavate massive amounts of soil. In most cases, some excavation will still be needed but combined with timber retaining walls and steps, this becomes a much more cost-effective method of construction.
Cost is not the only benefit as timber is a warm, natural material to use and has a character and charm all of its own. Without in any way being flimsy, wood has a lightness about it that is exciting. Standing on a deck that looks out over a drop in height is a bit like standing on the deck of a ship, or in a treehouse. You can just let your imagination go.
Timber is also an environmentally benign material, so-called carbon neutral because it is a renewable resource. Tropical timbers are strong, durable and beautiful but should be researched to ascertain their origin. Only accept them if they display the FSC mark. Even then, a locally sourced timber might be better - native oak, for example. Don't enhance your own environment at the expense of another.
The durability of a timber is also affected by how you treat it. Many conventional preservative treatments contain toxins that are carcenogenic. Avoiding contact of timber and earth is perhaps the single biggest factor in preventing decay, although this is not always possible.
This drawing shows how you might use multi-level decks to avoid using cut-and-fill terracing techniques. Of course, this is much simplified and there would have to be steps and perhaps timber walling to create raised planters
summary:
- Where a slope or drop has to be dealt with, use decking on multi levels
- Combine decking with timber steps, and walling to create level planters
- Take advantage of the unique qualities of wood to create areas of beauty
- Take note of lines of movement and still-points in your layout
- Be aware of the environmental impact of your timber choice
You may wish to look at the construction notes section, which deals with methods of building retaining walls, beds and decking.