Soil against wall ?

[DERYN]

Hi everyone, I've been busy checking out cottages with a view to buying and I've noticed something worrying with a few ! On a few of the cottages the land/soil at the rear is built, or has built up over the years, halfway up the wall ! This of course has led to dampness inside the properties. I'm guessing that in some cases it might have been deliberate to guard against the elements ? Hence no windows below the soil level ! In a building a hundred or more years old I'm not sure what damage this will have done to the actual building material.

In such instances if you wanted to improve matters would you dig out, check the condition of the building materials, and then treat the wall with 'something', and place some kind of membrane between the wall and the soil ?

Or would you remove the soil from the wall and a distance from the wall make an area level with the ground area at the front of the building ?

Anyone had a similar experience ?

DERYN

 

[MattW]

if there is a serious problem with damp from exterior soil levels, the most commonly recomended solution is to lower the ground level in the area near the wall (i.e. exposing the house wall to air not soil). I doubt that an exterior membrane in In many cases would be advisable as it will trap existing moisture in the walls. If you can lower the ground level over a wide enough area, then you should consider french (or english) drains. on another thread Dave Briggs gave this explanation:

FRENCH DRAINS
One of the most recommended solutions for reducing damp at the base of walls and floors. Putting the word 'French' in front adds a touch of class to what is in effect a ditch filled with gravel. Key things to remember are:
1. The bottom of your french drain should be several inches below the base of the wall
2. It must be properly drained, to prevent it turning into a moat and making the damp worse. If your house is built on sand, the drain may drain without any help. If the soil has more clay you will probably have to add lengths of suitable diameter pipe, drilled with regular spaced holes facing downwards. This will collect water, which will then need to be fed away from the house. Needless to say, drainage is easier if the ground does not slope upwards away from your house.
3. Take care when disturbing the ground at the base of your walls. Unless you are confident about foundations, dig your french drain a little away from the wall, and angle the sides.

if the ground level is very high, you might to build a brick/stone retaining wall parallel with the house down to foundation level, and put the drain in front of that so that water will come through the retaining wall and then flow down into the drain, rather than attempting to building an 8' deep ditch which would be impossible.

 

[MdB]

In our back garden the slope is towards the house and this apparently caused rain water to puddle up against the house. Their solution was to build up the soil next to the house so the rain ran away from the house. It did of course mean that all it did was leave a pile of damp soil up against the wall causing major damp problems inside of the house. One of the first jobs I did here was to remove some of this soil (though I must admit there is still one section still to do.)

Best solution is to remove the soil. Next best is to dig a gully next to the wall which drains away. You can then consider a french drain or a system designed for this job (no idea what it is called but it looks like large corrugated plastic).

 

[Stephen]

I am not in favour of traditional French Drains because they leave the wall with something against it and therefore still unable to breathe.

Whilst it is not always possible I prefer to create a channel. See sketch below (not to scale) - this is only a rough guide, but hope it helps.

Stephen

 

[MdB]

The base of our neighbours house is below the local ground water table and they use Stephens channel method together with a pump. Seems to work well for them.

 

[Flyfisher]

In a building a hundred or more years old I'm not sure what damage this will have done to the actual building material.

This will, of course, depend on the building material. It's the sort of thing that can badly affect a timber-frame but will have less effect (probably none) on anything brick.

Ventilation is the enemy of damp. Expose the wall to the air somehow and the problem should cure itself. This may be easier said than done, depending on the grounds around the property, but is something to bear in mind when looking to purchase.

 

[Penners]

would you dig out, check the condition of the building materials, and then treat the wall with 'something', and place some kind of membrane between the wall and the soil ?

Dig out, yes. Treat the wall with something, absolutely not. Just let the air get to it and dry it out naturally.

Stephen's description above is absolutely definitive (and he's a professional in such matters).

use Stephens channel

And thus a new term enters the PPUK lexicon. Not a French drain, but a Stephens channel. :wink:

 

[DERYN]

Brilliant, thanks guys. That answers my questions perfectly and I'll be sure to print the info.

DERYN

 

[FamilyWiggs]

Hmm - am beginning to think I need to deal with the rear half of my property which is on a slope and has high ground levels in a number of places. The side facing the prevailing wind is cement rendered, which is now coming away from the wall in sheets and I am sure is linked to the base of the wall being buried a few feet.

My question though is how far down should/could I excavate for the drain. I'm worried that the wall extends down about 18-24 inches below internal floor level and is laid directly onto the soil, albeit with some hefty large stones at the base. Can I excavate to the base, but no further. Less than the base, or just below internal floor level?

Thanks

 

[Stephen]

In the past I have devised a system of a channel at the rear with a drain gully at its base and drainage pipes running around the building to discharge the water downhill of the property. In other words you capture the water between the hill and house and re=direct it around the building to let it discharge on the downhill side/s.

Stephen

 

[rebeccac]

I like the idea of the channel particularly as our house is on a downward slope so its easy to divert water into a garden area.At the moment the soil is above floor level.

But the house that joins ours is abandoned and the roof is old with no guttering.When it rains rain pours off onto the grass verge and I presume finds its way under our house as it is above us on sloping ground.

I stupidly stated before 2008/2009 was the worst winter in Abruzzo ( Italy ) for 200 years now we are faced with another worst in 200 years winter!!!!I have not been out yet but I'm confident that it will be wringing wet!o what can we do about the neighbours side? Any bright ideas?

 

[davidward89]

I am not in favour of traditional French Drains because they leave the wall with something against it and therefore still unable to breathe.

Whilst it is not always possible I prefer to create a channel. See sketch below (not to scale) - this is only a rough guide, but hope it helps.

Stephen

Hi, is there anywhere of seeing this diagram? It's no longer available. Thanks

 

[Kearn]

If you can lower the ground level over a wide enough area, then you should consider french (or english) drains.

I think the late American, Henry French might be less than keen on you changing his surname…!

I also don’t favour French drains for what it’s worth - there is always wet material against the building which fills with decaying matter over time regardless of a membrane. The perforated holes in the pipe get clogged and even if they don’t, the ratio of hole to no hole is daft to try and shed any significant water through the pipe. Which itself is usually under sized and without enough fall. Plus it needs somewhere to soak away/run off.

Easier to use a permeable materials, like gravel and ensure a fall from the building…

While excavating an inital channel around our perimeter. I just dug a moat!