Drainage requirement for gable wall

[gravelld]

We have just installed a 4.5m slider into the ground floor of a gable. One floor above, with the gabled roof above that.

 

With bad rain and wind we're getting some water ingress underneath the door. We need to seal this, but it looks like part of the problem is when a quantity of water sits at the bottom of the door and gets blown in. So I think as well as sealing the hole, we should allow for water to drain away more quickly. Is this right?

 

Two obvious solutions are suggested:

 

- A French drain with a pipe at the bottom attached to downpipe

- A French drain which is just a ditch with no connection to a downpipe

 

The former is obviously better drainage wise, but it's double the cost. Also, I intend on externally insulating the house (including the founds), which means such a solution would be wasted; we'll have to move the drain away from the wall later.

 

So, is there a way of calculating how much of a ditch volume would be required? There's no run off from the roof, it's just a gable wall (often facing prevailing wind).

[Oz07]

I often think surface water drainage requirements as a bit heavy. For instance before the house was there water drained away. I'd perhaps just use a gravel filled French drain for now perhaps digging so there is a section which takes water away from the founds and gets deeper

[Russell griffiths]

[gravelld]

Thanks for these ideas/thoughts.

[joe90]

Is the water going under the track? Does the track have a drain hole? Ours does, and I piped it to a French drain. I like @Russell griffiths pic above, neat solution.

[gravelld]

It's below that - the track and threshold sit on a timber member with the DPM underneath that. It's in-between the water is getting in.

 

Outside there's a Siga weather proofing tape but this is currently just flapping about and needs to be lapped down into the trench and sealed above between the tape and the cill.