Using broken terracotta roof tiles for drainage - good idea or not?

CelticRambler

Can I kill two birds with this one stone?

Problem number one: the atrocious weather of last year removed a considerable amount of my south-facing "historic" barn roof (100-ish year old terracotta tiles) and the now-exposed north facing part has been/continues to be progressively dismantled by wind and rain. As a result, I have about 20 cubic metres of smashed tile to deal with.

Problem number two: the same weather exaggerated a known issue with an occasionally too-high water-table, which I'm hoping to manage with a simple drain cut across the natural flow of water within the soil. After last weekend's rain a "proof-of-concept" trench dug a couple of weeks ago is full to overflowing, so I think it's in the right place and will limit the amount of seepage into the farmyard.

For various reasons (particularly mosquito control) I'd prefer this drain to be backfilled. Can I just dump all the smashed tiles into the trench and expect it to keep working as a drain for many years to come, or do I need to do more with the tiles first? They'll need to cleared and shifted by hand ( … yeah … ) so I can do a bit of sort-out as I go, if there's an ideal size/shape for this kind of job.

148multi

Would not use them for drainage, think round stone.

standardg60

You can use the tiles no problem but unless your trench directs the water into a drain or ditch filling it will simply force the water back out and you'll be back to square one.

A trench on it's own is pointless because while it will hold more water, as you've discovered once it fills it ceases to be of any further use. This is why soakaways don't work in the long run.

T-Maxx

Soakaways when properly designed, soak away.

standardg60

https://www.boards.ie/discussion/comment/123386721#Comment_123386721

Could you elaborate on the ways and means of that assertion?

T-Maxx

Essentially the size of the soakaway is determined by the in-situ infiltration rate and the volume of runoff.

standardg60

https://www.boards.ie/discussion/comment/123386919#Comment_123386919

And that is established by how long of a test?

T-Maxx

As long as it takes for the water to drain away out of the hole.

CelticRambler

https://www.boards.ie/discussion/comment/123386142#Comment_123386142

It's only a trench (rather than a drain) at this stage because I need to keep the farmyard access undisturbed for the time being; in due course, it will empty into a tank and be pumped to where it'll be more useful.

Having said that, the overflow is already making its own way to where the tank will eventually be located.

There's absolutely no question of creating a soak-away - standing water on my soil doesn't soak away (hence the mosquito problem) - but that side of things is already being dealt with.

What I'm asking is whether or not the smashed tiles would be a suitable filling for the drain, prior to it being covered with a layer of topsoil. And if the answer's "well, maybe …" then what might I need to do to/with them for best effect?

minerleague

By terracotta you mean clay fired? ( not concrete based) If so will they revert back to clay over time when immersed in water and soil? As you have them for no cost suppose its worth chancing them

standardg60

https://www.boards.ie/discussion/comment/123387012#Comment_123387012

Ah ok I think we're talking about two different things. You're determining via a percolation test whether an area is suitable to be used as a soakaway, whereas what I mean is a soakaway in an area of poor drainage won't soakaway any better.

CelticRambler

Yes, probably clay fired. Some of them would be getting on for 2-300 years old at this stage. Given the amount I've found during excavations from a previous change-of-roof, I'm pretty sure they'll last at least until the end of my retirement!

Would there be any advantage to layering them in, say a layer of the flatter ones (i.e. three quarters intact) at the bottom, then the well-smashed bits, then another layer of flat ones? My thinking was that that'd limit the amount of soil dropping down, clogging up the spaces.

For info, the neighbouring industrial-scale farmer did a "proper" job with his adjacent field, including laying who-knows-how-many km of agricultural drain. That field is still as wet as ever, to the point where he can't get a tractor in for several months of the year.

minerleague

https://www.boards.ie/discussion/comment/123387866#Comment_123387866

If it's only a small trench would it be worthwhile lining the sides with some geotextile fabric? Wouldn't bother being too exact with putting them in tbh just fill close to top

yosemitesam1

https://www.boards.ie/discussion/comment/123387866#Comment_123387866

Are you on very heavy clay soils?

standardg60

https://www.boards.ie/discussion/comment/123387866#Comment_123387866

You want to maintain as many gaps as possible in the trench when filling it to allow the water to flow in and along it. There are 'soakaway crates' now specifically for this purpose.

My thinking would be to lay the bigger tiles flat but with gaps between them to create tunnels and then overlap with the next layer and so on.

10-10-20

Fired clay is ceramic. A lot of the fields of Ireland have field drains lined with clay bricks in an n shape, and many of them are a hundred years old.

CelticRambler

https://www.boards.ie/discussion/comment/123387993#Comment_123387993

Desperately heavy! When shifting the subsoil, I can tip the trailer to 135° and the stuff still won't fall out … but neither will it support the weight of any vehicle bigger than a barrow once it's saturated.

https://www.boards.ie/discussion/comment/123387921#Comment_123387921

I did consider that, but I think the suspended clay would clog it up in no time. Plus it's a cost that's not really justified. The total length of the various drains for this scheme will be about 150m, of which about 70m will skirt the farmyard directly. I'll keep my funds for that part of the project.

yosemitesam1

https://www.boards.ie/discussion/comment/123389353#Comment_123389353

It's hardly dept 32 or 47 you're in?

If so, I wouldn't be covering the drain with any soil. Fill it with gravel or tiles. I don't think it'll matter too much

CelticRambler

Nah, 36. It has to be covered - our traditional mosquito problem has been getting steadily worse, and now we have tiger mosquitos as well, so every puddle and other square centimetre of stagnant water has to be go rid of.

Looked at barn to convert in 47, back in the day, but decided it was far too hot. A very good decision in retrospect. We've also been spared the flooding that's affected so many other parts of the country over the last couple of years, including this week.

10-10-20

https://www.boards.ie/discussion/comment/123390176#Comment_123390176

Out of curiosity, what seasons are they now active in and how has that changed in the last 20 years? As a visitor to Sarthe and other regions West of you, I noticed a significant change from ~2005 onward - June was rainy-season, effectively!

Your broken tiles would be fine to add around a formed channel such as a plastic land-drain or the brick construct which I described. But it might be advisable to talk with people locally to see what they have found to be the most effective method for the 'terroir' as geotextile (or the like) might just clog up in a matter of months.

yosemitesam1

https://www.boards.ie/discussion/comment/123390176#Comment_123390176

All depends on the soil really. Don't know what it's like there. But if it's covered over with heavy clay, it will reduce the effectiveness massively

Jb1989

Where does it say what country your in. What's all this dept stuff yous are on about. I'm lost

CelticRambler

https://www.boards.ie/discussion/comment/123391240#Comment_123391240

Turn on your GPS! :D

Back in the day, before the Great Upgrade, the profile info on the left used to include the member's location (if given). The other posters either have long memories, or might have seen in other threads that I live in France.

https://www.boards.ie/discussion/comment/123390301#Comment_123390301

They're almost a year-round nuisance these days, but it depends very much on how wet the spring and early summers are. I was still getting them in the house up to the end of January this year, and had one whistling in my ear a couple of weeks ago. Was working away all of Feb and March so don't know what the story was then.

I moved here in 2004, at which time we used to have four proper seasons, with a decent amount of snow during the winter every year until about ten years ago. That year of the big freeze in Ireland (ye were far colder than we were here) was the last cold winter we've had. Most summers since then, on the other hand, have been blisteringly hot with moderate or severe drought. That's generally great for keeping the mossies out of circulation as the ground is bone dry. But it started raining in autumn 2023 and didn't stop till Christmas 2024, so we've had lots of (standing) water and warm/hot temperatures that allow the mossies to breed all year round.

Sarthe's status regarding the Tiger Mosquito (and a few other départements in that corner) was upgraded from yellow to orange at the start of last year.

Calahonda52

CR, do you plan to put a perforated land drain pipe in the bottom or at 150 m maybe too expensive.

I would consider one and then fill, starting with the larger pieces and then grading down to smaller pieces as you get up to surface.

If driving heavy kit perpendicular over it maybe a slug of concrete with some rebar..

Keep well

CelticRambler

Based on the farmer neighbour's experience with perforated drain, no - I'm convinced that'd be a complete waste of money. He runs a "public works" company and had those lads in to do the job, for no significant gain (they willingly accepted my suggestion to drop a load of felled trees on my land last year because they couldn't haul them across the field to their usual dump site …)

The traditional technique in the area is to dig a big hole, then a series of ditches running into it (our local tourist area is nicknamed "land of the thousand lakes") Unfortunately for me, my house, barns and yards are at the lowest point of the property, and the historic drainage just diverted everything off to the local stream. Because of the recurrent droughts, I'm trying to keep that water on/in my own land.

At this stage, if no-one can say it's a bad idea, I think I'll make a pilot project out of this trench and see how it goes. The priority at the moment is, in fact, to "creatively" dispose of the tiles rather than sort out the drainage, so that I can get back into the roof-less barn.

10-10-20

https://www.boards.ie/discussion/comment/123393496#Comment_123393496

Not sure I follow on the point around wanting to keep the water on your own land, yet also need to reduce exposed water surfaces as they appear to contradict. How do you intend on keeping the water, sumps?

How thick is the clay layer and what are the sub layers made up of, and do they provide drainage?

yosemitesam1

https://www.boards.ie/discussion/comment/123393496#Comment_123393496

You're biggest issue from the drainage pov is getting water into the drain. Percolation through the soil will be minimal unless you have some free draining soil near the surface

10-10-20

https://www.boards.ie/discussion/comment/123393646#Comment_123393646

Exactly, that's why I was suggesting to look locally to see if they had a local/regional approach to the issue, but it appears not. Maybe there are documented solutions from other clay-type areas, parts of the South of England also has heavy clay types, I'd be sure that much of how to drain land has been documented online.

yosemitesam1

https://www.boards.ie/discussion/comment/123393686#Comment_123393686

If it's the similar soil to what I've seen further south. It's a case of open drains or else fill to the surface with gravel or sand or the broken tiles. An inch of that heavy clay on top and it will flow straight over it and continue the down the hill

CelticRambler

Sorry for the delayed follow-up - have been playing in the dirt while the weather's fine. :D

A quick point of info regarding some of the comments above : my "broken tiles" query is just one small aspect of a long, long-term management of the water flowing on/through my parcel of land. I've spent twenty years getting to know every hump and hollow, and figuring out where the wetness is and where it wants to go. It's no accident that the trench I dug a couple of weeks ago filled up as it did : I was looking for a "spring" that I knew had to be there somewhere. Okay, a sorry excuse for a spring - more of an incontinent dribble - but enough to cause trouble if left to do its own thing.

Anyhow :

https://www.boards.ie/discussion/comment/123393621#Comment_123393621

The paradox is that our default summer state is one of drought and a near-total ban on using water for anything other than keeping children and animals alive, and watering "family" vegetable plots during the hours of darkness (no derogation for farmers). We've had such bans last for seven or eight months at a time (2022, 2023) so I'm aiming to store about 10,000 litres over the winter to be used during future droughts. These periods are not problematic for mosquitos, as the ground is bone dry; but in autumn, winter and spring, they will breed in even the smallest puddles.

How thick is the clay layer and what are the sub layers made up of, and do they provide drainage?

The layer of topsoil varies from 5 to 25cm, which sits on a subsoil of clay-clay, as in the kind you make pots out of (the children used to dig it out of the neighbour's ditches for that very reason). The topsoil is clay-rich and soaks up water until it becomes an unworkable gooey mess, at which point any surplus water flows downwards to the subsoil, and then sideways along the top of the subsoil until it escapes somewhere, e.g. where someone's dug a hole!

This is a fairly typical cross-section, from the high part of the new trench. Probably not too easy to see in the picture, but the topsoil there is "very damp" but not wet; but there's a steady flow of water from the base washing the cut surface of the subsoil (at the 25cm mark) and collecting at the bottom of the trench.

So getting water into a drain isn't a concern; the problem is keeping it flowing in the required direction. As I mentioned before, it looks like the proper perforated plastic drains installed in the field across the lane were very quickly clogged up. Having watched the seepage from the "spring" over this last week, and done lots of thinking, I'm going to fill the drain almost to the top with the well-smashed tiles, put a flat "roof" of bigger pieces over the top, then cover the whole thing with about 10cm of topsoil.