| There are essentially two ways of introducing a new | | | | insert the damp-proof membrane, the next step is to |
| damp-proof course into an existing wall, but only one | | | | clear the course on both sides of the wall. Remove |
| of these methods - inserting a new physical | | | | any obstructions such as skirting boards, electrical |
| membrane DPC into the wall is certain to cure rising | | | | connections or pipes. Then cut through the entire |
| damp in all circumstances. This is often referred to as | | | | thickness of the mortar course using an angle grinder |
| the traditional method. If a new physical membrane is | | | | or a tungsten-carbide tipped chainsaw specially |
| installed properly, there is no way that moisture can | | | | designed for the purpose. Insert the damp-proof |
| penetrate across it. The other method is to inject a | | | | membrane - copper sheet, bituminous felt or thick |
| chemical barrier into the wall. | | | | polythene - and drive wedges into the gap between |
| Putting in a physical barrier | | | | the brickwork and the membrane until this gap can |
| Any physical membrane introduced into the wall will | | | | be back-filled with mortar. Do not tackle any more |
| have to be let into a course of mortar. So, the first | | | | than half to one metre of wall at a time to prevent |
| problem is deciding which mortar course to use. In | | | | settlement and structural damage as the thickness of |
| older houses suffering from rising damp which have | | | | the mortar course is removed. Separate lengths of |
| suspended wooden floors, the new DPC should | | | | the membrane material should be overlapped. |
| always be installed below floor level and at least | | | | The equipment needed for inserting a physical |
| 150mm above outside ground level. The DPC should | | | | membrane can usually be hired from a tool-hire firm, |
| be inserted below the level of any wooden wallplates | | | | but you should take great care when using it - large |
| or joists which are in direct contact with the outside | | | | angle grinders and chainsaws are potentially |
| walls. If the structure of the house makes this | | | | dangerous tools and there is always the possibility of |
| impossible, apply liberal quantities of wood | | | | cutting through electrical cables or gas or water pipes |
| preservative where necessary. Apply wood | | | | you did not know about. |
| preservatives as well to any timbers which have | | | | There are many firms who specialise in this sort of |
| become damp. | | | | installation, and it may be wiser to call one in rather |
| In houses with solid floors which have a damp-proof | | | | than to attempt the job yourself. The technique |
| floor membrane, the DPC should be inserted as near | | | | does have its limitations and is the most expensive. It |
| to the top level of the floor as possible, and any | | | | cannot be used on very thick walls or on walls with a |
| remaining gap on the inside wall should be painted | | | | loose rubble infill. It can be used only on walls with |
| with a bituminous-type material. This will protect any | | | | regular mortar courses such as brickwork or coursed |
| wooden skirting boards placed over the gap which | | | | stone blockwork not on the random coursed flint |
| are in direct contact with the wall. | | | | walls that are found in various parts of the country. |
| Once you have chosen the mortar course in which to | | | | |