Bright Walton posted an update 1 month ago
Have you noticed that paint is blistering off the walls? A damp patch has appeared under the window sill? You have tried to paint it over and over again but it just keeps flaking off the walls? Maybe you have decided to bite the bullet and call in a damp proof expert to give you advice? That’s a great idea but best to know if the damp proof expert is giving you the right advice. It could be a time consuming and expensive mistake if you do not know how to damp proof in theory.
We are now going to have a quick look at how to damp proof, what to look for, the damp proof products available and how these damp proof products and systems can solve your damp problems.
So we first need to identify the damp areas of your job and what is causing them. Now this can be tricky but we can eliminate some obvious damp proofing elements before we pay for someone to come and and consult us.
Damp walls at high level or in an isolated area? Is the damp area manifesting internally at a high level? Check outside for condensation overflow or toilet overflow pipes dripping down the brickwork. The constant source of water against your brick work can be drawn into your internal finishes and manifest like a damp patch or salts coming through. This should be obvious so stop it immediately and then once this has been achieved then it will just be a matter of re-decorating your damp wall. Another culprit here is the leaking gutter or down pipe, same again stop the external source of damp and your problem will be rectified. Damp walls can also be a problem and water ingress into your property can also be through structural defects. This is more difficult to ascertain so here is are a few things to look at: Chimney flashing or other lead flashings under windows, cracks in the walls – may need structural repair – consult engineer, defective pointing- could be a major problem – need professional advice, loose tiles – obviously a instant source of dampness in structure needs, bridging of a cavity wall with rubble
All the above except the cavity wall bridging may be able to be visually checked as a source of damp problems. However it may be worth to make sure getting a chartered surveyor to provide you with a full report.
pdc damp proofing which you may encounter is condensation mould cause by lack of ventilation in the property. Usually found behind cupboards or in the corners, condensation problems look like black spots and can easily be confused with rising damp. Once again ventilation is a job for an expert and modern properties which are governed to be more air tight do suffer as a result. A qualified surveyor should be able to point you in the right direct here as with the structural defects.
The biggest problem in the damp proof diagnosis is high ground levels over the top of your existing damp proof course or lack of a damp proof course in the first instance. If you do have high external ground levels then you must lower them otherwise you could be dealing with more than damp walls, you could in a worst case scenario have water entering your property. If you cannot remove the ground then you will need to use a waterproofing technique like you would in a basement.
Now we are getting an idea of where the damp may be coming from lets look at "how to damp proof" with the knowledge we have just attained.
What is the damp proof course? How do I deal with my property if it isn’t working or doesn’t have one?
In the "how to damp proof" guide this is the first point which should be established. Do you have a damp proof course and what to do if you don’t. The damp proof course or dpc is a physical barrier either slate in old properties or in newer properties it is a hdpp or hdpe membrane about 150mm thick and situated above internal floor levels inserted into the mortar course 150mm above external ground level. This dpc is essential part of construction and stops rising damp (dampness tracking up from the ground) and manifesting itself as dampness internally in your structure.
If your dpc isn’t working or is not existent you will need to re-instate it or install a cavity drain membrane to deal with the dampness internally. To reinstate the dpc you can either physically cut it into the mortar course and replace with slate packing (an experts job their a few with the skills to perform this task) or most commonly insert a chemical dpc. The insertion of a dpc is the job of a damp proof specialist. The insertion is achieved by drilling holes externally usually about 20cm apart to the depth adequate for your wall and inject either a damp proof liquid or cream to form a barrier preventing the movement of dampness. Technology has moved forward with the advent of dpc creams which tend to be a better bet than other liquids but beware they are not fool proof and still should be installed by someone with the adequate training. The insertion of creams or liquids can be messy and time consuming as it involves "hacking off" damp plaster to a height usually 1.2 m prior to injection then re-plastering with a salt retardant additive in the mix to prevent the salts coming through afterwards. The real problem is here the wet trades and drying out times involved before you can go and redecorate. Ask the contractor doing the damp proof work what form of guarantee they are going to give you as well as different schemes do vary.
Next option on how to damp proof is to use a cavity drain membrane. These membranes are dimpled sheets which can receive a direct plaster finish or plasterboard finish. This type of damp proofing is a physical barrier mechanically fixed internally and the air gap allows the wall to "breathe" thus all the dampness can come out without staining or guess work that the cream alternative offers. So it acts as a barrier for the surface area covered not just a line across the mortar joints. This damp proofing material can also be used externally to prevent driving or penetrating rain/moisture coming through porous brickwork, defective mortar courses. The cavity drain membranes on the market vary in thickness of dimples from 3mm to 8mm. These products will cover all bases in terms of not allowing the dampness to effect internal finishes and can be applied with minimal surface prep and little to none drying out times. You will however need to identify the source of damp walls (like defective gutters) for the sake of the property in general.