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Welcome to the Damp section : Dealing with damp in older houses
How to inject a damp-proof course (DPC)

Here we show how to inject a new damp-proof course into an old brick wall. If you are looking to inject a new DPC into an entire house (as we've done here), it can be a big job, but there are no specialist skills required, so basically its the sort of job most keen DIY folks should be able tackle.

The specialist equipment for injecting the damp-proof fluid is available at most tool hire shops and its easy to use.

I suppose the biggest hurdle for most is that the job does involve a fair amount of disruption. For instance rooms will need to be cleared, skirting boards removed, hundreds or thousands of holes will need to be drilled into the brickwork (or mortar depending on the method chosen), and in some cases if the plaster is damaged it will need to be replaced up to the height of about 1 meter (3 foot).


Before you start, choose a method. The two most common methods of injecting a DPC are a) injecting into the brick or b) injecting into the mortar layer.


The most common method is to drill holes into the brickwork and inject a special waterproofing fluid directly into the brick at high pressure, but this method is quickly being replaced by a relatively new process where by a water-proofing cream is injected at low pressure into the mortar layer by using a type of calking gun. The 'injecting into the mortar layer' method is often preferred by conservation authorities as it leaves the brickwork intact.




    Rising damp in floors: old 'eart
    To fix the pro.
    2. Penetraing Damp
    Penetrating Damp: this is where water is entering into the house as a result of a 'physical' problem, such as a damaged or blocked guttering & downpipes, roof tiles missing, roof flashing damaged, rotted window sills, porous mortar (brickwork may need repointing) etc.
    Penetrating damp is usually easy to identify since it is shown as damp patches in walls or ceilings, which become more noticeable when it rains. Its recommended you fix the problem quickly since penetrating damp can damage plaster, rot structural timber, interfere with electrics and so on.
    To fix the problem: identify where the water is coming in and investigate the exterior of the house. You should be able to identify what the cause is and what is in need of repair.
    3. Condensation
    Condensation: Old houses were drafty. They were built with open chimneys, single pane sash windows, and no insulation. This resulted in a constant supply of fresh air circulating through the house, allowing it to 'breathe' and release trapped moisture.
    Over the years most of theses houses have now been fitted with double-glazed windows, draft-free doors, high performance roof insulation, and had those lovely drafty chimneys blocked off.
    As a result of the restricted airflow and ventilation, it's not uncommon to find condensation problem in older houses. To rectify the problems increase ventilation and ensure insulation is properly installed.
    To fix the problem:
    Walls: ensure air bricks and vents are clear (you may need to add an airbrick). Install an extractor fan in your bathroom/shower room. You may decide to insulate solid brick walls (see our feature click here…)
    Roof: ensure loft insulation is not blocking airflow from eaves
    Pipe work: if pipes are sweating add pipe insulation (pipe lagging)
    Windows: if modern windows are fitted ensure they have a trickle vent.
All of the DPC (dampproof course) injection equipment and specialist fluid should be available to hire from most tool hire shops.

Minimal skill level is required but working at floor level for prolonged times can be tough on the old knees & back!

The injection equipment is simple to use, but the actual injection process is so repetitive I've found my mind wanders every time I've done this I've wound up spraying myself and the room with the injection fluid stuff. Luckily the fluid used today is water-based and not as nasty as the stuff used a few years back.


  © 2006