First Floor Balcony Details

no nails niall

Hello Folks,

Im detailing a balcony on the first floor of my house with living space under. Ideally im looking level access onto this outdoor space and intend to pave it with standard flags and no visual drainage such as aco drains.

I know flags can be laid ungrouted to allow water to drain below onto a screed laid to a fall. Does anyone know how to ensure waterproofing? Should i treat it like a standard flat roof under and lay three laters felt?

Help appreciated!

Niall

badgerhowlin

I would be interested in the reply too. Im doing the same hopefully in the near future.

sinnerboy

You need to ensure that the waterproofing surface is set down at least 150mm from your first floor. Don't consider anything other than hot troweled asphalt for this - 2 x 10mm layers with lead flashing to up stands. Then you need to allow at least 100mm for insulation. Then you need to allow at least 75mm for screed to falls.

So the structural step down is significant (150+20+100+75) and will affect the ceiling level below. Which is why so many balconies are step-over.

galwaytt

sinnerboy wrote: »

You need to ensure that the waterproofing surface is set down at least 150mm from your first floor. Don't consider anything other than hot troweled asphalt for this - 2 x 10mm layers with lead flashing to up stands. Then you need to allow at least 100mm for insulation. Then you need to allow at least 75mm for screed to falls.

So the structural step down is significant (150+20+100+75) and will affect the ceiling level below. Which is why so many balconies are step-over.

We have had to built 4 balconies in various places since........last summer, say.

What is driving this fashion ??? most seem to end up as.......ornaments.

As you say, there is a lot of detail involved. Mind you, doesn't asphalt dry out, over time ??

FarAdr

You can use a single ply membrane such as a trocal or something.. look them up. maybe put some washed gravel above and then your paving. This is just one possibility.. there are loads.. also, you do not need to use concrete to create a fall... tapered insulation can do the same job with less cost, and workmanship. You will however need to place osb or something over the insulation to create the solid substrate for the membrane... its basically tanking!Call a membrane company and they will send you out a detail or they'll be online..
Hope that help a little .

gman2k

sinnerboy wrote: »

You need to ensure that the waterproofing surface is set down at least 150mm from your first floor. Don't consider anything other than hot troweled asphalt for this - 2 x 10mm layers with lead flashing to up stands. Then you need to allow at least 100mm for insulation. Then you need to allow at least 75mm for screed to falls.

So the structural step down is significant (150+20+100+75) and will affect the ceiling level below. Which is why so many balconies are step-over.

There are lots of torch on membrane products that can be used as well as asphalt. None are inherently better than another, it's all down to correct detailing and workmanship.
In regards to some flat roof products, the supplier will give a 25 year guarantee when their approved installers are used. The approved installers are not mates or paid up members of a group etc, but just trained and approved by the product supplier.
I don't know of anyone who will give you a guarantee for asphalt to match, because it is a generic product.

Falls can be constructed by way of tapered insulation - albeit at a much higher cost than screeded fall.
The average builder on a resi job will be able to create falls with screeds very easily.
The drainage from the balcony is one of the usual areas of fail, and this needs the closest attention - as well as step up details to access back inside the house.

FarAdr

If you dont want to go down the road of tapered insulation or concrete screeds, just use timbers to create a fall, and if your looking to have level access with paving slabs these yolks can give you the rise required and can straighten up from a sloped substrate
http://www.google.ie/images?um=1&hl=en&safe=off&biw=1280&bih=595&tbs=isch:1&sa=1&q=paving+slab+supports&aq=f&aqi=&aql=&oq=

There really are so many options and as the man said above, you can get a great guarantee from a membrane.

no nails niall

FarAdr wrote: »

If you dont want to go down the road of tapered insulation or concrete screeds, just use timbers to create a fall, and if your looking to have level access with paving slabs these yolks can give you the rise required and can straighten up from a sloped substrate
http://www.google.ie/images?um=1&hl=en&safe=off&biw=1280&bih=595&tbs=isch:1&sa=1&q=paving+slab+supports&aq=f&aqi=&aql=&oq=

There really are so many options and as the man said above, you can get a great guarantee from a membrane.

FarAdr,

These are the things I saw detailed on a site last week. They were placed on a sloped screed with ungrouted paving slabs above.

In such a situation is the membrane laid in a tanking detail style with lead flashing before the sloped screed is laid.

I'm considering using insulated plasterboard on the ceiling under the balcony to get the required u values.

Niall

gman2k

Niall, You need to give us more detail on your construction.
Do you have precast on block walls for example? - I'm taking by your ref to screed that this is your construction.
Also, The best form of flat roof construction these days is considered to be warm roof construction, where the insulation is at the outside of the construction, or just underneath the waterproof membrane.
The waterproof membrane whether a torch on material or asphalt will be over the sloped screed.
In general terms you will have your PC slabs, screed to falls over, insulation to give req U-value and then your waterproof layer. The exact build up will be determined by your choice of waterproofing.
Your lead flashings to upstands will flash over the waterproofing layer, and should have min 150mm vertical cover. Your lead flashings should be installed before you start any tanking procedures take place.
Paving slabs can be laid unscreeded very easily on a flat roof construction. They are generally supported on proprietary adjustable plastic legs that take into account the sloping construction below.
Rainwater falls on the flat pavers - runs to the c. 10mm gaps (ungrouted) and falls to the waterproof sloped layer below where it will fall to some form of a drainage trap.

no nails niall

gman2k wrote: »

Niall, You need to give us more detail on your construction.
Do you have precast on block walls for example? - I'm taking by your ref to screed that this is your construction.
Also, The best form of flat roof construction these days is considered to be warm roof construction, where the insulation is at the outside of the construction, or just underneath the waterproof membrane.
The waterproof membrane whether a torch on material or asphalt will be over the sloped screed.
In general terms you will have your PC slabs, screed to falls over, insulation to give req U-value and then your waterproof layer. The exact build up will be determined by your choice of waterproofing.
Your lead flashings to upstands will flash over the waterproofing layer, and should have min 150mm vertical cover. Your lead flashings should be installed before you start any tanking procedures take place.
Paving slabs can be laid unscreeded very easily on a flat roof construction. They are generally supported on proprietary adjustable plastic legs that take into account the sloping construction below.
Rainwater falls on the flat pavers - runs to the c. 10mm gaps (ungrouted) and falls to the waterproof sloped layer below where it will fall to some form of a drainage trap.

Gman,

Proposed structure is precast hollowcore slabs with end bearing on 215mm quinnlite blocks.

Struggling a bit to get the depth that gives me suitable headroom in the room below while also allowing for 150mm vertical cover.

Currently I have drawn: 35mm paving slabs (350x350) on plastic supports, on waterproof membrane, on tapered insulation on hollowcore slabs.

Can a membrane be hot applied to rigid insulation? I haven't got the depth to apply a concrete screed.

Thanks

Niall