TV

Netflix has the TV show Massive Engineering Mistakes. (Spoiler; bridges feature a lot). Another recurring theme is the designer’s insistence on the use of a particular material often where no knowledge, providence or experience of the performance of that material in a new environment and climate. There are plenty of lessons to learn for application in landscapes and gardens. The biggest being that because something has been shown to perform in one location don’t assume it will therefore be universally suitable. Consider the risks and test.

Oak

Oak doesn’t seem to have the reputation it once had. Several contractors and timber research bodies have reported failure of oak when used as posts sunk into the ground. The providence of this oak and the ground conditions have not been declared but an argument has been made for oak to employ the use classification system given to other timbers ie UC4 = suitable for use in contact with ground/ ground water.

I would always list the specification of any timber in the written doucument or on the drawing:

UC4

DC2 (durability class)

SC: D40 (strength class)

Appearance grade: QP-1

Section 150x150mm

Etc

 

Powder coated steel

To treat steel against degradation we can powder coat it. On its own powder coating will not adhere with any durability to steel and therefore steel is often pretreated with a range of chemical baths and sometimes mechanical finishes to ensure good adhesion.  Zinc coating is probably the best substrate to use under a paint finish. Even if the paint starts to lift, the steel remains protected and can be repainted if necessary. A more robust solution is to use stainless steel (grade 316) rather than coated steel. Treatment will be required to reduce the surface polish and improve paint adhesion.

Not all powder coating will remain durable when immersed in water. Specific marine grade products should be used, and an experienced paint applicator should be used.

Powder coating colours,like many paint systems, are not entirely UV resistant. Dark colours are likely to have a noticeable bleached effect after only a few years.

 

Need to know about a technical topic?

THE Society Garden & Landscape Designers have a series of short (1hr) talks on a range of very specific subjects. Visit their events page to see the latest listings. These are just £5 for members and £10 for non-members. If you can’t get a place they will be repeated.

I am giving the following talks:

9/4: Soakaways

23/4; Equal thresholds

21/5: How to specify timber

4/6: Ground anchors and ground screws

18/6: Ratios for steps and ramps

16/7: Unit and material dimensioning

 

Principles of design

I am privileged to be the course leader for London College Garden Design’s Construction Design Course. We talk a lot about what the driving philosophy might be for a project or detail, what framework will help steer decisions. I have a background in Industrial design, and I return time and again to the principles postulated by Diter Rams, head of Braun design. They are universal and still remarkably relevant. Read a profile his genius here