Installing Damp Proof Course

I have been trying to complete as much of the renovation work on our 1882 Victorian property myself as possible. I have recently been working on installing a damp proof course using Damp Expert injection cream from (0800 169 1106) that is easily applied with the type of ‘cartridge gun‘ that you would use for filler or mastic. Installing a damp proof course is normally a job for a professional or at very least a competent DIYer. However as you may know from previous posts, I am neither, or at least I wasn’t until recently and so the prospect of installing a damp proof course myself was causing me to experience some anxiety.

Jan 30, 2013 - The purpose of the outer skin of a building is to keep moisture out of the house structure. A damp proof course, in the brick veneer example. A defective damp proof course is a major cause of rising damp, so make sure yours are in good condition. Plumbing Any small drops from plumbing could result in a big and intense wet spot and even though the escaping water might be small, it is usually consistent and concentrated in the same location.

Anxiety that was however put to the back of my mind once I had some quotes from professional installers for the job. It’s partly for financial reasons that over the past twelve months since buying our house I have forced myself to tackle many DIY projects that I never expected to be doing myself. The results have been surprisingly good and I think I have made only a few mistakes.

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So if you’re reading this and thinking of installing your own damp proof course, I’d say be cautious but do try it for yourself. A word of warning however if you install your own damp proof course you will not have a guarantee covering the installation. In the absence of this recognised long-term guarantee that you would be offered by a professional installer your work may not be accepted by a future purchaser of the property or mortgage lender. Having said this of course in my personal experience I bought this house without a damp proof course.

If you still have your mind set on doing your own work the best advice that I can give to a novice DIYer is: take your time, research the best way to do things, plan carefully, don’t rush into anything and use common sense. This will be good advice for anyone intending to install their own damp proof course. It took me a lot longer than I thought. My philosophy so far has been, from anecdotal evidence from friends and colleagues in the industry, is that should you be unlucky enough to contract a disreputable tradesmen that they will often attempt to cut corners when carrying out repair works. This is evidenced by the previous repairs and works that have been done to the house whilst previous owners have lived here. A lot of work has been done badly, or unsympathetically to a Victorian building. A chemical damp proof course is a case in point.

Chemicals are not considered by many to be sympathetic to Victorian buildings so I was drawn to using Damp Expert injection cream because it is low hazard, non-caustic and non-flammable and also importantly it does not need to be injected under pressure. It is also a solvent-free formulation that does not contain white spirit or iso-paraffins. This was especially important to me from an ecological point of view.

I’ve filmed each section of the project from removing the old plaster and repairing the mortar joints right through to drilling the holes and injecting the damp proof cream. Each of the seven stages of the project is available to watch here on You Tube. I understand that not many people chose to take on a damp proof course installation as a DIY project as it is believed to be too complex. But I’m hoping to dispel that myth and let other DIYers know that it can be done! Naturally getting some professional advice before undertaking such a project is advisable. I spoke at some length with Damp Expert’s highly qualified advisor David Prince. There are also videos on YouTube and of course I have also made my own videos.

Hopefully one, or a combination of these avenues for advice, will help you to complete this job yourself without too much difficulty or anxiety. The house was built before any sort of chemical damp proof course techniques would have existed. The best you’re going to get on a Victorian house in it’s original state is a slate damp proof course. This is, in effect, a line of slate placed into the mortar line at a height of approximately 150mm above ground level. This slate would have, to some extent, retarded the capillary action of dampness rising up the external walls. However this isn’t exactly high tech these days and has long since been replaced by damp proofing creams and solutions.

One of the major issues surrounding dampness in Victorian houses is that they were built with suspended timber floors which require adequate ventilation to prevent condensation forming in the sub floor void which could eventually lead to rot in the timbers of the floor or joists. This means that each room needs a ventilation grille or air brick in the outside wall which allows air to circulate under the flooring to keep the timber aerated and dry. This grille or air brick should not be blocked by outside ground levels or vegetation. Once it is clear of any soil, vegetation or debris you may wish to consider digging a small trench around the outside of your house and filling it with gravel to aid the seeping of rainwater into the ground. This is known as a French drain and you will often see them around Victorian houses.

As a DIYer look out for these things when walking past houses similar to your own and you will no doubt learn a lot! A well maintained French drain will also make sure that your damp proof course is not ‘bridged’ by the soil level on the outside of the house.

You will often see houses where the ground level around the base of the house is above the damp proof course or in some cases even covering the air bricks. This is a worse case scenario because If the soil level outside (or even inside under the floorboards) is higher than the damp proof course then dampness can ‘bridge‘ or jump over the damp proof course, rendering it useless. If fixing any air grilles or bricks doesn’t cure the dampness, or you simply want to be doubly sure you may wish to consider installing a damp proof course. Here is a step by step guide to how I installed a new cream injection damp proof course into my house:.

Remove vegetation, debris and soil from around the walls of the house that may affect the effectiveness of the air bricks and replaced broken air bricks. Remove all the affected plaster and skirting boards from walls. Repoint any mortar that needs repairing with lime mortar using a mix of 3 sand: 1 lime, although there are various ratios that you might be advised of or want to experiment with yourself. I got this ‘mix’ from the, which is reportedly the ‘traditional mix’. Replacing any damaged mortar is important to this job because if the mortar is worn out or there are gaps in the mortar line then the damp proof injection cream will not penetrate the mortar and travel along it to form an effective horizontal barrier against damp.

Drill holes in the mortar line. Building Regulations require a damp proof course to be a minimum of 150mm above external ground level. The damp proof course should also protect timber floor constructions and should therefore be positioned lower than timbers in contact with masonry.

Where these requirements cannot both be met professional advice should be sought. Holes should be drilled with a 12mm diameter drill bit at intervals of approximately 100mm and certainly no more than 120mm apart. Novice DIYers would be best advised to install a damp proof course on both the inside and the outside of a wall. In the example of my own house the walls are solid with no internal cavity and are around 200mm-250mm thick.

Damp Expert injection cream is applied with a simple to use ‘cartridge gun‘. Inject the cream into the holes using the applicator ‘gun’ to a depth of approximately 100mm-125mm per side, back filling the hole with the cream. Make sure to wear appropriate gloves (such as Nitrile gloves) which can be bought cheaply from places like Toolstation or Screwfix, just to keep the cream from getting onto your skin. Although when I did get some on my skin it didn’t seem to do any harm!. The cream will diffuse along the mortar line before curing to form a water repellent resin which acts as a barrier to stop damp from rising up the wall. Point over the holes with lime mortar and leave to dry and cure for between 2-6 weeks.

Replace plaster, skirting boards and decoration. If there has been any evidence of hydroscopic salts penetrating the plaster and brick as a result of dampness, you may wish to use a special type of plaster that resists salts.

DIY Damp Proof Cream

Description

This is a modern rising damp treatment whereby a Damp Proof Cream forms a horizontal barrier against rising damp when injected into the mortar bed joints of a wall. The Damp Proof Cream is most suited for Brick walls, Masonry Walls and Stone walls and can be applied from inside or out.

Drill Install Plug

Directions for Use

Preparation:

1. Repair or install drains to carry away surface water.

2. If internal floors are below external ground level form trenches along the external face of the walls at least 150mm below the proposed Damp Proof Course level (where foundation depth allows). If approach is not feasible the Damp Proof Course must be placed 150mm above external ground level and the internal walls tanked below the Damp Proof Course to prevent lateral migration of moisture/salts.

3. Remove skirtings, fixings and render/plaster to expose the line of the proposed Damp Proof Course (mortar bed).

4. Internal plaster which may be contaminated with hygroscopic salts should be ‘cut back’ a minimum of 1m above the Damp Proof Course line or 300mm above the highest signs of dampness/salts.

5. Check flooring timbers for signs of fungal decay and repair/replace as appropriate.

6. Ensure wall cavities are cleared of debris.

   Application of the DIY Damp Proof Cream:
   

   Placement and Depth of Drilled Holes
   

7. Walls vary in thickness and type of construction so it is essential these factors are taken into account before deciding on an appropriate drilling pattern.

8. Older properties may consist of several different styles of construction and the specification of drilling and injection should be carried out accordingly.

9. Damp Proof Course height should always be at least 150mm above the external ground level.

10. Vertical Damp Proof Courses should be provided to connect horizontal Damp Proof Courses where ground levels change and to isolate untreated wall areas (adjoining properties, garden walls etc.)

11. In most cases solid brick walls may be drilled/injected from one side only.

12. For cavity walls each leaf may be dealt with as separate 155mm thick wall. Alternatively, if preferred, drill through the selected mortar course, across the cavity, then drill the other leaf of brickwork to a depth of 90-100mm and inject in one continuous process (the physical properties of Damp Proof Course ensure the Damp Proof Cream remains in contact with the surrounding mortar bed).

13. Always ensure the cavity is clear before treatment.

14. In random stone and rubble infill walls, as far as practically possible, follow the mortar course at the appropriate level. However, if the stone is of a porous type, it may be possible to vary the drilling location (mortar/stone) as long as the mortar bed perpends are treated.

15. In the walls of greater than 350mm thickness it is recommended that drilling is undertaken from both sides at corresponding height.

16. In the case of drill holes becoming blocked these should be re-drilled just prior to injection or a new hole drilled nearby to ensure than an adequate volume of Damp Proof Cream is introduced

17. Drill 12mm diameter holes horizontally in the mortar bed at centres no greater than 120mm. The depth of hole required for various sizes of wall is shown in the table. For walls of intermediate thickness the depth of holes should be pro rata. Where the masonry is irregular, ensure the horizontal drilling pattern targets the base of all perpends of the course selected.

    Hole depth required for walls of various thickness:

    Wall Thickness	115mm 4.5'	230mm 9'	345mm 13.5'	460mm 18'
    Depth of hole	100mm	210mm	320mm	430mm

    
    

    Injecting the Damp Proof Cream:
    

18. If wall is dry you MUST pre-treat the wall with water. A couple of hours before application fill the holes with water.

19. To inject the Damp Proof Cream use either a caulking gun or hand pump.

20. Use the gun/pump to establish a positive pressure. Insert the lance of the Damp Proof Cream application gun into the full depth of the pre-drilled hole. Squeeze the gun trigger and back fill each hole fully with DPC to within one centimetre of the surface. When treating cavity walls from one side make certain that the holes in each leaf are filled.

    Wall Thickness	115mm 4.5'	230mm 9'	345mm 13.5'	460mm 18'
    DPC per 10m	1 Litre	2 Litre	3 Litre	4 Litre

    Finishing the Job:

21. On external faces of walls drill holes can be re-pointed using a matched mortar or plugged with plastic caps of a suitable size and colour.

22. On internal faces holes can be left open and plaster stopped short of the Damp Proof Course or covered with skirting boards.

    Replastering
    

23. The removal and replacement of internal salt contaminated plaster is an important part of effective damp proofing work (salts left by rising damp are hygroscopic and cause future staining independent of structural dampness). It is essential, therefore, to follow specific guidelines drawn up for dealing with the particular challenges posed by damp/salt affected surfaces. It is advisable to leave walls injected with Damp Proof Cream to dry for as long as possible, and for at least 14 days, before removing excess salts and commencing re-plastering.

24. An integral waterproofing additive should form part of the re-plastering specification.