UKH

Asking this here because UKC people know about everything!

Last year we bought our rental house and we'd like to renovate the kitchen at some point in the future as it's all a bit cheap and tatty. However, we have a damp/condensation issue in there, which we'd like to get sorted at the same time as I wouldn't want the new kitchen to be damaged by damp/mould (and it would be nice not to have to store all our flour etc in sandwich bags to stop it going mouldy!).

I think the damp issue might be related to the fact that it's very cold and there's a massive temperature gradient, though it might also be coming in through the walls. For info, the house is a c.140 year old stone terrace and the kitchen is a pitched roof single story room sticking out the back, hemmed in on two sides by external stone walls, and getting pretty much zero sun. In the winter it's freezing and in the summer, the cold side of the room (aka the one furthest away from the window) ends up with pools of condensed water on the floor. What I'd like to know is whether having internal wall insulation fitted would be likely to substantially improve the situation? What would we need to consider when having something like this done? 

Thanks in advance!

Short answer is I'd use the property as a launch pad and move on in a reasonably short period of time.

The floor I'm guessing might not have a damp proof membrane or any insulation below the existing concrete slab. Damp will rise and evaporate moisture into the warmer air and it will also add to the damp creeping up through the base of the walls. The fix would be to dig up the floor, insulate with a layer of 100mm Kingspan and add a D(damp) P(proof) C(course) in the form of a heavy visqueen. The new concrete will now be insulated and damp proofed.

The walls will have no cavity. Remove all plaster on the walls back to the brick. A damp proof injection job in both the external stone and internal brick will help, don't use Drizone gel as it doesn't work as well. You can hire the machine and buy the chemical yourselves but stick to the instructions.

Insulated plasterboard with a foil back can be fixed to the walls using 2 methods, I won't go too much into them. Fit an airbrick at low level to allow air to flow behind the kitchen units, 2 airbricks will improve the flow massively.

Feel free to contact me directly for more advice, I have 31 years experience but no longer do these types of jobs.

Hi, funnily enough I'm in the same situation with my renovation and could do with some  advice. I've smashed / dug the floor out and am doing what you suggest there. However with the walls I've heard that injecting damp proof courses doesn't achieve much, I've got the walls back to brick and was planning to apply tanking slurry over the bottom half of the walls over lapped with the dpm on the floor.  Then overboard using sticky foam to stop cold bridging and leaving a ventilation gap behind the skirting boards. After talking to my building inspector he told me not to use insulation as the idea is to allow the walls to breathe. 

Hi, if you do rip up the floor and put down new concrete it's not that difficult or expensive to install wet underfloor heating. The pipes aren't very difficult to lay and it's only a day or  two for a plumber to install the manifold and connect it into the system.

Keeping the house at a reasonable temperature helps a lot with damp issues. These old houses have a fireplace in every room for a reason, the idea being to keep the place warm by burning coal every night. They weren't designed to be freezing. 

The more I look into this subject the more complicated it appears to be but, in short, the answer is if you have solid walls, that are designed to breath, then external insulation is required unless you put a waterproof membrane between the existing wall and the new internal insulation or ventilate that gap (I.e. heat loss). 

There are external breathable insulating renders but they are not as good as the other forms of insulation and are expensive.

Agreed. The problem is that ventilation,  and heat insulation conflict where there is varying amounts moisture in the air, and retrofitting an old building is rarely easy or cheap.

I'v done internal insulation myself, it'll definitely make a difference, and it's not difficult to do but there are pitfalls.

first you'll lose internal space. don't underestimate it, your walls are not straight and plum and in the overall you'll need to round up your measurements to gauge how far in the finished wall will come. if this isn't a big deal, carry on:

it's well worth understanding the principals of moisture, air movement and how damp comes about; it's a massive help to understand what you're trying to achieve so that you can adapt it to your situation.

at it's fundamental basics, you're essentially trying to build a box inside a box, and to prevent air migrating through from the warm side to the cold side of the insulation, and to allow moisture on the cold side of the insulation to leave that space quicker than it can build up (ventilation).

the other fundamental consideration is you need to watch out for are the bits that you don't or can't insulate fully or properly. you might find you have small areas, like around window recesses or the corner where the wall meets the ceiling, where the temp gradient is massively different to everything around it potentially cause local damp problems. this holds true for external insul also where it's cut-out around downpipes, meter-boxes, or anything else that gets in the way of a plain uninterrupted wall-surface. as with everything, the bastard is in the detail.

main thing i'd say is; pay particular attention to the details (edges and interfaces), make every effort to prevent air movement through or past the insulation AND add ventilation. it might be possible that ventilation is unnecessary, but the vapor-barrier and it's installation are not failsafe for the life of the building. say for example you fix a new plug socket into the wall at a later date, if it's not sealed up proper you've just completely undone all your hard work installing a vapor barrier. and excess vent is no harm.

I know it's not what you asked, but just for info I'v added a layer of cork on top of a painted concrete floor as a quick and simple improvement.

misread that the first time. you get pools of water in the summer? Seems a bit odd to me, I'd suggest looking into that to confirm where this water is coming from.  

Diagnose the cause (causes) of damp before doing anything.

There's a million potential causes of damp. Personally I'd start looking at the damp proof course (DPC). For example is it missing, bridged, or right at ground level after bodged paving around it raised the ground level outside. Stuff like that. I'd want to exclude the DPC first (unless there was a smoking gun other cause)

Edit before you say it's a 140 year old cottage it won't have a DPC.. it might (I've seen slate, tarred slate and other materials) and  injected  (look for a row of drill holes low down)

There's a lot of good advice but I'm wondering about ventilation too. Does the window open? Is there a working extractor fan for cooking?

Generally, as you own this house, it's worth taking your time with this to make sure you get it right. It sounds like there's a number of issues to address. Personally, I would pay for an independent survey before commissioning any work.

I'm sure it's fixable.... it's just a question of getting it right the first time, as you imply in your OP..

Poor advice all around there.

DPM's under solid floors within solid wall buildings have a tendency to drive moisture up through the base of the walls.

Injected damp proof courses generally do not work - I regularly provide remedial advice rectifying issues caused or exacerbated by such works.

OP is spot on with the temp gradient. It is almost certainly an issue with intermittent condensation caused by moisture laden air cooling on surfaces that are at or below dew point. What you need to do is maintain steady temps and ventilate.

There are many way to ventilate a building, windows will not always work (dropping temps etc)

I work for a firm of chartered surveyors and head up the heritage side, advise on stuff like this on a daily basis. 

From my limited experience (with our stone built house) this is true. We re-laid our kitchen floor with a DPM, insulation and concrete (working with a builder) and we continue to have damp issues in the walls.

After dumping the builder and doing shit loads of research ourselves we did the other room by digging up concrete floor, putting in drainage, putting down Geo cell insulation (https://www.mikewye.co.uk/product/foam-glass-insulation-aggregate/), then a limecrete screed on top (with underfloor heating). This room is significantly less damp.

We also used internal breathable lime-based insulating plaster on the internal walls.

We considered the whole 'box within a box' idea but we got the idea that this was a bad idea and that (for such an old building anyway) you can never really seal everything with membranes (or guarantee they aren't pierced) so you're likely to end up with interstitial condensation which will cause you problems.

Positive pressure pumps have had good reviews on this here site for damp basements as I recall. Any experience? 

Do you know if internal tanking solves the rising damp? I'm doing the same as OP atm, I've got the walls striped back to brick, my plan was to put two coats of tanking slurry half way up the walls then dot and dab with sticky foam instead of plasterboard adhesive to stop cold bridging, also to lift the boards 2 inches off the floor for ventilation. I'm rebuilding the roof with an 8 inch overhang to future proof it for external insulation .

some light reading for you, hopefully this is helpful.

https://www.heritage-house.org/damp-and-condensation/managing-damp-in-old-b...

Do you have a view on external insulated renders for stone houses? I.e. do they work in keeping the heat in and preventing condensation build up on walls (as I understand it ‘normal’ external insulation could lead to condensation buildup on the insulation which could penetrate back in)?

It seems as though these are the best/only things which would work but don’t seem to be particularly widespread which makes me wonder if they are a bit of a fad!

Cheers, I keep reading conflicting advice about how to solve the problem. I'm trying to get as many opinions as possible. Doing it with boards is a big money saver as I can plaster boards but I can't do all that old school lime plastering. I'm now wondering if I should be putting visqueen under the new concrete floor, it's a nightmare!

Tell that to the last 2 kitchens I've done on my own properties and a pile of other happy customers I've fixed over the years. All I can go on is the training I've had and the successful jobs I've been paid to do as a professional. Many properties I've returned to as the customer has requested additional work due to a successful outcome, never had a complaint in 31 years.

What is it you do at the chartered surveyors again? Make the tea? Only kidding!

Sorry, been out all day and not seen replies. Thanks for all the info, lots to mull over.

In response to a few posts, we're definitely more keen to fix it rather than move on. Damp kitchen aside, we love the house and location and are keen to stay here for a good while.

WRT ventilation, we have a window, an extractor fan on the hob and another separate extractor fan. We're usually pretty good at ventilating the place when we're cooking, certainly better than we've done in previous houses where we haven't had the same damp problems. So more ventilation could be helpful but I don't think it's the root cause.

I'm quite keen on the idea of some underfloor insulation, definitely something to look into. It would be nice to not risk frostbite when I mistakenly wander into the kitchen without slippers in the winter!

Re the pools of water, I'm 90% sure this is just condensation. We only get it when the humidity is high and only in the summer, when the heating isn't on and the temperature differential between the parts of the house that get some sun and the cold, shaded north corner is particularly pronounced. We have a similar issue upstairs in the cold corner of the stairwell to the attic but a decent dehumidifier largely keeps it under control.

In terms of space, it's a big room so I think we'd be OK to lose a bit of it if we ended up with a better and longer lasting result.

It sounds like the best thing to do might well be to get a specialist in who can help diagnose the root cause before we do anything as it seems quite complicated, based on people's comments. A kitchen renovation will be a big job anyway and so I'd rather spend the time and money to get the issues fixed properly and not end up with the same problems cropping up again.

 I'm now wondering if I should be putting visqueen under the new concrete floor, it's a nightmare!

probably yes. capillary action does exist and concrete does suck water up into it. the question is what happens then. you don't have a mortar joints exposed to the open air like you have on a wall.

I'd want the concrete floor well drained beneath, and (imho) cast onto a thick layer of coarse aggregate perhaps even rubble, this'll act as a drainage layer and might potentially even allow air movement depending on external ground level. I realise that there many many different variations of the same theme, but putting a membrane underneath a conc flood is quite universal.

I think that the difficulties that the previous poster was referring to are primarily caused by the chemical dpc exacerbated by floor membrane rather than a floor membrane being categorically bad. remember concrete is quite waterproof itself, it's just not waterproof enough to prevent water and moisture penetrating through it, but is massively more water & vapor tight than any lime based product.

Cheers for the help buddy. My plan for the floor was 6 inches of stone, visqueen, insulation, then concrete so that sounds ok. Still not sure about the walls. Sounds like I need to focus more on breathability and less on damp courses and membranes. 

Unless you're underground I'd leave out the wall tanking, I can't see the benefit or what it's to achieve. 

Not sure by what you mean by not insulate to allow walls to breathe. You can stil insulate and allow walls to breathe, thats the whole box inside box idea. 

Personally I don't like the dot n dab Method of fixing plasterboard to walls, (esp not to an external skin) there's just too much contact area and whatever you use as adhesive will glue up the brick/stonework potentially adversly affecting the whole breathability thing or wicking moisture into the plasterboard. I much prefer wood battens, use treated wood and add a layer of dpm betwee the batten and the wall if it's external skin. Or timber frame standing off the wall if you can afford the space. 

Cheers, yeah I'm hearing bad things about dot and dab, the walls are so unlevel building studwork off the wall will be easier I think.  

The issue is how to allow the new cavity between the drylining and the original wall to breathe. By insulating inside the walls you also prevent heat from the room getting to the original wall, thus increasing the likelihood of condensation within it.  It's far better to insulate outside.

Speaking from experience, dot&dab-fixed plasterboard in a humid area like a kitchen or bathroom will result in condensation circles where the dots and dabs are, even on a cavity wall.

That's because 31 years isn't necessarily long enough to see the effects. what you've done is essentially provide an insulated floor (good), but hide all the other problems (bad).  You're not going to know if someone's had problems after an extended period of time because your customers won't want you back, or they've sold the house to someone else who doesn't know you did the job.

It's been a while since I read up on this, but I was looking into if for both our flat (late 1800 sandstone) and my mum's house (hodge-podge of 1750-1900 construction / hadd-ons and extensions).

Am I correct in thinking that solid sandstone (solid wall) and brick perform better themselves when as dry as possible, and dryness can be achieved by:

1. Preventing outside moisture penetrating (paint, render etc.)
2. Keeping the average temp of the solid wall high to help drive out moisture (damp brick/stone is much more thermally conductive than dry)
3. Minimising any internal moisture condensing on/in the solid wall (I believe external wall insultation can cause the dew point to occur inside the solid wall?)

External insulation will keep the brick/stone inside the insulated envelope, so the average temp will be higher (good) but how will you deal with the dew point being on the interface of the insulation and outside of the SW? Is there a way to trickle vent that interface without then losing all the insulation properties? Or are you better to put a vapour barrier on the inside wall and deal with inside moisture with good ventilation? 

One thing I'm wondering is, if it's summer when the issue occurs, then insulation isn't necessarily going to help much?  Insulation just slows the heat transfer, but if there's no heating in that room then the temperature isn't going to be a lot higher than it is at present. 

I'm a mechanical engineer with a passing interest in this, and by no means expert. If it were me in the OP's situation I'd probably try to find a well respected local passivhaus retorfit or similar low-energy building designer with a proven track record of stone built house retrofits and get some impartial advice before making any decisions.

Might sound nuts, but have you tried just heating that room in summer?

Just googled retrofit projects and found this:   youtube.com/watch?v=bkdJSA0o-3s&

Not the most exciting video but it seems to cover what I was saying to some extent.

Found this pretty interesting: http://luneretrofit.com/diathonite-insulating-lime-plaster-part-1-product-e...

How long do you think it would take for the disasterous effects of my poor choice of methods to show up on a property? 31 years isn't exactly a short period of time.

One of the houses we used to own had the work done in the early 90's, my mother sold up and moved last year with a perfectly dry offshot kitchen.

I will just add my pennyworth. I will let you sort rhe wheat from the chaff re walls. Look up BRE publications. 

Re floor.

The floor, if damp, will act un the same way as a fridge. Water coming up through the floor evaporates if the surface. It requires energy to do that which it takes out if the surroundings so it feels cold because of the evaporation.

Taking up a floor is a massive job. If ut us concrete it is held in compression by the external walls and even witj a jack hammer will not want to come up.

I suggest you asphalt the floor. No moisture or moisture vapour will come through it. You can asphalt the walls as well. Doesn't cost a lot and see if if is ok.just paint it. 

All depends on your budget. 

For what it is worth i live 300m up in a north facing back to back with solid walls, asphalt floor and internally insulated walls with no extra ventilation. No problems. 

So the OP likely has an issue with condensation and your solution is to retrofit a chemical DPC?

How, exactly does that work then?

OP, please describe the damp issue exactly where on the walls, top, bottom, corners of rooms, around the windows etc.

My point is to assess and fix the simple stuff first. Check for leaking drains, gutters, pipes. Areas where moisture could penetrate. Have a look at the materials, plastic paints, OPC? High ground levels? Thermal bridging? Then on to Internal environment monitoring, vapour pressure differentials, ventilation and in some cases material sampling - gravimetrics, carbide etc. Once all that is done then we can start looking at more complex management solutions, which in my opinion are very rarely required and often (but not always) exacerbate the issue by essentially trapping moisture behind impermeable finishes.

You cant recommend such things without at least attempting some diagnostics IMO. 

What do I do at the chartered surveyors...my time is evenly split between advising on condition and remedial specification and advising on listed building planning law, policy and procedure.

At the end of the day, here we all are posting like a pile of internet experts telling each other that our methods are wrong and non of us have even seen the job. I might not even be a builder for all you lot know and you could be a cheese cutter on a Waitrose deli counter.

I'll have a tea with half a sugar and leave the teabag in the brew lad!

Ha!

Watch your Stetson on the way out!

Let's take my previous house as an example. Built around 1895 with the floor joists resting straight on granite sleeper walls with no DPC. Floorboards looked fine, but all the joists had rotted. It's would have looked fine in 1930, but obviously wasn't in the long term.  It's entirely likely that the battening behind your drylining is rotten as a pear, but no-one's going to know until someone tries to replace the kitchen.

...and interstitial condensation in the walls slowly dissolving the mortar holding them together.

Only if it was previously so cold that the dew point was inside the house.

I think it all depends on the resultant temperature of the wall after external insulation - if it's still cold enough to get interstitial condensation them vapour barrier inside is needed.

It's a summer problem because the kitchen is essentially by far the coldest part of the house and all the moisture in the house is condensing in it.  Warmer air carries more moisture so there's lots more to condense out.  It's why Germans don't leave their basement windows open in summer - it stops warm, moist air entering from outside and condensing in the cool basement.  So, your suggestion to heat in summer is valid. Insulation will be useful if it makes the kitchen warmer, but not if it keeps it cooler. As the OP says it's shaded all the time I suspect insulation will help.

After removing the white goods from the kitchen and loading them into the removal van, I was pleased to find the condition of the enclosed spaces were dry and reasonably clean. Other than a bit of dusting the kitchen was in excellent shape with no signs of issues similar to what the OP described.

Who said anything about battening? I certainly didn't as I use a different method using some long hammer in fixings, no doubt you will be familiar with what I'm refering to.

Regardless of what we're discussing, nature will slowly claim our homes back, it's a continous battle to keep on top of it. There is no 'forever fix' to any building so we just use the best methods and materials we can.

This is what insulated lime renders are supposed to fix (for breathable solid walls) but I’m not sure how effective they are, I’ve mentioned them on forums a few times but it’s always met with silence so I guess they are not in widespread use

I think with houses its useful to think about insulation where possible matched with ventilation- for example it may be possible to add a french drain to the outside wall- 

Breathable insulation - there are various options available - recently did some training with these guys;  https://www.thelimecentre.co.uk/contact/ You may also find someone to work with via the green register; https://www.greenregister.org.uk/

Many of these techniques can be straightforward if you have the time available to do them yourselves- or find a local builder to work with- likely will have to research yourself - taking some care over the work will also likely add good results- try and avoid spots where moisture can be trapped- as well as adding insulation/ventilation likely need to upgrade services- typically rewiring/ https://www.niceic.com/householder/find-a-contractor, potentially removing old gas lines (Gas safe Register)  Hope this helps!