Furring channel plus decking boards to dress up stairs

[adro]

Hi Team,
I have some old red brick front steps that were previously cladded over with a timber frame build out and merbau decking boards, built by the previous owner (property flipper).

They did a terrible job and these ended up rotting away. I am keen to re-do it but want to get it right. It seems they built the frame directly onto the brick, leaving no space or ability for water to drain out and it is fully exposed to the elements.

I was thinking to use a slim metal framing system this time around, and possibly composite decking instead of natural timber - but not sold on this just yet.

Two questions for now:

1. Is there a slim line metal system I could use? I was thinking about galv furring channels but not sure on their longevity. I would probably still put a rubber joist cover on them, but they would potentially be sitting in moisture.

2. Any idea on longevity of composite decking in full elements? I have had some composite garden edging crack under similar conditions in about 3 years.

[MitchellMc]

Welcome to the Bunnings Workshop community @adro. It's wonderful to have you join us and many thanks for your question about cladding with decking.

I'm sure there are quite a few slimline metal furring channels that could be used. I'm not aware of us selling any systems, as although they will raise the timber off the brick, they are still not providing adequate ventilation to the decking boards. 

Composite decking is perfectly fine in full elements and, by all reports, could possibly outlast timber decking, especially if it is not regularly maintained. However, products like Ekodeck still must be installed with a minimum clearance. For Ekodeck it is 90mm as any less and excessive heat is built up. The boards require ventilation under them.

What sort of clearance are you talking?

Mitchell

[adro]

@MitchellMc 
Thanks for the response and sorry for delay in reply. Appreciate the advice about ventilation and this is definitely what I am hoping to achieve while avoiding the water trapping mistakes of the past build.

Providing a bit more context and my current working solutions below.

I have attached a photo (first image below) of the previous frame that was built by the flippers. I am looking to avoid the mistakes as this was the result after only 3.5 years. If I am to do this again, I would hope for much longer than that in longevity. I think the mistakes they made (but please confirm/add others) are:
1. They have bolted the boards direct to the vertical riser face enabling water to be trapped

2. Where they didn't need to elevate the frame, they bolted direct to the horizontal tread

3. They didn't apply any kind of joist protection strips

4. Appears it was only H2 treated and not H3, judging by the colour(?), but I could be wrong about that. I assume H3 would have been more resilient to the drainage flaws/lack of joist protection strips?

Other issues I am grappling with:

1. The top step (before the landing) does not have a recess under the nosing, but all other steps have the brick overhanging by 20-25mm

2. The riser dimensions vary. Top riser (to landing) is only 103mm, the next three down are about 165mm +/- 5mm, and the last to the garden path is 200mm.

3. The grey post at the landing (refer second image) is not aligned to the stairs so there is a lateral gap to be closed up of about 150mm (thinking of putting in a hand rail here to make this less obvious - honestly don't know why they put the post where they did)

4. How to enable good ventilation when I also want to cover up the sides of the brick stair case with deck cladding? Does a 5mm gap between boards provide sufficient space to enable air movement? This would be same as previous design and that didn't overcome the other issues (ie lack of spaces to brick).

My current solutions:

1. Rebuild similar frame with H3 - and allow at least 5mm gap (using spaces/shims - is that enough drainage clearance?) to any brick work and use a PVC joist strip to cover all horizontal elements of the frame (see Sketchup design images below). Materials include:

• 70x45mm H3 framing throughout which allows for the space below each frame box to the underlying brick tread
• 90x19mm merbau decking for treads
• 140mm merbau decking for risers (single board seems to be working out better than trying to run 90mm boards behind each tread, or cutting them down)
• Still need to figure out how I am going to support the frames. The space beneath each frame is about 25mm at most, some as little as 15mm. The only exception is the bottom stair frame which drops about 65mm to the concrete path.

OR

2. Forego the framework but using some kind of galvanised steel furring channel system instead to allow drainage of water under decking boards and eliminate the chance the framing will rot

Old framingGap from stairs to porch balustrade post

[MitchellMc]

I'd have to agree with your suspicions that it's actually H2 termite resistant timber not suitable for exterior use. They were my thoughts as soon as I saw that blueish treatment. By replacing it with H3, you'll see a significant lifespan increase. You might like to also spray your frame timber with TWA Woodcare 300g Ecoseal Tanalised Timber Treatment or paint it with Bondall 1L Inground Timber Protector, which should bring the H3 treatment closer to H4, which is suitable for inground use and semi-permanent water contact.

I'd follow a similar connection process to the one they've used. Dynabolt into the step's riser and use angle brackets to Dynabolt the frames into the stair treads. The frames can be supported and raised on plastic shims.

Mitchell

[adro]

Thanks for the feedback and suggestions @MitchellMc 
Your confirmation of H2 now gives me concern for the main deck in the backyard 

I had already ripped up a part of it built over a concrete slab (fully exposed and rotted away in same timeframe, frame also built directly onto the slab with no spacing).

The rest of the deck is probably built with the same stuff, and although its mostly covered, the edges are obviously always getting rained on etc - at least it sits off the ground with much better ventilation.

I am planning to replace some of the nails with screws this week as some of the boards are starting to lift - probably suggests the timber below is losing integrity so may end up with a bigger job of replacing joists/bearers with H3.... 

Real buyer beware experience unfortunately - too many cowboys skimping on what amounts to a few hundred $ in materials which ends up costing the buyer thousands to fix.

[MitchellMc]

Geez, that's not good @adro. So, the decking boards are nailed down? That's a pity, as if they were screwed you could relatively easily pull all of them up, paint the timber with the products suggested above and relay the boards. That would at least give the frame some extra protection.

Keep us updated and reach out if we can be of assistance.

Mitchell

[adro]

@MitchellMc 

Yes they are except for about four rows up against the house. They are screwed presumably to allow for inspection of pests and access to some plumbing. I guess doing that didn't cost them extra?

Will take a look anyway and certainly give those products a go if it's not too late.