Powder coated RSJ’s for retaining wall

[Dan1983]

Afternoon all,

Has anyone here used powder coated RSJ’s for a retaining wall?

Looking to see if the powder coated route will be better than painted longer term?

Reservation is any damage to powder coat will be hard to touch up/ stop flaking etc longer term

Cost wise powder does not appear to be a great deal more 

[nod]

Hot dipped is better Probably cheaper also 

[Onoff]

Powder coat cracks, water gets in. 

 

Galvanise and paint in black bitumen I would. 

 

Galvanise and powder coat if you must but no way would I powder coat over plain steel. 

 

Is it that you're wanting a particular colour?

[Dan1983]

Nothing special just matt black ideally.

Just the place that can supply the powder coated RSJ’s are saying the powder coat finish will last a very long time which I’m unsure on

Sure the football club house we were at today had powder coated beams and surface type rust was coming through which made me think if powder coating is the best way to go in a garden 

[JohnMo]

Had plenty of stuff powder coated in the past, great for car wheels, but not had much luck with other things.

 

Hot dip galvanised will last a life time.

 

Your other issue will be the words retaining wall - meaning it's structural. Unfortunately defects in steel cannot be seen when powder coated. Any defects in the coating created a galvanic corrosion cell and the base material disappears very quickly. All hidden by a thin plastic layer.

 

  On 01/02/2025 at 19:37, Onoff said:

Galvanise and paint in black bitumen I would.

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Either that or just plain hot dip galvanized. If it's on show and you want a colour, etch prime and top coat, after galvanising.

[Dan1983]

Retaining wall wise it should be fairly light work around 3 sleepers high

Painting was my other option was just trying to get away from having to repaint every couple of years but maybe pay off in the long run by the sounds of it!

[JohnMo]

  On 01/02/2025 at 20:46, Dan1983 said:

fairly light work around 3 sleepers high

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Why do you need steel, at all?

[Dan1983]

It’s mainly for the asthetics John to be honest

The tallest part approx 11m wide may end 4-5 high worst case

Also longer term will make replacing sleepers easier if ever required but going oak so hopefully won’t need to 

Edited February 1 by Dan1983

[JohnMo]

  On 01/02/2025 at 20:50, Dan1983 said:

Also longer term will make replacing sleepers easier if ever required but going oak

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You really need to look at the compatibility of oak with metals, especially when wet. Oak can be pretty acidic and will eat carbon steel and low grade stainless, in a dry space you can get away with hot dip galvanized, but in a wet environment the steel work could fail well before the wood does.

 

We did a sleeper retainer wall on our last house, and used vertical sleepers to attach the horizontal one too. 10 years later they all looked as good as new.

 

Our current retaining wall was a little different and a lot bigger - no screws used or metal framing. They are concreted in place.

 

 

 

 

[Roger440]

I wouldnt consider powder coating steel in this application. Its doomed to early failure.

[Onoff]

Someone on another forum asked a similar question. I said black bitumastic paint and they were happy:

 

[Dan1983]

Thanks all

Only issue id be concerned with on bitumen paint is it going soft/ tacky in hot weather?

Also can a decent finish be achieved?

[Roger440]

To be honest, the life time of the steel is the least of the problems. The sleepers will rot out long before the steel either way.

 

Unless you are using real, second hand hardwood railway sleepers.

[kandgmitchell]

We used 127mm x 76 UB's and dropped the sleepers into the flanges. Painted the steels in Everbuilds Black Jack bitumastic paint first. Doesn't get sticky in the sun and I would expect the steels to last a very long time and it'll be my children replacing the treated sleepers I reckon.

[Dan1983]

Many thanks all

Think my decision will be hot dip galvanised then paint as above