Concrete floor - damp problems. Advice needed.

[Debk 10]

We have damp on the concrete floor around the base of a stone fireplace in a cottage dating back to 1700's. It is causing the stone hearth and back of the fireplace to have damp marks on them. It is a party wall with our neighbours.

 

Can anyone advise how to treat this (we may have to take the fireplace out) I want to lay a wooden floor in this room but am loathe to do this with a damp problem. I have read up on damp proofing concrete floors but there seems to be a lot of conflicting advice about painting on sealants , using membrane systems etc.

 

The builder who installed the fireplace says it is because the water level around the cottage is high and we will never be able to fully eradicate the problem but this doesn't seem right.

 

Or, can you recommend anyone who may be able to help or advise?

[carosio 186]

I had a similar problem in the rear porch of a house. I drilled the floor at 6"-8" intervals and though a funnel poured silicon damp course fluid into it to soak the subsoil beneath, the concrete was about 4" thick, and also drilled the adjoining wall about 6" up. This reduced the problem quite a bit. Assuming that your ground level outside is at or below the inside. I'm sure though you'll get plenty of advice from the builders on here.

[Debk 10]

Well I have looked at the concrete floor and I think it is just about at or maybe even below the outside level, although I think the concrete may only be about an inch thick in places. Maybe someone can advise if we will need a new concrete floor laying or can use a membrane and screed or something?

[carosio 186]

Depends what sort of area it is, but if it's not thick as you suggest I would consider breaking the affected area it up perhaps excavating some subsoil out then laying a membrane then concreting to the original level.

 

Probably best to get someone in to advise as there are so many unknowns here.

[janlizzy 10]

Well I have looked at the concrete floor and I think it is just about at or maybe even below the outside level, although I think the concrete may only be about an inch thick in places. Maybe someone can advise if we will need a new concrete floor laying or can use a membrane and screed or something?

 

Have it tanked and no damp will penetrate it.

[carosio 186]

Have it tanked and no damp will penetrate it.

 

Tanking does work, I used a waterproofing additive in the concrete mix but this was in rooms without plaster and then strapped to take the plasterboard.

[handypandy 14]

Because of the age of the property, I would not rush into anything here. As has been said, there are many factors to take into consideration. For example. Portland cement was not used until the 1800's so it is likely that any 'orignal' products (or remedials done since) here are lime based. I wouldn't go down the tanking route yet. Certain lime products have to 'breathe'. Some damp patches are normal in such cases and will (and should be allowed to) dry out naturally. Sometimes, when being the temporary custodian () of such a property, it is a modern cross you have to bear with a smile.

 

I suggest that you do a bit of homework yourself and visit the English Heritage website, there may be info in the repairs and maintenance sections that will help. Only trades with experience of heritage or listed buildings (even if it isn't), should be relied on for correct information on properties of this age.

 

You could (if feasible) start by trenching around the outside of the property to a depth of about a foot below the inside floor level and fill with gravel/ pebble etc., which would certainly help drainage.

 

 

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[Debk 10]

Because of the age of the property, I would not rush into anything here. As has been said, there are many factors to take into consideration. For example. Portland cement was not used until the 1800's so it is likely that any 'orignal' products (or remedials done since) here are lime based. I wouldn't go down the tanking route yet. Certain lime products have to 'breathe'. Some damp patches are normal in such cases and will (and should be allowed to) dry out naturally. Sometimes, when being the temporary custodian () of such a property, it is a modern cross you have to bear with a smile.

 

I suggest that you do a bit of homework yourself and visit the English Heritage website, there may be info in the repairs and maintenance sections that will help. Only trades with experience of heritage or listed buildings (even if it isn't), should be relied on for correct information on properties of this age.

 

You could (if feasible) start by trenching around the outside of the property to a depth of about a foot below the inside floor level and fill with gravel/ pebble etc., which would certainly help drainage.

 

 

.

 

Yes thanks. We have realised that we have to be careful here. On all the downstairs walls we have used a breathable membrane system with lime plaster. This has taken much longer and cost much more than we initially thought. We have done this to a height of 5 ft but are not sure how to tackle the floors. I will look at the English Heritage site as you suggest. If anyone has experience of damp proofing floors in old properties please get in touch.

[spider1 11]

The ground out side the propety mus be 6inch lower than the inside. Water from the outside is draining in only cure lower outside ground level. Forget anything else until this is done. You want a mini digger and driver forget about tanking etc . Get your first builder back for advice as he seems to under stand the problem end off. Talk about bodgers.

Edited January 27, 2014 by spider1

[Debk 10]

the property is joined to our neighbours on one sire the other is straight onto the pavement so I think a call to the council is needed. It is not damp in the area near the pavement or in other rooms that are "lower" than the pavement at the other side of the property.

 

I need someone who has experience to come out and advise us. (our builder not really sure on this point) Any recommendations?

Edited January 27, 2014 by Debk

[hyper 10]

I'm no expert, so as a layman, it sounds like it's the rising of the water table rather than rising damp throught the walls or Condensation. The fact that there is a party wall means that even if you dig away at the floor and install floorboards with joists, the rising water table in your neigbours is always going to affect the party wall and fireplace. So the builder who said it cannot be cured may have a point.

 

Be careful with English heritage, they may get on a mission to list your home, meaning you are not able to do what you want.

 

 

Like I said, I'm no expert though

[carosio 186]

It is a party wall with our neighbours.

 

A member on another thread warned about "The Party Wall Act" when contemplating doing work in this area.

 

The builder who installed the fireplace says it is because the water level around the cottage is high and we will never be able to fully eradicate the problem but this doesn't seem right.

 

Did he give his opinion before or after installing the fireplace?