Dave's Balcony

[ProDave]

I am turning my thoughts to my own balcony, not to be confused with Zoot's balcony, though a lot of the principles will be similar.

 

Here are a few design constraints.  The balcony will be about 4.5 metres wide, it can't be much wider than this otherwise it would intrude on the landing window.  It will extend perhaps 2 metres out from the house, that is open to debate, but enough room to put some chairs and a table to sit out, and to be able to pass the outward opening door when it is open.

 

It will be planked with decking planks, set to a slight fall for rainwater to run away from the house. That dictates decking planks perpendicular to house wall, so joists running parallel to the house wall.

 

A fixed parameter is the bases to sit the support posts are already in place, they are at 4 metre post centres and the posts are 1.4 metres out from the house wall.  That is deliberate The idea is the posts will take more than half the weight of the balcony, but more that half way out from the wall.

 

Where it fixes to the wall, it will be spacers and long coach bolts so the joist adjacent to the wall is not touching the wall but spaced off a little.

 

This is a general view of where it will go.

 

 

And these are the post supports, concrete blocks cemented onto concrete pads that were poured at foundation time and have only just been uncovered again.  The blocks are to ensure, particularly for the right hand post, that the bottom of the posts and the post shoes are above ground level.  That will all then be covered with decking so it does not matter these don't look pretty.

 

 

And here is version one of the frame construction.  The longest span is 4 metres so I will probably use 8 by 2 joists.

 

[joe90]

Looks good to me!, have you thought about composite decking that last longer and does not decay and rot like wood? (I have just replaced my brothers decking due to rot, but it did last 14 years 🤷‍♂️.

[ProDave]

Composite decking planks is a possibility, it depends how much extra it costs compared to wood.  We will have a lot more decking to do at ground level as well as the relatively small amount of decking planks on the balcony.  and then there is the bridge over the burn, one of the last projects........

 

Apart from the joist size question, I want advice on post size.  Thinking of 6 inch square posts (150mm for our younger readers) but at the moment have not even tried looking for any, nor actually measured how long then need to be.

[AliG]

I have coined a phrase recently -

 

I am not a structural engineer but...

 

it looks alright to me.

 

What kind of rails are you planning? It might affect the outside edges.

 

Please feel free to use "I am not a structural engineer but" in any situation where you give an opinion even though you don't actually know what you are talking about.

[ProDave]

Banister / rails is a topic for later, but worth a thought and mention now.

 

We would like glass.  But to buy a "glass rail system" is expensive.  I am thinking along the lines of what I saw on a new build that I wired.  They just bought plain sheets of toughened glass, and used 4" wooden posts with a groove routed down each opposing side for the glass to slot into (adjacent sides for the corner posts).  And a 4" posts would rebate nicely over 2" joists and bolt to them.  A wooden handrail round the top further ties it all together.  Extra noggins between the outer joist and the next one in where the posts attach to stiffen it all up a bit, not currently shown on the plan.

[markc]

Posts with alu channel works well too (great for steel posts) slide glass in and silicon or mastic to fix in place

[Bonner]

2 hours ago, ProDave said:

Apart from the joist size question, I want advice on post size.  Thinking of 6 inch square posts (150mm for our younger readers) but at the moment have not even tried looking for any, nor actually measured how long then need to be.

Are you thinking oak? I would have thought 6” softwood would be a bit too flexi. I would go for 8” posts in any case just because they would look more substantial.

[ProDave]

5 minutes ago, Bonner said:

Are you thinking oak? I would have thought 6” softwood would be a bit too flexi. I would go for 8” posts in any case just because they would look more substantial.

that's the sort of feedback I am looking for.  I have just measured and reckon the posts would be about 2.3 metres long.  What do others think?  I am not against 8" or even 6" oak posts, but fear they will not be cheap.

[SteamyTea]

3 hours ago, ProDave said:

It will be planked with decking planks, set to a slight fall for rainwater to run away from the house.

Posh flats in PZ have plank decking.

Rain filters though the cracks in them, then drips for hours after a short shower.

 

2 hours ago, AliG said:

I am not a structural engineer but

I am not a drainage engineer, but I would look at an imperable base and some sort of conceled guttering and drainage.

 

I am also not a house designer, but often I see balconies with walls on them, so when sitting in a chair you cannot see over them.

So glass, which I think looks really naff and passersby can look up your kilt.

[Jacob]

Please don't forget the splash zones on the render , baumit are quite particular about the render getting wet 😜 maybe have a 150mm deck upstand close to wall ? 

[Modernista]

3 hours ago, ProDave said:

Composite decking planks is a possibility

Been quite disappointed with our composite deck.....it's only done one Scottish winter and seems to have some frost damage where moisture retained in the grooves has frozen and opened up a split in an odd plank here and there....so I'm heading for changing my mind on composite decking I think.....

[ProDave]

2 minutes ago, Modernista said:

Been quite disappointed with our composite deck.....it's only done one Scottish winter and seems to have some frost damage where moisture retained in the grooves has frozen and opened up a split in an odd plank here and there....so I'm heading for changing my mind on composite decking I think.....

What exactly is "composite"?  I have always taken it as a posh name for some meaning some form of plastic that looks a bit like wood but it won't rot.  The fact it has frost damage is indeed disappointing. We get a lot of frost here.

[JohnMo]

I just purchased a lot of ultra signature composite decking planks, they come with a 25 year warranty, so hope I don't get an issue.

 

[Onoff]

What about a couple of decent telegraph poles as possible cheap posts? You could machine square faces at the top to fix through. Black to match your downpipes.

 

Be careful sliding glass straight into wood. Any warpage will crack the glass. Better to have an intermediate "channel" to deal with expansion. You can of course recess the channel flush with the balustrade uprights. 

[joe90]

35 minutes ago, Onoff said:

Be careful sliding glass straight into wood. Any warpage will crack the glass.

Another reason for using old wood (poles) as by now they will not warp anymore, plus poles are made of very straight grained wood and rarely twist or warp.

[saveasteading]

13 hours ago, ProDave said:

plain sheets of toughened glass, and used 4" wooden posts

I wouldn't know where to start in knowing if the glass was suitable for the purpose, so would probably have enough framework to prevent falls, and the glass to keep out the wind and allow vision.

I assume this is subject to building warrant, so how could you prove it?

 

There are better value steel and glass balcony systems recently, especially if in standard sizes, which you could design for.

 

'Composite' is recycled plastic, bulked out with sawdust. Works well and is very durable, but gets very hot in the sun, which of course is a big concern where you are.

We bought a picnic table of the stuff, and it is going strong after 15 years, which timber would not.

[Gone West]

We used 10mm clear perspex in our balcony. Lighter and easier to handle than glass.

[ProDave]

The glass subject will be discussed later.  I was expecting once I know sizes to get advice on thickness, laminated or toughened etc then go to the local glass supplier.  Perspex may work but has a habit of scratching / going cloudy so while it may be cheaper and lighter, it may need replacing after a short while.

 

The issue of the post warping and breaking the glass is solved by making the groove wider than the glass so it is not a snug fit and bedding it in clear sealant.

[Onoff]

6 minutes ago, ProDave said:

making the groove wider

 

I'd suggest deeper too. For running a strip of "rubber" up there first so the edge of the glass has rubber on 3 sides.

[Mr Punter]

I have steel framed cantilevered balconies, galvanized and powder coated, with obscure glazed balustrade and ipe decking fixed to iroko joists and with stainless steel handrail.  They are about 2.9m x 1.5m.  Cost was horrific at over £6000 each.

[Gone West]

7 hours ago, ProDave said:

Perspex may work but has a habit of scratching / going cloudy so while it may be cheaper and lighter, it may need replacing after a short while.

Perspex is softer than glass so scratches more easily, but also polishes out easily. It doesn't go cloudy, you may be thinking of polycarbonate. Before deciding to use Perspex I read that there are pieces of perspex from WW2 aircraft canopies that are still clear.

[Modernista]

18 hours ago, saveasteading said:

'Composite' is recycled plastic, bulked out with sawdust. Works well and is very durable, but gets very hot in the sun

Yes, but our composite is fitted with the suppliers clips all to their instructions and I'm not sure that approach gives enough expansion gap as quite a few of the joints closed up tight and perhaps that's why ours has split as shown in pic - although it seemed to happen after the winter so I'm still thinking frost. We live amongst trees so quite a bit of leaf debris etc clogging grooves and possibly retaining moisture (yes we could sweep and clean more but it would be an hourly job!) It's put me off enough that I've switched back to wood on another deck recently done at the front.

[Simplysimon]

as on another post, composite posts at 3m, this would allow you to continue it up past the deck height as a corner post for handrail. if it was possible to to keep at or above 800mm above the deck then  you would be close to 900mm for handrail.

BTW as you're now north of the wall noggins become dwangs 🙂 

[SteamyTea]

14 hours ago, Gone West said:

Perspex is softer than glass so scratches more easily, but also polishes out easily. It doesn't go cloudy, you may be thinking of polycarbonate. Before deciding to use Perspex I read that there are pieces of perspex from WW2 aircraft canopies that are still clear.

Perspex is acrylc, so, in its natural formulation, will stay clear.

There are two main types of acrylic sheet, cast or extruded.  Avoid extruded.

You can get flexiable acrylic sheet, which offers better shock resistance, but I have no idea what the long term exposure to UV is like, it has nano particles of rubber in it.

[JohnMo]

But perspex will look rubbish, unless it's thick, so it doesn't flop about in the wind.  But it scratches easily, thick perspex is a similar cost to glass, last time I looked, a couple of years ago.