damp under the floor

[Joss]

We have recently had a new water supply pipe installed.  Where it comes into the house, there is a wet patch.  Two weeks later, and it shows no signs of drying out despite not having a floor in that room and plenty of ventilation. Is it the sort of thing that might take months to dry?  Would I be alright to insulate and replace the suspended timber floor, or should I leave it open longer?

[markc]

What level is this compared to outside ground level?

[Joss]

Ground level inside is 3 bricks below damp course, ground level outside is currently only 1 brick below damp course (plan to lower this later this year), so ground level inside is about 6 inches below ground level outside. 

 

[Joss]

Not sure if it is significant, but there is a down pipe outside, off to one side of the damp patch.  The underground drain comes away from the house at an angle (off to left of photo).  It is not blocked.

[Marvin]

I would expect the drain to spill over when used. look at all the marks on the wall the moss. If that's a rainwater down pipe, next time it rains have a look or pour a bucket of water into the down pipe and see what happens. I bet it bounces off the concrete bottom of the drain and goes everywhere...

[markc]

42 minutes ago, Joss said:

Ground level inside is 3 bricks below damp course, ground level outside is currently only 1 brick below damp course (plan to lower this later this year), so ground level inside is about 6 inches below ground level outside. 

 

I thought as much, water is entering the ground either directly or splash as noted above and then finding its way in through the hole. I would dig out and seal around the duct and pipe to prevent water having any easy path to the inside.

[Joss]

Thanks for your replies.  I will check with the installer whether pipe and ducting are sealed. 

Water does not splash out of the brick surround on the drain, but I think is probably getting between the mortar and wall sometimes. What is the best way to ensure that it goes down into the drain better?

[Mr Punter]

6 minutes ago, Joss said:

What is the best way to ensure that it goes down into the drain better?

 

You could put a shoe on the downpipe so directs the water away from the wall.

[jayc89]

The downpipe wants extending beneath the grate. If it's anything like ours was, it gets filled up with leaves and other crap too easily and with heavy rain overflows anyway. (I also mixed up some cement to fill the gaps between the bricks and the wall. )