Green Oak fixings into masonry

[SB1066]

Hello all,

I have recently built some outdoor green oak steps (although moisture reading says 12%), I’m in the process of fitting them. I have a support board against the wall which the stringers sit on. I am planning on attaching the board to the masonry via resin anchors and 10mm stainless steel threaded bar, then drilling a slightly larger hole in the oak, perhaps 12mm and using a 12mm washer to allow for movement. Does this sound appropriate? Tbh they are pretty much freestanding, but I have kids and there is a lightwell below so I’d rather have belt and braces.

Also would you recommend using a DPC membrane under behind the support board and on the bottom of the stringers in contact with the concrete pad?

Cheers

 

[Toby Newell]

Hello all,

I have recently built some outdoor green oak steps (although moisture reading says 12%), I’m in the process of fitting them. I have a support board against the wall which the stringers sit on. I am planning on attaching the board to the masonry via resin anchors and 10mm stainless steel threaded bar, then drilling a slightly larger hole in the oak, perhaps 12mm and using a 12mm washer to allow for movement. Does this sound appropriate? Tbh they are pretty much freestanding, but I have kids and there is a lightwell below so I’d rather have belt and braces.

Also would you recommend using a DPC membrane under behind the support board and on the bottom of the stringers in contact with the concrete pad?

Cheers

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Sounds good, that string looks amazing! And yes, put dpc between all masonry. BC would probably prefer 12mm bar, but 3 x 10mm bar should be fine. I use Blackjack flashing primer and bitumen flashing, raises the strings a mm or two.

Remember to protect before you fit the treads and risers. I apply a heavy coat of transparent preservative then use pure tung oil or an alkylalkoxysilane type cream. The tung oil looks nicer, but takes ten times longer, I apply 5 to 10 coats, oil might make the steps slightly slippery. The silane cream, which is basically industrial pledge, doesn't give such a deep colour but is a one coat affair. It also reduces the friction but is much lower build as it soaks in. The only downside to the silane cream is that you can never overcoat with another finish as nothing will stick.

Both will go a lovely silver grey over time, you just want to delay rot and cracking.

 

[SB1066]

Sounds good, that string looks amazing! And yes, put dpc between all masonry. BC would probably prefer 12mm bar, but 3 x 10mm bar should be fine. I use Blackjack flashing primer and bitumen flashing, raises the strings a mm or two.

Remember to protect before you fit the treads and risers. I apply a heavy coat of transparent preservative then use pure tung oil or an alkylalkoxysilane type cream. The tung oil looks nicer, but takes ten times longer, I apply 5 to 10 coats, oil might make the steps slightly slippery. The silane cream, which is basically industrial pledge, doesn't give such a deep colour but is a one coat affair. It also reduces the friction but is much lower build as it soaks in. The only downside to the silane cream is that you can never overcoat with another finish as nothing will stick.

Both will go a lovely silver grey over time, you just want to delay rot and cracking.

Hi Toby,

Thanks for the response and very useful tips! I was planning on using Danish oil as it seems to dry quicker than tung and I already have some in?!

I have 10mm threaded SS so I’ll use that with oversized washers to allow for movement. I think you’re right though 12mm would be better.

It feels like they’re taking forever - planing them all has been tedious to say the least

 

[Toby Newell]

Mmmmm, Danish oil is a generic term for a PU long (or spar) oil vanish, or wiping varnish as they say in the States. Basically a PU / yacht vanish with less PU and more oil, pretty much identical to the equally generic teak oil (whic may contain more tung oil for exterior use). Is pretty much a very poor performing finish. It has a medium build, so partially soaks in and is more flexible than normal PU varnish, but still leaves a thin(ner) skin that can crack and peel. Modern hardwax oils are very similar except without the PU and the addition of small amounts of wax. Your oil is probably mostly linseed, soybean and parrafin oil, it may contain some tung oil but this is expensive so you don't know how much! It might be high tung oil and great, or very low, unfortunately no one will tell you the percentage of tung oil (not even Liberon) Will give a lovely deep colour but pure Tung oil should last a lot longer. Liberon do a quick drying tung oil, which is 100% tung oil but with siccatives (and solvent) If you go for pure tung oil, or fast drying, you at least know you are getting 100% of the longest lasting a waterproof oil in your 'oil'!

Very rarely do you get a free lunch, faster drying = more siccatives = less penetration = more body (thicker film) = more chance of peeling. Modern 'oil' finishes are basically varnishes with slightly less siccatives and slightly more oil. They are marketing ruses. A true oil is basically simply 100% pure oil with or without solvent.

Boiled linseed oil with terebine driers and lead or zinc siccatives might of been sold as 'boiled linseed oil' but was effectively the first oil based varnish.

I apply 5 to 10 coats of pure tung oil, thinning the first one or two. For a cheaper job I use a siloxane cream. For maximum protection on doors, windows etc I use Sirca 2 part solvent polyurethane but this is incredibly difficult to apply for a non professional, also for stairs you want a low build finish that is easily repairable as they are likely to wear quickly.

 

[Toby Newell]

If you decide to use Danish oil, good luck, I see wrong application very, very often. It can be tempting to apply like a varnish but often this will never dry and go sticky. I would apply very thin coats and wipe off. Better to apply 6 thin coats than 3 thick coats. All oils take weeks or months to fully cure, in fact often some oil at the surface is partially uncured years later. It's important after you have initially wiped off to hang around for 45 mins, longer if in direct sun, the oil will often 'bleed' back or 'sweat' from the grain leaving little beads, you need to firmly wipe these off with a terry towel before they harden and go sticky. You need minimal sanding inbetween coats, I use a scotchbrite pad or old p240 or p320. You often hear you should use 0000 wire wool, but this is hilarious, unless you want to age the the oak with iron stains.

 

[SB1066]

If you decide to use Danish oil, good luck, I see wrong application very, very often. It can be tempting to apply like a varnish but often this will never dry and go sticky. I would apply very thin coats and wipe off. Better to apply 6 thin coats than 3 thick coats. All oils take weeks or months to fully cure, in fact often some oil at the surface is partially uncured years later. It's important after you have initially wiped off to hang around for 45 mins, longer if in direct sun, the oil will often 'bleed' back or 'sweat' from the grain leaving little beads, you need to firmly wipe these off with a terry towel before they harden and go sticky. You need minimal sanding inbetween coats, I use a scotchbrite pad or old p240 or p320. You often hear you should use 0000 wire wool, but this is hilarious, unless you want to age the the oak with iron stains.

Thank you - and you’re right, I didn’t spend all this time joining with traditional to spoil it with wire wool stains

 

[Toby Newell]

That looks fantastic! What beautiful wood. I would give the front of the treads a bit more of a sand, any planer or saw marks are areas that weather first.