Ground Penetrating Radar Survey
By: admin | Posted on: September 18, 2021
Ground penetrating radar survey, is also called a gpr survey.
What can ground penetrating radar detect?
Can ground penetrating radar detect an old covered over basement / cellar?
Can ground penetrating radar detect leaks in mains water pipes?
Can ground penetrating radar detect a covered well?
Ground penetrating radar has the potential to find all of the above, subject to the limitations of the GPR equipment being used, and the ground conditions at the time of survey.
I have really only purchased this equipment to really help with solving complex rising damp issues. This equipment will give me the opportunity to go further with the investigation, and identify any other potential causes. We all know rising damp issues are caused by excess moisture, and this moisture could be coming from the ground via defective and damaged leaking wells, poorly installed French drains, blocked up old culverts, blocked up old land drains, and general drain issues.
In 1868 the bye-law of the Wiltshire Warminster local board, was the first one to deal with damp, before a physical damp proof course became part of the bye-laws (see below).
Drainage of sub soil and prevention of damp. Warminster Byelaw 1868
The house drainage shall be so constructed either with additional earthenware pipe drains or otherwise, as to drain the subsoil of the premises, whenever the dampness of the site appears to the Board to render this necessary; and all rainwater shall be so drained or conveyed from the roofs buildings as to prevent it’s dripping onto the ground and causing dampness in the walls.
What I did notice though, in the drainage section all drain pipes had to be laid with watertight joints, and beneath houses they shall be imbedded in and surrounded with well puddled clay… no mention of this with the subsoil drainage though.
As you can imagine these land drains would be possibly blocked up by now, and might even be damaged, causing ponding water to that area, and possibly subsequent damp issues within the property. The ones I have found previously was just simply by luck!
I’ve done some videos that will certainly make you think how valuable this is, in regards to damp surveys…..look at the well in the image that was covered over, knowbody knew it was there.
Extract below about land drains, and drainage from an old book in regards to damp issues. Ive noted on all references to the hidden land drains, that there is always a slightly different specification to install… but they all talk about them blocking up, and potentially causing problems.
The greatest difficulty with which an architect has to contend with in the ground-works of a building is that of the ground water in low-lying lands. Springs on hill-sides are easily dealt with, but the water which percolates through mud and gravel only a few feet below the surface of the ground, and rises and falls perhaps with rise and fall of a neighbouring river or ditch, furnishes a more difficult problem. Nor is a site like this confined to plains; it may be found on the banks of rivers, even in deep narrow valleys.
A permanently high level of ground level of ground water is dangerous of health, but fluctuating ground water is much worse. It is one advantage of subsoil drainage that it tends to prevent extreme rise of the water, and so lessen the degree of fluctuation.
The level of ground water, it may be added, is always raised by capillarity. The amount of rise has been estimated at about 1 foot in sands, and 4 or 5 feet in clay and compact marl. The rise will be lessened in many soils by properly opening them and draining them.
In many cases, it is a mere farce to talk of draining subsoil to a depth of 6, 8 10, or 12 feet; not until the ocean has been drained, can the level of ground water in many parts of these islands be permanently lowered. Where the sea has to be kept out by dikes and sluice-gates, it is of little use talking about subsoil drainage. So difficult is to to render dwellings on such low lying sites habitable, that by the London Borough Act 1894, the London County of dwelling house upon them. In many elevated places, however, there are even damp and boggy, patches of ground, and these can easily be drained, because there is an outfall for the drain into the valleys below.
The essential fact to note is that subsoil drainage can only be carried out if there is a lower soil to drain to. In the absence of this the site must be raised if necessary.
Not all ground requires under drains : many rocky, sandy, and gravelly sites are sufficiently dry already. But every site must be judged by itself, as the nature of the ground varies greatly even in a short distance. It is better, however, to drain too much than too little. The drainage of clay soils renders them drier, and, by reducing the evaporation, warmer. Sand and gravelly soils are naturally drier and warmer than clay; on account of their porosity of water rapidly sinks through them, and they contain a considerable volume of air. In these the fluctuation of ground water and consequent exhalation of more or less impure ground air are more to be feared than dampness.
Sub-soil drains are sometimes merely trenches cut to the necessary depth, and filled to the height od=f 2 or 3 feet with broken stone or chalk lumps. The ground water finds its way along these “rubble drains” (for so they are called) to the appointed outlet. Sometimes a small square drain is formed at the bottom of the trench of stones, or with tile bottom and brick sides and top. Pipes, however, permit the water to flow off more rapidly ad are less liable to choke than stones drains. They may be either round or D –shaped. And should not be less than 3 inches in diameter. Unsocketed agricultural drain pipes are often used, but there is some difficulty in keeping the ends of the pipes together, both horizontally and vertically. To obviate this , half collars 3 or 4 inches long are sometimes placed under the joints, or pipes with a socket on the lower half only are used. Ordinary socketed drain pipes are also used, but with the joints left without cement or clay. The last two methods are the best. Whatever kind of pipe is used, the trench above should be filled with broken stone or screened gravel to the height of 1 or 2 feet.
In very wet and loose sandy soils, drains may carry away, little by little, considerable volumes of sand, and so endanger the ground and structures above. In extreme cases of this kind, sub-soil drains will be best omitted, and the money thus saved expended on a concrete bed over the site covered with a layer of asphalt. The depth of the sub soil drains should be as great as possible, but considerations of outfall and expense will frequently prevent the depth being more tha 2 or 3 feet below the lowest floor. Where the drains are shallow, they should be close together than is necessary when they are deep.
The distance apart of sub-soil drains must depend on upon their depth, the quantity of water and the nature of the ground. A common rule for the distance apart is two or three time s the depth. The stiffer the ground, the close they must be . In stiff clay they should be laid every3 or 4 yards, in loamy clay every 5 or 6 yards, while in sand and gravel they may be omitted altogether, or at the most a single drain may be laid around the outside of the building. In the other cases, however, it will usually be necessary to lay branch drains across the site in addition to the important drain encircling it.
Any walls crossing over a rubble drain should have a rough arch formed above the footings, so as to carry the main weight clear of the disturbed ground.
The outlet for ground water must be arranged according to circumstances. In many towns now, special “sewers” for surface water and ground water are provided, emptying into the nearest stream at various convenient points. In the country the sub-soil drains may be carried to the nearest stream or ditch, or, if there is sufficient fall, brought to the surface of the ground at some distance from the house. Where, however, they must be connected with the sewage conduits, they must be trapped from the house drain as well as from the public sewer.
The best method is to build an inspection chamber by the side of one of the inspection chambers on the sewage drain, and to build the trap into the wall between the two, but well above the sewage drain, so that sewage cannot pass into the trap. There is one obvious dis-advantage in the connection of the sub-soil drains to the sewerage-drains, and that is that in dry weather the water in the trap my evaporate, and more or less foul air from the sewage –drains may then pass along the subsoil drains, and find its way into the house. The risk is reduced by connecting some of the rain-water to the inspection chamber in which the trap is placed, but at the best the connection of the sub-soil drains to the sewage cannot be recommended. On flat low lying sites, it is better to raise the house or terrace, and to drain the ground to as great a depth as possible by means of open ditches, into the water-drains from the house can be laid to discharge.
If you have a damp issue I have the necessary equipment, along with the experience to find out what is the root cause, by eliminating any potential causes.
How much is a ground penetrating radar survey?
Survey costs can vary depending on what is needed. Mine is mainly used to help solve damp issues, where excess water can be causing rising damp issues or flooding within a property. This is normally used as add on, as part of a damp investigation.
If you have any queries, and need have a problem, you can email me enquiries@completepreservation.co.uk