rising damp problem

[JohnD]

it is very likely that your solid floor is carrying damp.

tape a piece of clear plastic tightly to it and see if moisture forms on the underside

although an 1880s house might not have had a dpc in the walls, moisture usually evaporates off the bricks provided they are uncovered. In your case there can be no evaporation from the inside surface, and the floor is probably adding more damp.

 

[Joe Malone]

Given the age of the property I've got to assume it's a retrofit concrete floor but correct me if i'm wrong?

Retrofit concrete slabs cause huge problems with damp in old buildings because it's virtually impossible to properly connect the dpm to the dpc, I've not seen one retrofit slab yet where the dpm has been properly detailed into the dpc.... of course i'm assuming it has a DPM fitted, if it hasn't then this is even worse. The problem with concrete slabs is that they displace all the moisture underneath and force it up the walls under hydrostatic pressure. The gap left between the dpm and dpc forms the moisture pathway. On top of this it sounds like you have black ash mortar which is extremely porous. Bear in mind that black ash mortar will always give high damp readings with a moisture meter due to the fact that it has a high carbon content. These meters work on electrical conductivity not damp.

I really need to know if the building originally had a timber floor and if the walls were originally finished using lime plaster? What plaster finish is currently on the walls and does the building have a physical dpc fitted. Are there any redundant airbricks at low level?
If you can provide me with this information then I can give you detailed advice about what you should do.

 

[Joe Malone]

Incidently JohnD is on the right track with the test he's suggesting but his test is very arbitrary and won't actually tell you a great deal, there will be damp in all floor slabs to some degree but you need to know if it's damp enough to cause a problem. I use a piece of kit called a humidity box for testing moisture contents on floor slabs. It's sealed onto the floor for at least an hour then I plug a Hygromaster into the box which gives me a relative humidity reading inside the box. Anything above 75%RH and the floor is considered to be damp.

 

[Joe Malone]

Natasha has recommended electro osmosis so lets look at this as a course of action...

Electrical charges in rising damp vary widely depending on the types of salt present. To be effective therefore, an electric osmotic current will have to be varied as appropriate along the wall, and this would appear to be impracticable. Another problem with this method is that the potential is sometimes reversed relative to the direction of the water flow (Richardson, 1991)
In addition it has proved difficult to demonstrate convincingly the effectiveness of passive systems in the laboratory. Moreover, there is still a lack of evidence that any electric osmotic system has been significantly successful. For these reasons, electric osmotic systems have not been given official approval by the Building Research Establishment or the British Board of Agrement.

 

[^woody^]

Prosystem device emits weak low frequency electro-magnetic waves into the walls

Have any tests been done to determine the effect on whales - ie will this affect their navigation if used in coastal areas? What about moles and dogs - is this system humane?

I think there are two reasons to avoid these systems (Woody, 2006)

1. Unproven effect on animals
2. They are a waste of money and don't work

 

[Joe Malone]

I don't know, I've never considered damp proofing the dog!

 

[JohnD]

I think he was worried about the effect on Wales.

 

[^woody^]

I think he was worried about the effect on Wales.

Intresting.

A low frequency wall from Chester down to Chepstow, I think this needs investigating

 

[noseall]

so, is Offas Dyke high frequency then?

 

[JerryM]

you've both got me really confused with your arguments

MK85,

this isn't really a job to do diy. i suggest you get 2 or 3 quotes for damp proofing the house. make sure they are national companies or tied to a national company if local. also make sure that the guarantee is insurance company backed.

my gut feeling is that your floors and walls will need treating. there are various methods of sorting (as you've seen Joe has his and i have mine). what i've found key is not the chemicals used but who does the work.

get the quotes and repost to get clarification on them to enable you to clarify the detailed specification for the work. by doing this you will be able to avoid clear pitfalls through selecting the most competent installer.

for example some installers take the plaster down to the floor level - this is a disaster as it leads to bridging

my gut feeling would be to tank both the floor and walls but as I’ve said other methods will be equally as good and potentially more cost effective. Until you get quotes you can’t be sure what's the best way forward. you may also need to start thinking about potentially putting in new concrete floors and this would be a relatively big job

 

[Shytalkz]

so, is Offas **** high frequency then?

Isn't the anti-naughty words thing great

 

[noseall]

so, is Offas **** high frequency then?

Isn't the anti-naughty words thing great

how can a historic landmark be considered offensive

mind you......

 

[Shytalkz]

Ah, but if you spell it Dyké, it beats it. Bit overzealous, wonder if it accepts Scunthorpe...