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====== RISING DAMP ======

Georgian **buildings** were not built with a damp-proof course (dpc), and most are subject to some rising damp, which is often recognisable by a continuous band of dampness and discolouration on the ground or basement floor, or by efflorescence on the plasterwork.
Unless it is severe, rising damp is not a structural problem, though the damage to plaster and decoration may be unacceptable. There is also a risk of causing dry rot in nearby timber but with adequate ventilation this is slight.
Where rising damp does constitute a problem, there are three possible solutions:
a) insert a dpc;
b) prevent the access of water to the wall;
c) concealment.
a) Inserting a dpc

The construction — two skins of stonework with a rubble core — makes it impracticable, if not impossible, to insert a traditional felt or lead dpc into external walls in the New Town. There are proprietary methods that claim to alleviate rising damp either by chemical injection, * or by neutralising or reversing the positive potential of the wall relative to the earth using an electric charge (electro-osmosis). Neither of these methods can be recommended without reservation; it may not be possible to ensure full penetration
by chemical injection into rubble walls of composite construction containing voids, and the claims for electro-osmotic systems have yet to be proven. The third system sometimes proposed uses high capillary ceramic tubes, but this is unsuitable for drying out basement walls. While techniques are continually being developed and studied, it is wise to obtain impartial advice before specifying any one proprietary system of damp-proofing. As a traditional stone building works by absorbing moisture and then slowly drying out, surface waterproofing treatments should never be used. Waterproofing agents can never provide a permanent barrier to the passage of moisture, and only hinder the natural drying-out process. ‘To be effective, damp-proofing must be thorough and must protect all floors and walls against penetrating moisture. Damp which is prevented by a dpc from rising in basement walls will be diverted to unsealed floors or other weak points in the construction. Where basements are inhabited and are properly ventilated and heated, rising damp is rarely a serious problem.
Image sketches: 
Rainwater pipe gulley.
The shingle should be treated with weedkiller and raked over occasionally to ensure proper percolation and shingle evaporation.
French Drain: 7% hardcore and 100mm field drain aid to a fall 300mm

b) Hindering the access of moisture to the wall
Results will often be achieved by digging out earth which has been banked against a wall, and by clearing away trees and shrubs which have been planted too near the building. A ‘dry area’ along the base of the wall, formed by lowering the water table with site drainage, will assist in many cases. 
c) Hiding the visual symptoms

Concealment of damp areas is not recommended, but may occasionally be acceptable if the enclosed space is ventilated. A plasterboard lining on battens is the simplest method of concealment, but all battens must be pressure impregnated ° with a non-staining, inodorous preservative and both the wall surface and the back of the lining should be treated with fungicide. Alternatively, a barrier, such as corrugated pitch or bitumen lathing, can be fixed to the stonework and plastered over; in this case, the undercoat should be 1:1% browning plaster to clean sand, which will not shrink on drying. Re-plastering with a suitable plaster (as all specialist companies do) also hides the signs of damp (and  ailed damp-proofing systems!).
Waterproof cement, lime and sand undercoat plaster will hold back considerable penetrating and rising dampness, provided the background is well wetted before the plaster is applied, so that it achieves good adhesion. Any normal finishing plaster can be used on top of the undercoat, with the exception of pre-mixed lightweight plasters, which are not designed for this type of background.
Once rising damp is eradicated and the internal wall surface is dry, it should be re-plastered in light weight ‘renovating’ plaster to a height of 300 mm above the level of the old damp-affected plaster. If possible, re-plastering should be postponed for up to six months before renewal, to allow all the harmful soluble salts to be absorbed by the old plaster.
EXTRANEOUS CAUSES OF DAMP

These are likely to be due to plumbing leaks, faulty radiator valves, washing machine floods, etc. ‘7 The consequences can be just as severe as with other sources of dampness and dry rot is just as likely to occur if the faults are not remedied.
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