Moisture in walls

[Jay Barrow]

Hi,

I’ve been re-doing our lounge. Building is old stone (1ft thick) walls that have been lined with stud wall and plasterboarded. I ripped down the plasterboard to insulate and discovered rotted stud work at the bottom so I’ve cut it out and replaced. Pretty sure this was due to leak around windows which I’ve sorted and drainage outside which I will sort. I’ve also put a couple of air bricks in to increase ventilation. However, I decided to line between the stone wall and stud wall with a damp proof membrane prior to insulating - see photo (intention is to then put a vapour barrier up before plasterboarding). The problem is I have moisture forming on the inside surface of the damp proof membrane. I’m not sure if this is condensation due to the temperature difference of the room compared to the outside wall? If so, once a vapour barrier is up and plasterboarded, will this stop the problem from happening? Or am I better off ripping down the damp proof membrane and leaving the stud wall more exposed to airflow?

Thanks

 

[bobasd]

i dont like double walls similar to what you have done - once you build an extra wall to "cure a problem" you can then introduce more variables to affect the problem. eg. you knock more holes in the wall when the idea is a warmer room.
lots of times what you are doing will work fine but fwiw, my firm wont do it in case of expensive call backs a year later.


1. how was the wall stone surface finished before this recent work?
2. is the floor solid?
3. is your FFL higher than the ground outside?
4. can you show a pic of the whole wall - any door or window openings included?
5. perhaps you would post a pic of the exterior of the wall?

 

[martin hill]

If you put a vapour barrier between the outer wall and stud work you are locking in the moisture which will rot the wood. Rip out the damp proof membrane and see if outer wall wet/damp. leave it to dry out and if it stays dry you maybe better getting it dot and dabbed with insulated plasterboard straight onto the stone.

 

[Jay Barrow]

Thanks Martin I did wonder that. I’ve put a vapour barrier on the warm side of the insulation as well. I figured that the moisture build up on the damp proof membrane was just condensation as it can’t be anything else. In theory, once the vapour barrier is on the warm side will this prevent condensation if I left the damp proof membrane between the cold side and stone wall? Or am I still better taking the damp proof membrane out?

Bobasd- walls were finished in this way before I did the work. I have not put the stud wall up, just replaced rotten bits. The existing wall behind the stud is in no way suitable for dot and dabbing due to the state of them, and significant work would need to be done to do anything other than have a stud wall. Floor is a floating floor and ground height outside is similar, if not slightly higher than FFL, but I intend on sorting that out. I hear what you’re saying about not liking this double wall method, but given the building it’s the only practical and economical way to do it.

 

[Guitarguy]

The thing is due to the age an construction of the house, you’ll never win against damp you can only really take steps to manage it. There is probably not a damp proof course in the wall so any moisture getting in needs to be able to get out otherwise you’ll get issues like you’ve found.
Might be an idea to get the wall stripped and lime rendered to allow breathability

 

[martin hill]

Jay i would take it all out and start a fresh. First job would be to have the outside ground level lower than the floor inside. You could dig down about a foot and 6 inch wide if possible. My garden at the back is level with the kitchen floor but with it being thick hard clay i did that and it's been dry for 15 years. If you do the stud wall again use tanalised timber and on the floor plate put a dpc down first and then timber over it. The upright timbers will need to be braced to the wall but dont have the timber touching leave an air gap
Use these https://www.screwfix.com/p/sabrefix-safe-end-frame-tie-10-pack/91531. for the timber to wall. May be a good idea to put some air bricks in if you can.

 

[Jay Barrow]

Cheers Martin,

Ive already fixed DPC to the floor plate and put in three air bricks. Outside ground level is next on the list. I’ll rip out the membrane between the stud wall and outside wall thereby preventing the condensation problem.

 

[martin hill]

Are yoo taking out the timber and starting a fresh ?

 

[Jay Barrow]

I’ve already replaced the rotten timber, so just planning on ripping out the damp proof membrane.

 

[martin hill]

A coat of timber treatment maybe a good idea.