Balcony Floor - Rain Pouring Through

[dk1uk]

Hi all - the house I've just moved into has a small first floor balcony. Its floor is made of decking.

However, I noticed over the past couple of days as it's raining, the water is coming through the underside of balcony (which has down-lighters in it!!). I took up a couple of the decking panels and it seems that whoever built it didn't think to attempt to make the floor waterproof - the have basically screwed decking straight onto the joists that make the balcony.

I was thinking of buying some roof felt; taking up all of the decking and nailing the roof felt to joints to waterproof it, then laying the decking back over.

However, I'm not sure on 3 things:

- Is this the best solution?

- How would I join the felt to the house wall to ensure water doesn't seep through? Could I seal the gap with roofing mastic?

- One concern is that water will gather on the felt and if it's covered with decking, then it would be able to evaporate away so potentially I end up with decking sitting in a pool of water - is this a valid concern?

I'd appreciate any views on this.

Many thanks.

 

[cotswoldbuilders]

The roof covering goes over the decking, not under.
Remove all existing down to joists, check you have a fall, lay new decking.

Finish with material of choice, ie felt, lead, glass fibre, epdm.

To seal to house you need upstands with lead flashings chased into the wall.

You can get roof tiles or walk way pads to lay over the finish roof covering.

 

[^woody^]

The roof covering goes over the decking, not under.

If its a balcony then the felt will be under the decking boards so that no-one walks on the felt

 

[dk1uk]

Many thanks indeed for the replies. Yes I would rather have the decking over the waterproof layer only because it looks nicer. Is there likely to be any issue with that, especially since the decking would sit on top of the felt?

Pardon the naive question, but when you say 'check you have a fall' - what is a fall?

Many thanks.

 

[^woody^]

You can have a timber deck on the felt. Just ensure that any timber touching the felt has no pointy corners or edges which can dig into it, and that the timber bearers don't impede drainage

A "fall" is the slope

Just re-reading cotwold's reply, I think he is referring to the actual roof deck which does go under the felt, and you are referring to decking boards like you have in the garden

 

[TonyW2]

Edit---slow typer
I think there is cross-use of the term decking!
Decking in flat roofing refers to (plywood) surface over the beams and this is covered by waterproofing felt layer.
Seems as though OP has wooden (garden type) decking laid on top of this with nails penetrating the waterproof layer.
Could this top decking be fitted to battens loose laid on roof to produce a wooden mat?
Fall is a slope, organised so that water flows off the roof.
The felt would need turning up the wall and then covering with a (preferably lead) strip secured into the wall at a mortar joint.
A roofer could do this with hot sealants and should not be costly for a small balcony

 

[dk1uk]

Hi - yes you're right, it's decking like the type you'd lay in the garden. So I'll nail the felt to the joists; and screw the (garden) decking back into place over the decking.

I can't think how I'd make a slope, though I'll check with a level as the balcony may have been built with a fall in the first place.

Thanks for your help - guess what I'm doing next weekend

 

[^woody^]

So I'll nail the felt to the joists; and screw the (garden) decking back into place over the decking.

I don't think you want to be nailing. It would be better to stick the felt down

And don't screw the decking through the felt!

 

[freddiemercurystwin]

Wot about them big felt nails like wot you would get for a shed roof, they'd be sure to seal the roof from any water ingress ^woody^?

 

[^woody^]

Yes, but a shed roof would normally be on a bit more of a slope. Yes the clout nails may self seal, but perhaps not the best thing for a nearly flat balcony?

It might be OK, but I'd say not ideal unless there is no other option

 

[freddiemercurystwin]