Fix Damp walls in terrace kitchen extension

[Ferdinand]

A bit of a spinoff from my other thread.

 

I am replacing a back galley kitchen in a 1900 terrace house due to damp over a decade having stained the back of 2 base units. Date is approx 1960-1970 (based on different bricks from house and knowing when my local council did grants), so probably a mix of solid wall and cavity.

 

The plan is to strip out the kitchen, and do some protection against what I expect to be rising damp ni the walls. I can see 2 options:

 

1 - Strip plaster at bottom and Inject DPC.

2 - Do not strip plaster, and attempt to seal with eg "Damp Seal".

 

My inclination is to do both 1 and 2, but I will not have the option of leaving the walls exposed inside for more than 24 hours to dry out as it has tenants in situ. I get a clear week to work but more will be awkward.

 

Potential problems:

 

1 - One wall is external, one is party. Are there difficulties injectnig a DPC into a party wall? Do I need to do a PWA notice etc?

2 - I would like to insulate the external wall as much as is practical, but what is the method? I reckon I can lose only perhaps 25-30mm off the kitchen width, and I really don't want to take it all back to brick even on one side. Can I bond PIR or PUR backed plasterboard directly to the existing plaster?

 

Any comments are welcome.

 

Ferdinand

 

(Aside: may be off line for a bit due to antipodean holiday, or may check in if the marsupials are boring).

Edited September 2, 2016 by Ferdinand

[Onoff]

I had similar in an 1863 terrace kitchen. Injected DPC then. No complaint from the neighbour but then I didn't consult them! Did take back to brick though then painted on liquid DPM - the sort you blind with sharp sand in the second coat and can then render to which I  did. Would EPS not be better if there's any chance of future damp? 

[ProDave]

My only experience with "rising damp" was in a previous 1930's semi. The root problem was a fault with the rendering, the base portion bridged the dpc, it had cracked, some away from the wall, and soil had got into the gap so wet soil was bridging the dpc. the problem was compounded by the previous owner sticking polystyrene tiles to the wall to "hide" the damp and wallpapering over that.

 

Stripped off the wallpaper and tiles, fixed the rendering and dpc bridging and it dried out fine.

 

Check outside first that the ground level is not above the dpc and there are no leaking downpipes.

 

If it's behind kitchen units, I would strip off the old damp plaster up to worktop level and leave it as bare brick behind the units. Try to install some vents somewhere to allow some air movement behind the kitchen units perhaps.
 

[Nickfromwales]

Plus one on liquid DPM and then dot and dab EPS backed plasterboards onto the 'cold' / external or non-cavity walls. The issue is probably warm humid air hitting the bitterly cold and unventilated areas, such as the backs of the units and plinth level etc. 

 

[tonyshouse]

For me no dpc injection or dpm etc, yes to thermal lining though min 50mm insulation, prefer more 

[Nickfromwales]

3 hours ago, tonyshouse said:

For me no dpc injection or dpm etc, yes to thermal lining though min 50mm insulation, prefer more 

From a practical point of view, even as little as a 40mm board ( 9.5mm plasterboard and 30mm EPS ) will make a huge difference. 

Big consideration is making sure to foam the bottom and top thoroughly to stop convection air flow behind the dabbed boards. 

 

[tonyshouse]

From a regulatory view point it does not pass.

[Ferdinand]

4 hours ago, tonyshouse said:

From a regulatory view point it does not pass.

 

Given that the galley kitchen is 1.72m wide with 2 runs of base units and a .5m 'corridor', I think I can qualify for exemption under the "required for functional room" exemption - should I have to have the argument.

 

Or I could just leave it uninsulated and take off less than 25% of the plaster to avoid the rules :-) (which would not be ethical imo).

 

In practice I will probably use something like Celotex PL4025 or PL4015 (25 and 15mm of PIR plus 12.5mm plasterboard resp.) dot and dabbed on the external wall only.

 

My only other alternatives would be EWI (difficult) or to replace one side of base units with wall units, which would cripple the kitchen.

 

Ferdinand

 

Edited September 2, 2016 by Ferdinand

[Nickfromwales]

13 hours ago, tonyshouse said:

From a regulatory view point it does not pass.

Agreed.

This doesn't sound like it needs BR involved though, and an annoyance that someone would make you do things a particular way IF you chose to make an improvement when they haven't recommended or enforced that improvement in the first place.