Ground Penetrating Radar

What you need is drain rods poked in from the nearest ispection chamber.

What inspection chamber would that be harry?

"some *disconnected* clay/plastic pipe-work"...

No experience, but I had a look at the Wikipedia article. The photo of the output looks fairly easy to understand.

What type of soil do you have?

Yes, exactly!

Gravel and clay.

I note that the resolution is affected by how wet the soil is, but I think I understand (just) enough to be aware of the affect of the frequency settings (higher = shallower, lower = deeper).

And, no doubt, you read "In moist and/or clay-laden soils and materials with high electrical conductivity, penetration may be as little as a few centimetres."

Before you splash out a couple of hundred quid on equipment hire and several hours on a steep learning curve, you could always have a go at this

All you've got to lose is a couple of bent coathangers and the respect of your friends and family[1]

Nick [1]And if successful gain huge respect from friends, family, neighbours, local press etc etc.

I've used a couple for a short time, simple they are not.

The first thing is that the specifications are about as accurate as an

Secondly the image produced requires a lot of interpretation, you are often trying to pick up small indistinct patterns in noise. If the pipes are empty they may show up well, if clay and filled with similar material to their surroundings they won't show at all or very indistinctly.

Thirdly, GPR comes in varying frequencies - lower (300MHz) give better penetration but poor resolution. These are typically used for archaeology. Higher frequencies (1500MHz) give better resolution but much worse penetration, about 500mm in good conditions. 900MHz is often used for pipe detection and has a range of about 1m.

Depending upon how large an area you want to survey you might find it more cost effective to hire the device plus an experienced operator.

... a lot of wasted effort digging up the wrong area of concrete?

Thanks for your input.

May I ask, what do you define as a short time?

With a week's rental, I figure I could spend the first couple of days on known-knowns, and gradually expand over the week.

Any idea what kind of costs this would be? I'm stuck in "phone-for-quote" land for these services and they all seem geared towards large projects and I'm interested in a patio.

Just out of interest, if these drains are disconnected, why do you want to find them?

Tim

About 2 days a week spread over a month.(The man who really understood it could only be on site 3 days a week so I played with it when he wasn't there). We were looking for some 1 inch lead water pipe about

No idea I'm afraid. It was a year ago, the machine and operator were not paid for by us and it isn't something I've needed to use before or since.

I'm not sure what you're getting at without a clearer picture and not having to make presumptions.

Most disused pipes should be scrapped from being of an unknown provenance. Best to start from scratch.

He said he was looking for them, not that he wanted to reusee them

Well... thanks for being interested Tim, this may be too much detail, but here goes:

We have had an on-going problem with rats getting into our roof structure, and I'm trying to eliminate any possible source of ingress.

We've been through several rounds of bait-and-kill, and have a blimey load of surveillance (cctv), traps and poison, in the roof (think "Hunger Games"). Activity dropped to zero about five weeks ago, but a couple of days ago I noticed we had a new visitor.

Being aware of the need to eliminate all access points, the roof itself has been inspected (several times) and various potential access points closed/filled. I've had all the existing drains surveyed, mapped and proofed where required. There are (now) no climbing plants on the walls etc.

The local pest control guy (who I rate) has inspected the property several times and we're both baffled about how they're getting in.

The house is a big(ish) bungalow in a semi-rural environment. I contacted the local council and got copies of all the relevant planning permissions and it turned out that an extension was added in 1963 and it is this part that included the flue that you and others kindly identified in the "Chimney Pot Identification" thread.

After talking with neighbours, it was suggested that the extension was originally used for commercial food preparation/cooking.

The conundrum is that there is no clear route to the current drainage from the extension. (The two down pipes in the Chimney thread simply evacuate onto a gravel bed).

In addition to the extension, in 1963 an adjacent plot was used by the same developer to construct another bungalow.

Now, my suspicion is that the developer connected the extension drainage to the adjacent bungalow (it may have been easier).

Subsequently, a later developer (~1980s and for which there is no planning permission), capped off one of the 4" pipes in the existing drainage system. We found this during our initial drainage survey, and it looks like a bodge-job. It allowed access into the floor void and the cavity wall from the mains drainage network. So we capped this properly about 18 months ago.

But clearly, it didn't fix the problem.

Maybe 1980s developer did the same/similar thing for the drainage in the extension, and that's my current line of inquiry.

i.e. drains in extension connected to neighbours drains, subsequently capped in a manner which allowed access to the extension cavity wall or even the floor void. (The floor area in the extension is now a mix of concrete and suspended - but concrete where the drains may have been).

And so my desire to understand what may be going on under the house. I figure that with a week's worth of rental, I can use GPR internally and externally to build a map of what is under the extension.

Naturally, of course, I've had discussions with my neighbour about their drainage, but short of me paying to have their drains surveyed (and/or scaring a little old lady about having rats in their drains), some non-destructive GPR strikes me as the best course of action.

A long story, and not finished yet. There is still digging yet to do!

Regards

WeeBob

I've no idea how they are getting to the roof but don't discount the possibiity of them starting their journey through disused drains.

The organisation I work for used to own a repurposed main post office building. During the early 20thC latrines for the posties were installed in the undercroft and these were all but forgotten about in modern times..

...until rats started getting into the building. They had crawled their way down the disused waste pipes from outside. How they got into the building from the undercroft I have no idea (cf with the OP's roof) but pouring cement into each and every WC and basin stopped the problem.

Nick

In message , Phil L writes

Concur on the drains but differ on the insulation.

We have had issues with mice particularly Woodmice. The problem started with them moving a quantity of Walnuts from the garage to the loft over our bedroom (about 25m).

The route appeared to be through the open cavity at the garage door where it joined a timber barn. Through the cavity Rockwool insulation to the soffit. Along the soffit to the main house then through/over the insulation in the hall raised tie ceiling. This gave access to the house attic where they proceeded to eat the Walnuts very noisily.

There were mice in the chalet bungalow loft I am extending. Again, up the cavity through the insulation. Point of entry was probably where the kitchen sink waste penetrated the brick exterior wall.

Maybe try another approach: track the rodents. UV-shiny dust is used, and UV flashlights are plentiful on the bay, and net.

Yellow-tinted glasses make the fluorescence easier to see, an

First hit for a search for "fluorescent track rats"

Thomas Prufer