Advice on height of gravel zone next to house

[data72]

Hello lovely community!
we have a stone cottage above ( 100 years old) and there was some dampness coming into the bottom of a wall from one of the rooms.
Turns out the garden bed just outside the property had soil levels that were higher than the internal floor level and a rose was growing into the wall. So ..soil was reduced to level lower than internal floor , any vegetation growing into wall was removed
BUT THEN then for future prevention of this recurring we thought of the following:

We thought to put a layer of gravel (with drainage pipes feeding into existing drainage system) at the back of the garden bed surrounding the house, closest to the house walls.
This layer/slice of gravel in the garden bed surrounding the house, would act as a boundary between the garden bed soil ( on the one side of the bed and the house wall, on the other side of the bed)

SO ...the garden landscaping company dug out a trench around the exterior walls (within the existing beds) They placed treated timber edge as an outer boundary between the gravel and the soil of the bed. While we were away, they then proceeded to fill the trench with gravel

HOWEVER the problem is that they raised the gravel border height to be higher than the internal floor level. In areas it is more than 10 cm higher.

CONCERN/QUESTION : with what they have done, will it lead to the outside of the wall getting damp every time it rains (and it rains a lot on the IOM) The landscapers claim that it should not be a problem because it will drain away. However it does not make sense to us Why risk any damp by mismatching the gradient between outer and lower floor levels?
In your experience what do you think? Are we overreacting? Or have they made a mistake? If they have how should it be corrected?

 

[Toby Newell]

This seems a bit bizzaire, lazy design I guess. I can see they want a uniform height between gravel and the bed but why go to the troube of digging a trench only to raise the ground level? Gravel holds far less water than earth but it will hold some and wick that to the wall. Why did they need a mini raised bed anyway? They could of sunk pavers flush if the wanted to make a deliniation. And treated timber? Laid into soil? Lol, that will rot. Treated lumber I get from merchants that is kept outside (under cover) often already has green mold. Unless they treat it with creosote the bottom will rot fairly quickly. Pressure treatment is a percaution, its not a magic cloak.

Seeing as it's gravel it will probably be ok, but the design is lazy and unnecessary.

 

[data72]

Thanks for taking the time to respond.
I agree . I don't see the logic to build a trench and then raise the ground..
If this was your house would you have them redo it?

 

[Toby Newell]

I don't know, there is a damp expert chap Matt that has just logged on, I have worked on period properties as a conservator and restorer for 30 years but am not a damp expert.

I guess it's a matter of degrees, gravel drains an order of magnitude better than soil so I would guess it should be ok. If your damp issue is pervasive then you may have to revisit it.

It just piques my curiousity why one would take 3 steps forward then one step back. The addition of the timber sunk into the earth suggests to me these guys don't seem like the A team.

I think they are raising the border for aesthetic reasons and also possibly to save themselves from digging down as they can just plonk topsoil on top.

Actually thats probably it lol, it looks like they may have dumped the spoil from the trench mostly onto the raised bed part, saves then barrowing the spoil away and drom digging out the border to fill with new topsoil.

I think it's probably ok. If you get damp issues you know what it is. Don't think that wood will last all that long though.

 

[Zebra]

I largely agree with the above. If the gravel is deep enough then it'll probably be OK, but does seem like why do it like that....
The problem with gravel as I found out, is that although it's free draining, it doesn't allow evaporation. If you scrape away the top layer, the gravel will be holding some moisture - not as much as soil, but the stones won't be dry.
Here I had to remove the gravel altogether and have free air, but I was dealing with very porous and absorbent soft red bricks. I don't know how porous and absorbent your stone would be. I think it comes down to "try it and see..." But if it were me, and that gravel went down a ways, I'd be scraping some off the top.

 

[data72]

I largely agree with the above. If the gravel is deep enough then it'll probably be OK, but does seem like why do it like that....
The problem with gravel as I found out, is that although it's free draining, it doesn't allow evaporation. If you scrape away the top layer, the gravel will be holding some moisture - not as much as soil, but the stones won't be dry.
Here I had to remove the gravel altogether and have free air, but I was dealing with very porous and absorbent soft red bricks. I don't know how porous and absorbent your stone would be. I think it comes down to "try it and see..." But if it were me, and that gravel went down a ways, I'd be scraping some off the top.

Thank you for your thoughts. Much appreciated

 

[data72]

I don't know, there is a damp expert chap Matt that has just logged on, I have worked on period properties as a conservator and restorer for 30 years but am not a damp expert.

I guess it's a matter of degrees, gravel drains an order of magnitude better than soil so I would guess it should be ok. If your damp issue is pervasive then you may have to revisit it.

It just piques my curiousity why one would take 3 steps forward then one step back. The addition of the timber sunk into the earth suggests to me these guys don't seem like the A team.

I think they are raising the border for aesthetic reasons and also possibly to save themselves from digging down as they can just plonk topsoil on top.

Actually thats probably it lol, it looks like they may have dumped the spoil from the trench mostly onto the raised bed part, saves then barrowing the spoil away and drom digging out the border to fill with new topsoil.

I think it's probably ok. If you get damp issues you know what it is. Don't think that wood will last all that long though.

Hello Toby.

I don't know, there is a damp expert chap Matt that has just logged on, I have worked on period properties as a conservator and restorer for 30 years but am not a damp expert.

I guess it's a matter of degrees, gravel drains an order of magnitude better than soil so I would guess it should be ok. If your damp issue is pervasive then you may have to revisit it.

It just piques my curiousity why one would take 3 steps forward then one step back. The addition of the timber sunk into the earth suggests to me these guys don't seem like the A team.

I think they are raising the border for aesthetic reasons and also possibly to save themselves from digging down as they can just plonk topsoil on top.

Actually thats probably it lol, it looks like they may have dumped the spoil from the trench mostly onto the raised bed part, saves then barrowing the spoil away and drom digging out the border to fill with new topsoil.

I think it's probably ok. If you get damp issues you know what it is. Don't think that wood will last all that long though.

Hello Toby. How can I reach out to matt the damp expert? I am new to this forum. Also instead of wood, what would you have used? Is there a slim ish long lasting material to seperate the 2 materials ie gravel and soil?

 

[Toby Newell]

Hello Toby.

Hello Toby. How can I reach out to matt the damp expert? I am new to this forum. Also instead of wood, what would you have used? Is there a slim ish long lasting material to seperate the 2 materials ie gravel and soil?

He just was on here, he might pop back and answer, its pretty basic tbh. The gravel level should be at or below floor level so this installation is incorrect, this is crushingly obvious. As I said your operatives did it to save work in removing spoil and digging for border top soil, adding a bit of wood is the cherry on the top.

Exactly as Zebra states, gravel is free draining but in a wet climate will retain moisture, especially in cold weather as water 'sticks' to the gravel via surface tension and some of this will be wicked to the wall. It could be ok, or not.

Personally I dont stand for this sort of stuff and I would demand they dig out the border and make the gravel level.

Alternative to wood? Anything that doesnt rot, ie masonry.

Looks like there is already a concrete edging stone fitted at the front, something like that, but there are hundreds of different pamments, pavers and edging blocks, from terra cotta, concrete, to stone.

No idea why they used wood tbh, unless they quoted a fixed price and are skimping, concrete border is only about £5 lm more than exterior grade 50x150mm joist. Sorry, these guys appear to be interested in profit and ease of work over quality of result.

 

[mardinor]

"slim ish long lasting material?"
I've used rite-edge to good effect - brown aluminium and about 5mm thick max (rolled edge). Expensive but long lasting and unobtrusive.
But tbh, given you have concrete edgers then repeating these would be far cheaper and look more uniform.

 

[Toby Newell]

"slim ish long lasting material?"
I've used rite-edge to good effect - brown aluminium and about 5mm thick max (rolled edge). Expensive but long lasting and unobtrusive.
But tbh, given you have concrete edgers then repeating these would be far cheaper and look more uniform.

Excellent idea and you wont even see it as basically buried. If you can get in small enough quantities with free delivery then not sure its that much more expensive than concrete edgers, although the edgers available everywhere.

 

[data72]

Thank you so much

 

[William]

Probably most of the angles have been covered. I would add that it cannot be correct to excavate against the wall and then refill, albeit with a free-draining medium, to a level above floor level. Anything is better than a flower bed though.

I have faced the very same issue and basically, opted for pretty much the same solution as you seem to have proposed in principle, prior to the work. I would add a couple of comments, that the lower the finished outside level, the better, so why abandon potential advantage in favour of finishing the job anywhere near, let alone above floor level. Totally agree with the other comments about wood.

Then there’s the medium with which you backfill your excavation. The more air the better so it should follow that the coarser the aggregate the better. Large pebbles look okay and are available by the ton (expensive) or even masonry, carefully placed to maximise air gaps and if necessary for aesthetic purposes, topped off with a thin layer of pea shingle, pebbles, slate chippings etc. Don’t tell anyone, but I backfilled most of my excavated trench with broken roof slates, suitable smashed, and a few broken bricks, topped off with shingle - even managed to get it so the broken slate sloped away from the wall. All worked well. I suppose there’s no reason why, if you wanted to go to town with ingenuity and effort, you couldn’t even line the back of your excavation with a wall of spaced bricks or blocks, a healthy distance from the house wall and top it off with some sturdy mesh, which could then be topped off with something nice looking.

The drainage pipes are a great idea – helps remove free water plus gets air into the bottom of the excavation so in theory at least, you can’t have free water above it. I did that too, using perforated land drain. I assume that’s the sort of thing you meant by drainage pipes.

One last comment, bear in mind that over the years, accumulated organic debris can conspire to sod up your best efforts unless you make it easy to keep clear of leaves etc.

 

[data72]

Hello William. Thank you so much. They did a new French drain but based on what I can see it has undermined my confidence in the work. They fed the French drain into the existing pipe that collected rain water from roof gutters but i will investigate how that works. My fear is that if the height and angle of the French drain into the soakaway is not well thought out , you might end up with back flow of rain water into the French drain.
Don't you just love playing building police ?...

 

[Toby Newell]

lol, I hate builders

 

[data72]

So these photos are now sheer comedy. The blind end of the French drain is left open so that it fills with gravel. The feeding end into the soakaway drain is higher than the blind end , so not a downward sloping draining angle . The perforated drain has been wrapped periodically by a fabric ( guess they didn't have enough) one hopes its non woven geotech, like a sock. This is a complete no no . It should be enveloped in gravel and then the whole thing wrapped in the fabric as the soil is silt . The whole thing sits on top of a at least 50 cm of gravel..whereas it should be at the bottom of any gravel..
The gravel should not be gravel, it should be much larger round stones as they offer better faster drainage.
We have had 2 solid days if sunshine on a south facing house but the walls of the house touching the gravel remain wet
I really should send this to Michael McEntyre..
How do I know this ? I watched 8 h of French drain specialist youtube videos by an American

What's the worst landscaping job you guys have had done by "professionals "

 

[data72]

One more question.
Is this how the French drain is supposed to feed into soakaway?

 

[Andrewnicholas]

Hello, I’m a bit late to the meeting. I have the same problem as what you’ve described. When you removed your gravel, did you leave the void empty?

I largely agree with the above. If the gravel is deep enough then it'll probably be OK, but does seem like why do it like that....
The problem with gravel as I found out, is that although it's free draining, it doesn't allow evaporation. If you scrape away the top layer, the gravel will be holding some moisture - not as much as soil, but the stones won't be dry.
Here I had to remove the gravel altogether and have free air, but I was dealing with very porous and absorbent soft red bricks. I don't know how porous and absorbent your stone would be. I think it comes down to "try it and see..." But if it were me, and that gravel went down a ways, I'd be scraping some off the top.

 

[Zebra]

I have had a gravel trench arrangement at the back of my house for about 10 years now. Over the weekend I have excavated all the gravel and left it as free air because the worms had filled all the voids in the gravel with soil, rendering it virtually useless.

(The only reason I put gravel there rather than free air in the first place was because there is a underground drain pipe in the gully, taking the rain water from the downpipes away. The gravel was to protect the pipe from UV damage.)

The gravel was a little higher than I'd like it, almost up to the DPC. When I checked on it a few weeks ago it was full of soil and some weird roots.

I'm going to leave it the pipe uncovered now. I figure that a UV damaged underground pipe is essentially sacrificial and easily replaceable.