Victorian Damp Mystery

[KevinG]

Hi there, I am buying a red-brick mid-terrace house in Dublin built c1886. The house has been unoccupied for five years+ and is in need of full refurbishment.

 

I am trying to figure out the root cause of some damp issues. It appears in two areas: towards the front of the house (hard to explain) and at the back (due to a dodgy extension).

 

Layout

 

The house is high off the street (3/4 steps) but the houses on the row behind are at a higher level.

 

The house is a two-up two-down. The front reception room has suspended wooden floors. There is a brick air vent under the floor out to the front of the house.

 

The back reception room has a hard/concrete floor.

 

Q1 - does anyone know if that hard/concrete floor could have been original? There is no indication of other work on the original piece of the house, but the house is so old I don't know if it may have been filled in at some stage.

 

There is a hall, kitchen, and bathroom at the back of the ground floor. The kitchen was definitely added (maybe 40 years ago). I'm not sure how much of the hall/bathroom was in the original layout).

 

Damp

 

The damp at the front is on the interior wall of the Entrance Hall. It looks like 'rising damp'. See photo.

 

Q2 - if I intend removing this wall (as not load bearing), do I need to take any further action? What is the possible root cause of this in an internal wall? As it connects to the front of the house, can I connect it to something in the brickwork of the front wall?

 

There is damp along the original exterior wall between the Living Room and Kitchen. The assumption is that the concrete floor of the Kitchen is bridging the damp. There is damp on other walls of the extension too.

 

Q3 - for damp on the wall between the extension and the original back wall, I'm assuming I can dig out the floor on the extension and add in a DPM?

 

Q4 - for damp on the outer extension walls, do this condemn the whole extension and require a rebuild or is it fixable.

 

Thanks!

[TonyT]

I personally don’t believe in rising damp, I’ve done a few training courses with Mike Parrett Associates, and generally lack of maintenance, improper use, lack of heating and ventilation can lead to ‘damp’

 

get some windows cracked open, get some heating on and check rainwater goods to start with, ground levels are correct etc.

 

do you only have 1 air brick? Good cross flow is needed under suspended timber floor.

 

 

[KevinG]

Thanks TonyT - yep it looks like one airbrick at the front. Which is why this back concrete floor confuses me and if it was always there.

[Mr Punter]

49 minutes ago, TonyT said:

do you only have 1 air brick? Good cross flow is needed under suspended timber floor.

 

It is probably not going to happen as it is a terrace with higher ground and solid floors at the back.  I would guess it is the same all the way along the street.

 

I would like to remove all the floors, dig out at the back and get all floors levels to 130mm below where you want your finish.  At the front you will need to make the level up and you could use hardcore from the back plus some MOT or sand.  Use a wacker to consolidate the floors.  Lay 1200 gauge DPM and lap up the walls a bit.  Lay 100mm Kingspan type insulation.  Lay 22mm chipboard as a floating floor, leaving a 15mm gap at perimeters and your chosen floor finish on top.

 

If you have services running in the floor you can have some areas of, say, 2 x 50mm insulation and cut the runs out.

[KevinG]

Thanks, Mr. Punter. I really appreciate your help. I am an amateur in this game but learning fast. Does that approach basically mean no concrete floor?

[Mr Punter]

Yes @KevinG.  I don't see the need in a concrete floor if the ground underneath is decent and not too wet.  The walls are (I hope) supported on foundations, so the floor just needs to be stable, dry and well insulated.

[TonyT]

Look for the source of the problems before coming up with a solution, as you may end up doing unnecessary work

[George]

Damp at the base of wall is often interstitial condensation due to the wall being a few degrees colder - it is in contact with the ground between 9-11 degrees. A concrete floor will tend to chill it a further. Once condensation arises, this will conduct more heat away creating a feedback loop.

 

Lowering the relative humidity and raising the internal temperature to warm more of the wall is the most straightforward solution. Lime plasters are also needed as they are resistant to water damage and will allow the wall to dry out once it is warm and humidity is lower. 

 

Other solutions such as removing DPMs/concrete and replaced with limecrete or earth floors certainly help, but I personally don't subscribe to the view that water is 'forced up' into the walls because of dpm/concrete floors. I think they help because limecrete/earth floors don't chill of the base of the wall and they also buffer humidity. But this is from my own observations/experience not testing!