Timber for outdoor use

Boarder1 · 01-08-2020 12:55pm #1

Hi,

The (unusual) outdoor balcony of my house needs to be replaced in part or perhaps in totality due to wet rot. The basic structure comprises two horizontal beams inserted into the masonry facade of the house and joined to a vertical post. The flooring is supported by joists inserted into the masonry facade. See photo attached. I'm in the process of purchasing timber. I gather that pressure treated deal (which I intend to cover with the requisite number of coats of wood preservative) will be adequate for this purpose. Is this correct? Also, can the use of wood preservative (I'm using Ronseal Woodstain) obviate the need to use pressure treated timber?

I'm a complete amateur in the area of woodcraft but intend to use tenon and mortise joints to join the horizontal beams to the vertical post I've installed mortise locks in the past so am not a stranger to chiselling! Forming the tenons will be the greater challenge. (Am I nuts to contemplate this?) I inquired at the (Rathdrum based and non amateur suffering) timber suppliers and I'd have to provide drawings if I wanted prefabricated machined timbers. I'm no draughtsman so this is outside my limited skill set.

Any insights would be gratefully appreciated.

Calahonda52 · 01-08-2020 6:28pm

Image is a bit dark to see underneath.

wood preservative and stain are usually two different products and stain on its own is not enough.

Is the vertical post just buried in the ground?

This will be the week spot as pressure treated timber does not do well when in wet grounds all the time
where is the wet rot.
have you access to a band saw for the tenons?

Piriz · 01-08-2020 6:40pm

you should use pressure treated timber for this job

if you need to replace the post there is pressure treated posts that can be put into the ground and there is other pressure treated timber that should not be put into the ground.

maybe there is galvanised steel brackets that would be better than tendon joints.

you also want to apply treatment to any of the end cuts etc.

you need to use specific fixings, nails and screws etc for pressure treated wood

Boarder1 · 01-08-2020 6:50pm

Thanks Calahonda 52. I guess I'll use pressure treated timber ( I assume Deal is ok?) followed by applications of woodstain for the aestethics. The vertical post is seated in a metal support a couple of inches above the ground. The most badly rotted section of the upright is where the two horizontal beams join the vertical post. Please see additional photo attached. I wasn't sure what type of saw to use so thanks for clarifying that. I'd been considering a mitre saw in my ignorance.

Boarder 1

con747 · 01-08-2020 7:02pm

Boarder1 wrote: »

Thanks Calahonda 52. I guess I'll use pressure treated timber ( I assume Deal is ok?) followed by applications of woodstain for the aestethics. The vertical post is seated in a metal support a couple of inches above the ground. The most badly rotted section of the upright is where the two horizontal beams join the vertical post. Please see additional photo attached. I wasn't sure what type of saw to use so thanks for clarifying that. I'd been considering a mitre saw in my ignorance.

Boarder 1

Would you consider Composite Decking for a long term fix? I have never used it but it might be a better job. I'm sure posters here can advise if it would be better.

Calahonda52 · 02-08-2020 12:54am

Well there are mitre saws where the depth of cut can be controlled, so they can be used to cut tenons, look on YOU tube.. one I know is the festool K63, there may be others

tabby aspreme · 02-08-2020 6:38am

Don't know what your budget is op, but would you consider using Accoya Larch or Douglas Fir , instead of pressure treated Deal, particularly on the vertical post and the 2 outer horizontal timbers

Kaybaykwah · 03-08-2020 7:15am

I would also investigate further to make sure there is no rot at the house end of your cantilever beams. No amount of support on the posts can prevent the balcony from falling if the inserted ends are gone. The balcony is in a very advanced stage of deterioration.

timfromtang · 03-08-2020 7:52pm

Boarder1 wrote: »

Hi,

The (unusual) outdoor balcony of my house needs to be replaced in part or perhaps in totality due to wet rot. The basic structure comprises two horizontal beams inserted into the masonry facade of the house and joined to a vertical post. The flooring is supported by joists inserted into the masonry facade. See photo attached. I'm in the process of purchasing timber. I gather that pressure treated deal (which I intend to cover with the requisite number of coats of wood preservative) will be adequate for this purpose. Is this correct? Also, can the use of wood preservative (I'm using Ronseal Woodstain) obviate the need to use pressure treated timber?

I'm a complete amateur in the area of woodcraft but intend to use tenon and mortise joints to join the horizontal beams to the vertical post I've installed mortise locks in the past so am not a stranger to chiselling! Forming the tenons will be the greater challenge. (Am I nuts to contemplate this?) I inquired at the (Rathdrum based and non amateur suffering) timber suppliers and I'd have to provide drawings if I wanted prefabricated machined timbers. I'm no draughtsman so this is outside my limited skill set.

Any insights would be gratefully appreciated.

Greetings,
Its your house
not worth skimping on,
an oak frame would be naturally rot resistant, and traditionally built with mortice and tenon construction. Oak frame buildings have proven themselves exceptionally durable over the past millennia.
Its your house
the oak framed balcony would further add to its market value no doubt should you care about such things,
just my tuppence
tim

Calahonda52 · 03-08-2020 8:04pm

Oak will be very expensive to use throughout so I would consider, at least for the big post a 150 or 200 mm sq galvanised box section, which could be faced with oak.

timfromtang · 03-08-2020 8:27pm

Calahonda52 wrote: »

Oak will be very expensive to use throughout so I would consider, at least for the big post a 150 or 200 mm sq galvanised box section, which could be faced with oak.

an expense that might be compensated for by added value to the house and a worry free lifetime fix.
How expensive are oak beams?

What about Larch?
tim

TheBoyConor · 04-08-2020 2:16pm

I'd be interested to see how the wall ends of the beams and joists are supported?
From the photo I'm getting a general naughties vibe so I would be suspecting the beam parrallel to the wall is probably beat on with express anchors maybe, or rawl bolts at best. Gripfill along the back too maybe. Then the joists running into the wall probably built into the outer leaf, allowing water into the cavity and the built in ends festering with rot.

I think this was a very poorly thought out design from the beginning - softwood deck and support structure in a private house. The designers ought to have foreseen that it would be suceptiple to rot within a relatively short timeframe and that this could, if neglected, result in collapse and injury. And it being a house, there would be a minimal chance of periodic inspection and remedial action. They should have known that eventual replacement would be led by the homeowner who, through lack of experience and knowledge, would be at risk of injury or causing injury to another from doing a poor repair or having a poor repair done by others.

If I was designing that, I'd be putting all the main structural elements in galvanised steel for robustness and longevity, and durable hardwood decking for longevity, with a galvanised 40mm square mesh underlay as a backup against fall throughs in the event that it is neglected and rots.

No thought on the principles of safety in design there. But hey, what would you expect with a celtic tiger build "designed" by the developers nephew who did a city and guilds night course in AutoCAD and all of a sudden is the architect and chief engineer of the project.

Calahonda52 · 04-08-2020 2:37pm

Building on the TBC post above, the whole thing could be built in GS like the modern apt balconies, with no thermal bridges, or in the case wet bridges

bamayang · 06-08-2020 5:30pm

You said yourself above “I’m a complete amateur”.

I’d be slow to go at a balcony without a lot of previous experience. That’s no slight on you, but balcony’s are dangerous things if not 1,000% spot on.

TheBoyConor · 06-08-2020 9:28pm

Exactly. Don't want to end up with a situation like happened those unfortunate young people in Claifornia who fell off the balcony that collapesed

Timber for outdoor use

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