Damp? Please help!

[samantha08]

Hiya, I'm in desperate need of some advice about a possible damp problem in my house. I'm losing sleep- please help me!
You'll gather i have no idea of the technical terminology so please excuse my ignorance.
Bought and renovated the house in 2000. House was built in 1850. We had the house damp proofed- it was tanked at the back and injected everywhere else. We had no problems at all until last summer.

We started to get greeny coloured patches coming through the wallpaper on the front wall. This colouring came along with what looks like salt and it just spread all over the wall- not in one big piece but pretty randomly, up to approx 1 metre from the floor. At the same time the laminate flooring in the same area started to lift. When we stripped the wall it was covered in green patches with the salty stuff.

To cut a long stort short, it just got worse and worse and the laminate is obviously rotten. We got a builder to come and have a look and he said that the damp course had failed. We have a 30 yr guarentee on the damp course and got the builder who did the damp course to look and he said he'd come and do it again but didnt seem totally convinced this was the problem.

Then, about a month ago, the pavement at the front of the house collapsed and it looked as though there was a burst pipe as water was squelching from under the concrete when it was stood on. Sure enough, the water board inspected it and it was pouring water out. Its now been fixed and the home insurance is going to cover repairs.

So, heres where i'm in need of some help.
Would it be possible for the water from the burst pipe to have found its way to other areas of the room apart from the front? I'm asking this because other areas of the room seem to have been affected and am worried that it is the damp course as well. Also, the front wall is really badly affected by that salt and i'm wondering if this will stop now the leak has been fixed. (thats what the insurance man said would happen).

Sorry that was so long and rambling, i'd really appreciate any help or opinions.

 

[Joe Malone]

Hi Sam,

This sounds like a complicated problem but the simple answer to the burst water main issue is that yes it will cause damp. Even if it's just by virtue of the fact that it's raised the local water table, high water tables are a huge factor in rising damp problems. I have to say that I think you've made some serious errors in the original renovation work. I would only ever chemically inject buildings of this age as an absolute last resort and damp membranes are an absolute no. Buildings of this age are meant to 'breathe'. They do this because they're constructed using permeable building materials such as lime mortar. Using modern materials, stops them from breathing and you'll eventually have damp problems. Sure modern chemical injection techniques will hold back the damp for a while but this is more to do with the impermeable renovating plasters that are used in the second stage of treatment. You need to tackle the damp issues at source and what you've done is temporarily covered them up. This is why the system has failed so soon; chances are that you never had a rising damp problem in the first place. I make this comment on the assumption that the burst water main occurred after the original damp works were carried out. I'm happy to talk this through with you if you'd like to drop me an e-mail directly to *******

Joe

 

[JerryM]

don't get worried about this. just take you time and you will get it sorted.

Would it be possible for the water from the burst pipe to have found its way to other areas of the room apart from the front

Yes. the dpc is like a line that goes around the house at a set height (normally 150mm above ground). some house have a visible dpc others not. what's important is that if water rises above this line it will bridge the dpc. if it's a cavity wall then the cavity will flood and water will then start to enter the inner wall. if it's a single leaf then the water can only travel by moving along from brick to brick and will therefore move slowly.

if you have single brick side walls and a cavity front wall then i would expect you to have lots of damp on the front wall, a lot of damp on the side walls at the front but quickly reducing to very little moving towards the back of the house.

the front wall is really badly affected by that salt and i'm wondering if this will stop now the leak has been fixed.

No. unfortunately the salts in the soil are what's called hydroscopic and these have moved from the soil into you brickwork (above the dpc) and into the wall plaster. these salts will continue to absorb moisture from wherever they can. as the leak has been fixed and as the installed dpc was good upto the recent event then it can be expected that these bricks will dry slowly and will no longer feed the salts in the plaster. however condensation in the room air will. option normally would be wait and see what the extent of the problem actually going fwd is going to be. i feel the front wall at least will need replastering.

given this is the subject of an insurance claim then i believe you should raise this with them now to ideally get the plaster replaced now whilst they are doing the rest of the work.

the render on the walls is also likely to need replacing. as part of the "house damp proofing" ie after the injection the walls should have been rendered with a waterproofer mortar to retain any salts in the brickwork above the installed dpc moving into the new plaster. it appears this render may not have been good enough for whatever reason.

in summary get you insurance company to cover for the full repair to the buildings damp proofing by including re plastering and rendering. you will probably need to get a survey completed by the original damp proofer or somebody else to provide evidence that this work is necessary to return the house to its original condition ie before the leak. if you get someone new then best to get at least 2 or 3 quotes "statements" of what work needs doing (the insurance company may do this for you).

 

[Joe Malone]

Unfortunately I find myself in the position of having to deconstruct the advice that Jerry has provided. It's standard DPC industry advice and wholly inappropriate for a building built in 1850.

Thomas, Control of Damp in Old Buildings (1992) states: A common way of coping with rising damp is to strip the internal plaster, and replace it with a waterproof render upto and well above the tide mark. This tends to force the water further up the walls and usually recreates the same problems at a higher level. This method is not recommended.

Ashurst, Practical Building Conservation (1988) states: The treatment includes replastering with a strong impermeable, sand and cement render. By any standards this is an inappropriate measure for older properties built with lime mortar, and will interfere with the subsequent diagnosis and treatment of any genuine dampness problem which may exist.

A building constructed in 1850 is unlikely to have a physical dpc installed. In such cases you control rising damp by having adequate wall base ventilation. External ground levels need to be 200mm below internal finished floor level to ensure this happens. These standards were laid down in the Liverpool Building Act of 1842 and continue to be relevant today.

Water does not only travel from brick to brick; in fact the major moisture pathway for rising damp is the mortar course and moisture will travel up through the mortar perps long before its travelled up through the brick. Again this needn't be a problem so long as you continue to use hydraulic lime mortars for any repointing work. Lime mortar 'breathes' and allows the moisture to evaporate as quick as it rises. Using the correct building materials is absolutely key to controlling any dampness problems that you may have!

They are not 'hydroscopic' salts as Jerry mentions, they are hygroscopic salts ans needn't necessarily eminate from ground moisture. Many hygroscopic salts are present in building materials; for instance calcium sulphate which is present in plaster quite often dissolves out in the presence of moisture and migrates to the surface, this doesn't mean that you have a rising damp problem.

It would appear that you've already followed similar advice to that given by Jerry and unsurprisingly you've had a re-occurence of the damp problems. You need to treat the problem at source and not carry out works that will do nothing more than dam in the damp and cause you problems further down the line. The DPC industry have a 'one piece of advice fits all' approach and do not recognise specific requirements relating to old and historic properties because that would mean turning away a proportion of their business.

Joe

 

[JerryM]

have been giving some more thought and the mechanism "way" in which the water has moved from the leak to the walls is not sitting right.

i think something else is wrong and probably needs fixing. the survey (that you need to have) should focus on identifying the cause and what i am saying is you need to give this particular consideration.

why it's not sitting right is for bridging of the chemical dpc to have occurred one or more of the following must have occurred (more easily understood by drawing a simple picture of the cross section through your front wall, adding on the dpc posn's along with the internal/external floor levels).

1) the water has travelled underneath (or through) the outer leaf and entered the cavity with the level rising above the dpc level - typ 150 mm water rise which is pretty unlikely (there would have had to be captive water under mains pressure)
2) the water travelled under the foundations and reached the ground floor slab (assumes no wooden floor). if this is higher than the internal dpc then the bridging could occur. possible
3) same as 2 but internal dpc higher than concrete floor but plaster in contact with the concrete floor allowing bridging. possible
4) as 1 but debris exists in the cavity allowing bridging between outer & inner leaf above the dpc levels. possible.

why i list this extra detail is that it's crucial to find the cause or take appropriate action. given just the info from the observations my gut feeling would be to tank the walls at the time the plaster/render work is undertaken.

given what you say about the pavement collapse i also think you need to be certain that the foundations have not been affected (again the survey).

 

[Joe Malone]

Hmmm, would you not agree that given the age of the property (1850) it's unlikely to have any foundations. My guess is it's built on a stone or brick plinth sat on compacted earth.

 

[JohnD]

good point

and I imagine lime mortar washed away by the leak, to give gaps and loose brickwork (but very clean) and maybe red worms too.

I sense a good insurance claim.

 

[JerryM]

don't be alarmed about the foundation suggestion. it’s difficult to judge without seeing if it is a problem or not but it’s worth highlighting all possibilities if only to be discounted.

To me it reinforces the need for a proper survey for peace of mind.

i have had a lean-to kitchen on the back of a terrace which subsided due to a cracked rain water drain. early diagnosis (if there is a problem and there may not be) will mitigate the extent of damage which would otherwise potentially occur over time.