Concreting on timber balconies?

[solcom]

Can I concrete over timber balconies?

I have 3 new external timber balconies, sizes 1320 x 5500mm (F17 KD Hardwood 240 x 45mm @ 450 centres) , 950 x 5700mm (450mm high engineered Floor Trusses that also support upper level of house @ 450 centres) and 2100 x 1500 (F17 KD Hardwood 240x45mm @ 450 centres). Normal 19 mm Particleboard (yellow tongue) flooring was used which needs to be waterproofed.

All balconies have a short raised wall all round which has been flashed, so drainage is via a 1 or 2 drains (using puddle flanges) located in the centre of each balcony.

<o>I have been told that to tile the balconies a mortar bed (approx 60mm thick) with fall to drains should be applied followed by waterproofing and then tiles. I know that this would add quite a bit of weight to the balconies.

<o>Is it possible to instead of tiling the balconies to just concrete them in an exposed aggregate instead of a mortar bed & tiles? Rough calculations of concrete on the 950 x 5700mm @ average thickness of 50mm would be 1/3 of a cubic meter which I think would weigh 700 kg.
<o>
Would I need to get a building inspector and or engineer to verify loads, or are all new balconies normally able to handle such weights.
<o>
Any comments or feedback would be appreciated.</o></o></o></o>

[johnc]

I think you will find you will need an engineers report and will need to talk to the building inspector about the need to get an inspection. Certainly rather than here you should be going to either the planning department or building surveyor to find out your obligations. FWIW I would not consider a concrete slab on top of a timber deck and frame, besides safety, movement would be a killer on the slab.

[manoftalent]

your best bet is to go for something like this http://www.resin-based-non-slip-flooring.com/landing-page.aspx?id=187&k=commercial%20floor

there must be a few resin based companies around to choose from and the load would be well within your range ....failing that, you would have to refit the balconies with supporting steel to hold that kinda weight ...700kg doesnt sound much ....but add four or five ppl as well and your well over a ton ...

[solcom]

I think you will find you will need an engineers report and will need to talk to the building inspector about the need to get an inspection. Certainly rather than here you should be going to either the planning department or building surveyor to find out your obligations. FWIW I would not consider a concrete slab on top of a timber deck and frame, besides safety, movement would be a killer on the slab.

Thanks for your feedback, I just don't understand what the difference is between a mortar bed & tiles as apoosed to concrete of the same thickness as the mortar bed? Won't movement affect the mortar bed also?

[Vernonv]

Was the balcony engineered to carry a mortar bed and tiles?

If so, then I would expect it's ability to carry the weight, and it's ability to withstand movement, etc, to be the same whether you are using a mortar bed or the equivalent mass of concrete.

But then again I'm no engineer :rolleyes:(not that sort of engineer anyway).

[solcom]

I am not sure if the balcony was engineered to carry a mortar bed and tiles, I would have thought that this is a standard finish for balconies and all external balconies would be engineered with this as a minimum.

[ian]

I am not sure if the balcony was engineered to carry a mortar bed and tiles, I would have thought that this is a standard finish for balconies and all external balconies would be engineered with this as a minimum.concrete balconies maybe, highly unlikley where timber bearers are used


there's lots of things to consider
GO SEE AN ENGINEER


ian

[DvdHntr]

I can't see the balcony being designed to carry 50mm thick concrete slab. That is 120kg/m2. That is over 2 layers roof tiles in terms of weight. If your calculation of 1/3 is correct it is just under 800kg.

See an engineer and be prepared to strengthen the balconies

[Sturdee]

I am not sure if the balcony was engineered to carry a mortar bed and tiles, I would have thought that this is a standard finish for balconies and all external balconies would be engineered with this as a minimum.


Go on the basis that until an engineer inspects it and certifies that it's safe to do so, it isn't. Don't assume that it was built to take such a load.

Don't forget that only last weekend a balcony/deck came away and injured a lot of people. Don't take a risk.


Peter.

[silentC]

I can't believe that they've been sheeted with particle board. The first thing I would do is replace that with cement sheet. You can then stick tiles directly to it. I don't see why you need fall to the drains if you have a bath-tub floor. I presume there's a good step down to the balcony floor from the door threshold?

What was the original plan?

Still can't believe they've been done with yellow tongue. Is that a standard practice?

[silentC]

Just had another thought. If you want to form a fall to the drain, you could use Ardex LQ 92 (http://www.ardexaustralia.com/product_display.asp?prdid=23&catid=2), which feathers out to a couple of mm and sticks like poo to a blanket.It wouldn't be any good on chipboard though, you'd have to replace that with cement sheet.

[MrFixIt]

Can I concrete over timber balconies?

Why not, that's how they used to do bathrooms in the older state housing commision houses. They would lay down the "standard" Jarrah timber floor and then pour concrete on this prior to tiling.


I have 3 new external timber balconies, sizes 1320 x 5500mm (F17 KD Hardwood 240 x 45mm @ 450 centres) , 950 x 5700mm (450mm high engineered Floor Trusses that also support upper level of house @ 450 centres) and 2100 x 1500 (F17 KD Hardwood 240x45mm @ 450 centres). Normal 19 mm Particleboard (yellow tongue) flooring was used which needs to be waterproofed.

All balconies have a short raised wall all round which has been flashed, so drainage is via a 1 or 2 drains (using puddle flanges) located in the centre of each balcony.

<o>I have been told that to tile the balconies a mortar bed (approx 60mm thick) with fall to drains should be applied followed by waterproofing and then tiles. I know that this would add quite a bit of weight to the balconies.

<o>Is it possible to instead of tiling the balconies to just concrete them in an exposed aggregate instead of a mortar bed & tiles? Rough calculations of concrete on the 950 x 5700mm @ average thickness of 50mm would be 1/3 of a cubic meter which I think would weigh 700 kg.
<o>
Would I need to get a building inspector and or engineer to verify loads, or are all new balconies normally able to handle such weights.
<o>
Any comments or feedback would be appreciated.</o></o></o></o>

I am not an engineer, however based on your stated sizes, the timber should easily support the concrete you describe. It takes A LOT of weight to snap a (vertical, ie on edge) 240mm high board. The weight of the concrete will be spread over several of the trusses so the weight should not be a problem.

You WILL of course need to ensure that the other supporting structure will withstand the weight, the "parts" holding/supporting the trusses.

What may be a problem is the "supporting" particle board. This may ultimately rot away and may result in some movement of the concrete placed on it.

I would suggest a better base on which to pour the concrete. There are some thick fibro cement boards you could use.

I would also recommend some reinforcing mesh to help the rigidity of the concrete.

[journeyman Mick]

I can't agree with you there Mr Fixit:no:, because:
"Where joists or bearers are required to cantilever to support balconies which do not support roof loads, the maximum cantilever is 25% of the allowable single span for the size and grade being used" - timber framing manual.

240 x 45 F17 maximum allowable span = 4.8M. 25% x 4.8M = 1.2M

Solcom,
your joists are already past their design load for a normal balcony, let alone one with a slab on top. I would reccomend removing the particle board and replacing with compressed cement sheeting. If you want you could top it with a proprietry cement based product to run from +15mm around the edges down to a floor waste. Don't hold any parties on your balconies. :o

Mick

[ian]

I can't believe that they've been sheeted with particle board. The first thing I would do is replace that with cement sheet. You can then stick tiles directly to it. I don't see why you need fall to the drains if you have a bath-tub floor. I presume there's a good step down to the balcony floor from the door threshold?

What was the original plan?

Still can't believe they've been done with yellow tongue. Is that a standard practice?my guess is the yellow tongue is a temporary floor to allow the ballistrades to be completed without needing scaffolding


ian

[ian]

Solcom
as Mick said
your joists are already past their design load for a normal balcony, let alone one with a slab on top. I would reccomend removing the particle board and replacing with compressed cement sheeting. If you want you could top it with a proprietry cement based product to run from +15mm around the edges down to a floor waste. Don't hold any parties on your balconies. :oand go top up your 3rd party liability insurance


ian

[thebuildingsurv]

why not use cement sheet flooring 22mm or thereabouts and pack the joist to get fall towards the front of the deck then attach a gutter to the front, this is the way its usually done.

[MrFixIt]

Hi


I can't agree with you there Mr Fixit:no:, because:
"Where joists or bearers are required to cantilever to support balconies which do not support roof loads, the maximum cantilever is 25% of the allowable single span for the size and grade being used" - timber framing manual.

240 x 45 F17 maximum allowable span = 4.8M. 25% x 4.8M = 1.2M
Mick

Yes, I agree with you there :)

I was not thinking of the balconies as being cantilevered, hence my comment...


You WILL of course need to ensure that the other supporting structure will withstand the weight, the "parts" holding/supporting the trusses.


...assuming there was some support at the outer ends of the trusses.

[solcom]

Thanks for your feedback, I think I will check with an engineer.

[solcom]

Thanks for your feedback, I ended up asking an engineer who advised that I did not have a problem with the actual weight of the concrete, but it was a bad idea due to movement and shrinkage of timber.