How treatable are the typical types of damp and are there any that can never be completely prevented or eradicated, e.g. in basements of old period properties?
Rochester Building and Damp: All damp can be eradicated; never believe anyone who tells you otherwise. Damp encompasses a myriad of perceived issues within a property. It is not a singular entity that can be treated with a miracle product installed by an unscrupulous company. Damp requires rectification through identification of the source and a specific course of action that ensures it will not return.
The ideal solution for a damp basement would be to expose the retaining perimeter walls below ground-level externally and treat accordingly. This course of action would be prohibitive for many reasons; but that’s not to say works completed internally within the basement which suppress and conceal are not a cure. If works inside the basement are completed effectively and the ingress is indefinitely suppressed, then you don’t have damp in your basement.
In regard to typical occurrences of damp; it’s all reasonably straightforward to fix. Although be aware, invasive works will be accompanied by dust, noise and building materials being brought into your property.
It should be noted that in many instances, rectifying the cause of damp can be quick and easy; a missing roof-tile for instance. However, invasive works may still be required if rainwater from that missing tile has caused major damage to the ceiling and plaster in the bedroom below.
Are damp prevention measures ever worth investing in before I have a problem or is it more economical to wait until treatment is needed?
Rochester Building and Damp: This is entirely dependent on personal circumstances and I don’t just mean finances. If the lead flashing has come away from the parapet wall, with potential to cause a direct ingress into the small rear bedroom, then jump to it and have it fixed. However, If intending to purchase a property free of damp; then deciding to have a chemical injection DPC (damp proof course) installed “just in case would be unwise. Perhaps you intend to purchase a property with an external ground level which quite obviously bridges damp proof course, but nothing has been picked up during the survey and on close inspection there is indeed no ingress within the property. Under these circumstances, it would be prudent to refrain from pursuing remedial works. There is no ingress present, it’s spending money on a problem that doesn’t exist.