french drains

[jason61c]

I've one damp wall left to sort.

Concrete render stripped off wall, exposing the stone, external ground level(which isn't mine), is about 6" higher than the level of the floor inside. The floor is timber suspended on 3 brick high dwarf walls

Its only a bit of gravel between my next doors garage and my house(5ft wide).

If I dig down 18" I hit hard sand.

I can put a french drain both sides(inside the house under the floor) and on next doors patch.

How deep does it need to go? How far away from the wall is best?

 

[theprinceofdarkness]

You have not said at what level the DPC is. No point in putting a french drain inside the house, the pebbles are mean't to allow the water to evaporate. Have you got underfloor air vents?
Frank

 

[jason61c]

It doesn't have a DPC.

I can put a drain under the floor as I can have it 'flow' outside, I understand they don't allow water to evaporate.

I've had the floor open to the room for about a year. The only damp is on the one wall and the floor is bone dry underneath once you're 3ft away.

 

[ree]

Why dont you post pics of all the areas mentioned above?

Have you examined all joist tails sitting on or in brickwork?

Spreading a Membrane over the oversite and lapping it up the walls 100mm will keep down condensing moisture.

Do you have any solid floors?

 

[jason61c]

Hi Ree.

I do have some solid floors, they're further up the house though. They're coming up and i'm putting limecrete down with GLAPOR Foamed Glass underneath.

I've just finished digging along. There use to be a workers cottage attached(circa 18th century), its gone, I've found the bottom of the wall, everything I've dug out has been very loose and soft, giving zero support to the wall. The sand underneath is amazingly compacted though. I guess that's why it's stood so long.

The first pic is after 6" of hardcore to the bottom of the fabric.

There's one of the inside.







floors are at 17" inside, subfloor base is at about 8".

 

[ree]

1. First off this looks like a case of getting in a SE? Dont do anymore digging (anywhere) let a SE have a view.

2. Your 2" x 4" joists appear to sit on plates over timber beams.
The two joists in the c/breast recess appear to have decay and have been packed up.

3. You have some neat looking, well applied Tyrolean render - is the inside of that wall dry?

4. Could you get the neighbour to agree to lowering the high ground level? Quite how low is difficult to know, care must be taken not to de-stabilise the "foundations". Dont do any digging inside the wall.

5. I dont know how far you are going but the hearth area might be a source of dampness and fungal decay - its only a possibility.

6. The built-up chimney breast recess might be allowing rising and penetrating damp.

7. What kind of air bricks (if any) do you have?

8. Do you have underfloor ventilation?

9. The best practice for plastering in your situation is to knock off all earlier plasters, and render in sand & lime.

10. FWIW:
Remove all rubble from site as soon as its produced.
Remove all proud nails from joists - immediately.
Clear the work area of everything thats not in immediate use.
Dont lean props - lay them down.
Mark all your floor boards as you lift them.

 

[jason61c]

Hi

1. First off this looks like a case of getting in a SE? Dont do anymore digging (anywhere) let a SE have a view.

Hi, no need for a SE, I've had a few round over the past 18months, why do you think there's a need?

2. Your 2" x 4" joists appear to sit on plates over timber beams.
The two joists in the c/breast recess appear to have decay and have been packed up.

Hi, there's no decay, they're on the original sole plate on top of the dwarf wall?

3. You have some neat looking, well applied Tyrolean render - is the inside of that wall dry?

That crappy render is the largest part of the problem, its the other side of this wall. It was 1" into the outside ground level, I've removed it all from the
original stone to let it dry out and do its job.

4. Could you get the neighbour to agree to lowering the high ground level? Quite how low is difficult to know, care must be taken not to de-stabilise the "foundations". Dont do any digging inside the wall.

I'm going to ask if I can, we get on well, even if I can it'll only be by about 8", which will help. I'm going to put 40mm stone next to the wall so no moisture is held against it if I can't lower it.

5. I dont know how far you are going but the hearth area might be a source of dampness and fungal decay - its only a possibility.

Its dry as a bone, what you can't see is that that wall(gable end) floor level is about 6 ft over outside ground level

6. The built-up chimney breast recess might be allowing rising and penetrating damp.

Yet again, all dry as a bone

7. What kind of air bricks (if any) do you have?

None yet, they're going as this room goes back together.

8. Do you have underfloor ventilation?

As above, I'm going to put vents in the gable end and the south facing wall and allow cross ventilation by putting air bricks in the dwarf walls

9. The best practice for plastering in your situation is to knock off all earlier plasters, and render in sand & lime.

I've removed all gypsum plaster and lime plaster thats had paper/none breathing paint. That wall has lovely lime plaster with a limewash finish.

10. FWIW:
Remove all rubble from site as soon as its produced.
Remove all proud nails from joists - immediately.
Clear the work area of everything thats not in immediate use.
Dont lean props - lay them down.
Mark all your floor boards as you lift them.[/QUOTE]

All boards have been marked
All rubble is removed the day it gets there
everything in the pic has been used today
I'm not going to remove nails until I can see the whole joist is still in good condition incase its a waste of time.

Thanks for you comments, good to know i'm going at it the right way

 

[cAtLeYx]

I agree with Ree regarding the excavations, (Yes I did just say it) ) whilst I appreciate you have advised the ground was "very loose & soft" its not advisable to expose the lower levels as the now exposed face and reduced ground level could dry out and shrink.

 

[jason61c]

Well the ground seemed to be about 10" of coal!? Did dig up a few old bottles, 1" thick quarry tiles, lots of animal bones also.

 

[cAtLeYx]

Animal Bones - Its not Fred West's old house is it?

 

[jason61c]

Pig and goat, the room in the pic has lots of cow bones in the floor. Dry as a bone