mass concrete house,chemical dpc's? drylining? and new floors!

byrneos

hello people.
about a year ago we bought a house .
it has 8"solid concrete walls.recently realised there is some damp in the walls/floors .it has concrete floors.its about 80years old so slim if any chance of a damp proof course under floor.

so for the walls im thinking
chemical dpc injected into wall.been reading a bit many say they don't work because wall needs to be fully dry first and if you can do this you don't have a damp problem.
any thoughts on that one.

also
drylining with ventilation gap behind on inside of exterior walls and add some vents.
(exterior insulation out of our price range at moment.)
sound good/bad?

ok the floors either take them up replace with dpc,insulation and concrete again.followed by hardwood flooring.

or use this product http://www.deltamembranes.com/waterproofing_membranes/delta_fm/delta_fm_1.htm
laid directly on to existing concrete floor followed by insulation and hardwood floor.

thing is if i introduce either the dpc under or on top.am i right in thinking the moisture that would have come through the floor before will be redirected out towards the wall.making them more damp and if chemical dpc doesn't work will only be hiding and adding to the build up of damp behind the drylining.

also if i go with the concrete floor should i wait for the drying out period and use dehumidifier to get walls as dry as possible before the drylining goes on?

should i just put drains around out side of house first a see if that helps?

ok i know there is many questions here but any advice would be great or if anyone has dealt with a similar building before and has different solutions...

RKQ

Wouldn't recommend a chemical dpc in concrete. IMO A chemical dpc works best in traditional lime mortar, as the lime soaks up the chemical, to form a solid layer.

Concrete and cement won't soak as effectively.

You might consider some form of tanking, but this would ideally involve replacing the floors, skirting and part of the internal plaster.

The membrane may work.
A perimeter french drain will help.

Exterior insulation might be an answer, as it would keep the conc. walls dry.
Look at options used to convert old basements.
Have moisture readings taken to ensure the problem is rising damp. Seek Professional advice.

byrneos

RKQ wrote: »

Wouldn't recommend a chemical dpc in concrete. IMO A chemical dpc works best in traditional lime mortar, as the lime soaks up the chemical, to form a solid layer.

Concrete and cement won't soak as effectively.

You might consider some form of tanking, but this would ideally involve replacing the floors, skirting and part of the internal plaster.

The membrane may work.
A perimeter french drain will help.

Exterior insulation might be an answer, as it would keep the conc. walls dry.
Look at options used to convert old basements.
Have moisture readings taken to ensure the problem is rising damp. Seek Professional advice.

thanks for the reply!

yeah i thought that the chemical dpc wouldn't suit concrete and a builder told me he thought the same as you.
but any damp proof people all say its ok(it is the product they use/are selling after all)

i was thinking about a tanking system the likes of heydi'k11 or one of the vandex range bb75 or bb55. i was told by someone who wanted to use a chemical dpc. that if i tank the damp would eventually climb the walls until it was over where i tanked up to.

who would you get advice from .anyone ive talked to has given me different solutions funnily enough the one they can do for me.

would a surveyor be able to tell if its rising damp or condensation etc? the one that looked at the house for us before we bought it didn't foresee any of this he even said it was block walls. just a bit wary now.

RKQ

You are very welcome.
A surveyor should easily distinguish between rising damp and condensation.

Lots of old houses suffer from condensation because no one has lived in them for a while.

Traditionally T&g boarding was installed, to dado level purely because rising damp rarely rose higher than 900mm or circa 3ft. So if you can tank to this height you should have a problem.

Underfloor heating and a heat exchanger may also help.

Maintain a 25mm air gap between the wall and the dry lining to prevent mould growth.

I'm sure there are lots of solutions, but I can't really say as I haven't seem the interior.

Maybe if all the sales reps are so confident about their system, they'll be happy to give you the names of satified customers. You could then enquire with them.

Good luck.

byrneos

RKQ wrote: »

You are very welcome.
A surveyor should easily distinguish between rising damp and condensation.

Lots of old houses suffer from condensation because no one has lived in them for a while.

Traditionally T&g boarding was installed, to dado level purely because rising damp rarely rose higher than 900mm or circa 3ft. So if you can tank to this height you should have a problem.

Underfloor heating and a heat exchanger may also help.

Maintain a 25mm air gap between the wall and the dry lining to prevent mould growth.

I'm sure there are lots of solutions, but I can't really say as I haven't seem the interior.

Maybe if all the sales reps are so confident about their system, they'll be happy to give you the names of satified customers. You could then enquire with them.

Good luck.

thanks again!

No6

If its rising damp consider an electro osmotic system, best also to provide a dpm on the floor too, either by digging the lot out or laying one over the existing floor and laying a new screed with insulation over.

Schooby

There is no evidence of electo osmotic DPC's working ever, if you push someone selling one they will tell you that they have never been proven not to work!!!!!!!!

with the concrete construction you really have to take your time in ruling out the potential of condensation.

to make a definitive call in this regard you need to be able to calcultate the dew point in the various locations affected:
Air temperature
relative humidity
surface temperature

there is equipment available to do all this for you but you will be looking at a big outlay
http://www.gesensing.com/products/proti_hymaster.htm?bc=bc_ge_protimeter

If you are willing to go to the lenghts of breaking out solid floors you should consider replacing them with properly detailed very well ventilated timber suspended floors, this will facilitate evaporation from the ground and the base of the walls reducing the moisture content and preventing it getting up into the decorated surfaces in the house.

If it is a condensation problem your heat loss from the house may well be a bigger issue and bigger financial impact over time on heating bills than the damp patches.

SparkeyByrne

Hi There,

Just a quick note on your question on how to determine whether the damp on the walls is caused by condensation or rising damp. I'm no expert but have been trawling the various websites for some time on this issue as am in similar situation (see my post on Cottage Renovation). One of the tests I came across is called the Foil Test. Basically what you do is dry out a small patch of wall with a heater. Stick a small square of tin-foil over the dried patch, sealing the edges with tape. Leave the patch for 24 hrs and remove the foil. If rising damp then back of foil will be wet, if condensation then front of foil will be wet. I haven't tried this myself yet but the logic seems sound enough. The only provision I'd make though is to make sure it's not lashing down outside as this might cloud the results.

No6

Schooby wrote: »

There is no evidence of electo osmotic DPC's working ever, if you push someone selling one they will tell you that they have never been proven not to work!!!!!!!!

with the concrete construction you really have to take your time in ruling out the potential of condensation.

to make a definitive call in this regard you need to be able to calcultate the dew point in the various locations affected:
Air temperature
relative humidity
surface temperature

there is equipment available to do all this for you but you will be looking at a big outlay
http://www.gesensing.com/products/proti_hymaster.htm?bc=bc_ge_protimeter

If you are willing to go to the lenghts of breaking out solid floors you should consider replacing them with properly detailed very well ventilated timber suspended floors, this will facilitate evaporation from the ground and the base of the walls reducing the moisture content and preventing it getting up into the decorated surfaces in the house.

If it is a condensation problem your heat loss from the house may well be a bigger issue and bigger financial impact over time on heating bills than the damp patches.

Schooby while you are quite possibly right I think silicone injection is also hit and miss. I think any one form of chemical or electro osmotic system on its own may fail or suceed depending on the individual case involved. If either system is the only measure utilised the the chances of failure are quite high but as a number of posters have pointed out other measures including reducing the ground level externally and installing french drains or laying footpaths, removing the floors internally and laying new floors with a dpm all contribute.

I do have to say I have used the electro osmotic dpc in a number of projects including my own house and I've had no problems but then again there wasn't major damp problems, its not the only measure used so its more like an insurance and as its not that expensive why not give people a bit of peace of mind.