Strange musty earthy smell in hallway but can find no signs of damp

You want someone who understands how to deal with older properties and the way that the materials used work, as opposed to today's tradesmen who are mostly used to working with modern materials which do not work so well in older properties. It sounds like the house drying out, but will take a lot longer if parts of the exterior and interior are covered with modern building materials. The walls will be lime mortar but may have been repointed with a cement. This will stop the walls breathing and will hold water in the wall causing dampness. They have probably had the internal walls replastered or drylined, rather than the lime plaster that would have been on them - again, this can trap water behind. Now the weather has been so hot, any trapped water in the walls will be gradually drying out. It may have had an injected damp proof course, this seldom works in this type of property. Most modern materials and methods are designed to cover up and seal the dampness in the walls rather than allow the walls to breathe. Most older materials, although still available, are generally a lot more expensive and harder to use, while finding someone able to use them are harder to find. Lime mortar does not contain cement, although continually come across so-called experts that make up their lime mortar with cement or add water proofers etc. This defeats the purpose of putting in lime mortar as any additives will render the lime mortar, plaster render ineffective and a total waste of money. Most tradesmen today are trained in modern building methods and the public's need for instant solutions. Brickies, stone masons are trained to build with hydrated lime and sand thinking this is lime mortar, rather than hydraulic or non-hydraulic lime which is required in order for the lime mortar to set. Hope this has helped you understand your building. Good luck Alex

Further to ADR comments you can sometimes find moist earth under the subfloor timbers which is nothing to worry about. As you can appreciate though, as this dries out you can occasionally get smells seeping up through boards especially orally if there is not cross flow of air to the subfloor.

Curing damp in buildings is generally simple, but requires the expertise of someone who understands building physics especially moisture in buildings. There are five steps to solving this problem (if it is a damp issue in a building). 1) Find someone who understands moisture in buildings, specifically historic buildings (they have subtle differences to modern buildings). Check out ADR Property maintenance, Durie Heritage and SPAB. 2) Find the source of water causing the damp. 3) Stop the source of water 4) Let the building dry 5) Redecorate affected areas Diagnosis without a detailed survey is difficult. However here is a made up scenario for you. Lets assume the floor structure is suspended timber with the end of the timbers in the masonry wall, supported on sleeper walls to reduce deflection. Now lets assume the absolute humidity under the floor is high. (high outside humidity, high rain fall resulting in a moisture reservoir etc.). Also assume the void under the floor has insufficient ventilation (blocked or partially blocked air bricks) Now you have high humidity under your floor that is not reducing. The moisture in the air under your floor, is condensing on, being adsorbed upon, the timbers that support your floor near the potentially cooler, less ventilated bearing points. When this water vapour changes state to liquid water, you have part of the conditions required for mould growth, the other being a food source for the mould such as the floor timbers. The mould now grows and releases spores which you are smelling. As the mould grows there will be higher adsorption of moisture (the mould will collect water vapour). As the timber gets a higher moisture content it will begin to loose moisture by evaporation. This evaporation causes the timber to become cooler (a bit like a human sweating to cool down) Cooler surface temperatures may get closer to a point where water vapour turns to liquid water (the dew point). Now the floor timbers are becoming a perfect breeding ground for even more mould, resulting in a stronger smell. Please note this is just a fictitious scenario. It was written to express the complexity that may be faced in finding the cause of damp. The complex nature becomes more simple with the knowledge of the companies mentioned above. How do you cure the real problem? Contact someone who understands building physics and the relationship between historic buildings and moisture. They will use the best knowledge, the best moisture meters, absolute and relative humidity meters, their eyes and nose and give you a cause to your problem. You can then choose the right people to fix the problem that has been identified. When you have a great person identify the root cause, would you be kind enough to share the problem and solution. This may help us all learn a little bit. Many thanks Ecohaus