Finding the source of damp

[Aaron]

Hi all, the damp is on an exterior wall garage / extension. There was previous water damage from a leaking roof. The roof has been replaced, drainage sorted but 2 months after the plaster has been put on we are getting signs of water through again. The moisture meter says 75 but we are using a de-humidifer and that has reduced it to 62 within 4 hours. We had a damp report done back in March and that did not identify any signs of rising damp on the property but now are unsure about what to do next. 

[JohnMo]

Have you reviewed the level of the DPC compared to the outside ground level. You really need the DPC 150mm above the outside ground level. The second to last photo looks to have gravel way above the floor level.

 

Do you have any insulation in the building?

[Aaron]

It is the neighbours property, when we did the floor of our property we did not find DPC. Do you know how we would go about installing it? 

We have put insulation in now, cavity wall and in the ceiling, and loft. It may be worth noting that the property has not been heated in quite some months.

[Dave Jones]

solid wall with paint on it. No cavity, no insulation. Does the wall even have DPC ? garages dont need one for regs.

 

any temperature difference between inside/outside will immediately get that wall damp with condensation, a lot of which will be inside the wall.

 

Strip of the plaster, stud and insulate then board and plaster again.

 

 

[markc]

I would say the water is coming in under the wall due to the outside ground level. If it’s on the neighbours side and you can’t dig and install a drain then you are looking at tanking or drainage membrane on your walls and floor to take the water away.

[Aaron]

As it is not rising damp, damp course injections would not help correct?

[markc]

5 hours ago, Aaron said:

As it is not rising damp, damp course injections would not help correct?

Correct

[JohnMo]

Not seeing a damp proof membrane either, is that going on the concrete floor before the insulation? Or is that the finished floor height?

[Aaron]

After having 7 different professionals come out, we have about 5 different opinions on how to tackle the problem. 

 

- Hack off the plaster to 1.2M above the internal ground level

- Tanking membrane or tanking slurry (apparently better than DPC or DPM) along the length of the wall 

- Put damp course injections in at the height of the first block above ground level

- Use Anti-condesnation paint by Permaguard

- Put DPM down on the floor after concrete and self-levelling, before underlay and flooring

 

I really hope this covers all avenues? We may have to render the outside wall or re-point and re-paint the neighbours side. 

[ProDave]

So you have "converted" a garage just by plastering the inside of a single skin brick wall that may not even have a DPC, kept the original concrete floor without building up the level and adding insulation? and the outside ground level appears to be too high.

 

Who has done this work, and more importantly who "designed" this conversion.

 

Just about everything done is wrong.  Strip off the plaster, then start again properly designing the conversion and getting it right this time.  This forum will give much better advice how to do it properly than anyone that has been near it so far.

[Aaron]

@ProDave this is an interesting assumption, and an incredible amount of judgement for an open forum for people who are learning on this journey. The industry being filled full of people who do things differently, shoddily, and with poor advice based purely on their experience is the reason we, as homeowners, cannot trust the advice presented. 

 

The conversion was already in place, there was an existing kitchen where we intend to replace this. The builder who was used has already been removed from the project and the plaster has been removed. We have sought the guidance of multiple damp specialists. My intention here was get some perspective around the different recommendations provided from all of these people. 

[ProDave]

I think generally most of us shudder when you say "Damp Specialist"  They want to sell you their solution to solve the problem.  How many will be blunt like I was (sorry if I offended you) and tell you that what you have is a total bodge, has been done completely wrong, and needs ripping out and starting again with a proper conversion of the building.  That is not something some magic damp solving product will fix. It wants a fundamental re design and rebuild.

 

If you did just adopt some damp specialists solution and continue as it was, you would still have a very substandard very poorly insulated, cold and expensive to heat room.  Is that what you really want?  Or would you like to do it properly and have a nice warm dry kitchen?

[saveasteading]

7 minutes ago, Aaron said:

 this is an interesting assumption, and an incredible amount of judgement

Hi Aaron. No need to take offence, as you know it wasn't you. Even if it was, we are all learning

 

All on here are reading and commenting in their own time, perhaps limited time. I've made many wrong assumptions, through not reading and rereading forensically like I would if doing it professionally. Also, I'd insist on a site visit if I was.

 

I've no more to say though as the advice seems to be good. 7 different opinions is no surprise as there may be a number of solutions, or none at all.

[jayc89]

No amount of damp products will fix that, sorry. Please don't add insult to injury and get drawn in by their sales pitches, those products just don't work (not for long anyway). The source of the damp needs fixing, not the symptoms.  

[Mr Punter]

If you have a properly designed and installed type c drained cavity waterproofing system the room would be dry.  It requires the membrane on walls and floor, a perimeter chanel plus a sump / pumps if you cannot drain via gravity.