Injecting a DPC

[Penners]

Not me. I'm definitely in the highly sceptical camp.

 

[Moo]

... the wall is surrounded by a cement floor. The bottom few courses are affected.

I rest my case, m'lud.

 

[Stephen]

There are in fact two issues here, perhaps interrelated, but need to be considered separately: the here and now 'what to do?' and the 'what if?' situation relating to future mortgage valuer inspections.

Regarding the former it seems to have been well covered already. Irreversible treatments should be a last resort (regardless of whether you think they do or don't really work). In my experience the vast majority of such situations can be resolved without reaching the last resort. If you think about getting the property back to functioning as it did before the problem arose and reversing those works (e.g. heightened ground level being lowered, impermeable renders being removed, etc) this should resolve much if not all of the problem. Sometimes it is not possible or practical (or economic) to reverse works (e.g. taking up a concrete floor) and other solutions may need to be found if it transpires that such matters are critical to the final solution (concrete floors may not create a problem if the water table is not high and the ground under the building drains freely so that the building is not sat in water). Even if these works do not resolve the problem it may be that other solutions focused on moisture management would be preferable (e.g. use of a drained membrane system). Failing all that if a DPC is really needed think about having a physical one inserted as this is the only certain way of creating a barrier to rising damp in a wall. You also have to consider that just because a moisture meter gives a reading it does not follow that you actually have a problem that requires work. That moisture recorded could be a temporary reading (e.g. from a leaking gutter splashing the wall), or it could be that there are no vulnerable materials (i.e. timber) nearby and/or it is not causing damage to decor and therefore the level of moisture is 'acceptable'. It is far too easy to jump to a conclusion that a 'treatment' is required; for the professionals/builders, etc it is also often a lazy conclusion in that they cannot be bothered to think it through and work it out properly.

On to the other matter though - that of mortgage valuations.

Mortgage valuers work under tight constraints that often includes what they must say in certain situations. Because of the nature of what they are doing they are not there to undertake a detailed assessment of condition. They merely identify potential problems and decide whether to ask for further reports. Quite often the words they use are pre-determined by the company so that the office clerks know how to then process the valuation. Sometimes the guidance is as simplistic as - if the moisture meter gives a reading of over xx% recommend further inspection by xxx. There is often no leeway for them. I am not here to act as an apologist for them, merely pointing out what happens. The same applies to cracks and other defects.

The problem comes when you look at who they are told to recommend to undertake the next inspection - the high street specialists. Some are good and some are ... as has been discussed here before. The reality is however that often those high street specialists will do no more in terms of investigation than the mortgage valuer (i.e. using a meter on the surface) before deciding that a treatment is necessary. The mortgage company will take their word for it and declare that they will not issue the mortgage without either a condition or retention relating to those works.

Mortgage companies do not (as far as I know) have anything that says the properties must have a DPC, but what I have described above is usually the scenario that leads to the mortgage company declaring that an injected DPC is necessary.

There are several possible ways to deal with this.
1) if a condition (not a retention) agree to it, but seek separate advice and more often than not you will not be undertaking any work. Keep a record of the reports and advice obtained. If they ever ask about compliance with the condition then explain what was done and how resolved. In reality they rarely check up on conditions. Bear in mind (from a purely mercenary point of view) that if the mortgage company are saying that the property needs work (even if it doesn't) it gives the purchaser some negotiating power.
2) if a retention get second or third opinions from those that really do know what they are doing and/or undertake more thorough assessment and testing if necessary. Then argue it out. Send them copies of any report that gives a different opinion, etc. Again however bear in mind that a retention is quite a powerful negotiating tool for the purchaser.
3) if the property is listed point out that such work probably requires listed building consent and point them to the various publications (SPAB, EH, etc) that clearly state that such treatment is not appropriate for historic buildings. You could go as far as contacting the CO for the Local Authority and getting an opinion as to whether he/she will require consent for such work. Furthermore, if the work is undertaken without consent it might be considered a contravention of the law and criminal prosecution may follow - does the mortgage company want to get immersed in a legal battle, if they insist on a treatment that may not be consented.
4) threaten to take your business elsewhere.

This is a rather quickly produced reply and it does not necessarily cover all eventualities, but hopefully it is helpful.

The important thing is to do what is right in terms of the here and now. If a 'problem' is identified in future deal with it then. Whatever you do though keep good records before during and after the work because this could prove useful in future.

Hope this is of some help.

Stephen

 

[Zebra]

Thank you Stephen that is helpful and a very thorough reply.

I don't have a mortgage, and am doing the house up to live in not to sell, so the mortgage issue is not something I'm really worried about. The problem is only having damp walls.

So nobody reckons on the electro-osmotic thingys, no?

it could be that there are no vulnerable materials (i.e. timber) nearby and/or it is not causing damage to decor and therefore the level of moisture is 'acceptable'

What would you finish the walls with so that damp didn't present a problem? At the moment, all the walls are stripped back to bare brick so there isn't a problem, up it comes and evaporates away. But I have to put some sort of internal insulation on the external walls, and won't that trap the damp against the wall, or its insulating value be affected by the damp? Won't I get tide marks on the plaster?

Incidentally, maybe a daft question, how do you insert a physical damp proof course right the way through a solid 9" wall with the house sitting on it?

So perhaps where I have rising damp on bare internal walls with no render, that must mean the only remaining option is to dig up the cement floor. Hmmm. I wonder what was on the floor when the building was functioning as originally intended... And how would I make a join between a "breathable" floor and the new front extension where they are bound to put a damp membrane... Hmmm :?

 

[Keithj]

When the bodged work on our Tudor house was being repaired, we found some of that "injected damp course" stuff. It was a joke - little chunks of some sort of plastic/resin about the size of my thumb, in holes drilled in the walls about a foot apart, with plastic covers over them. They clearly fulfilled no useful function whatever.

The real problem was that the bodger had smothered everything with concrete, hence accelerating the rotting of the sole plates. That cost us close to £30k to repair.

 

[Matt Green]

So nobody reckons on the electro-osmotic thingys, no?

My ex-boss has quite a bit to say about them. Not much of which is polite. Shall we say that searches for evidence that they have any effect when installed without cement render prove difficult?

Incidentally, maybe a daft question, how do you insert a physical damp proof course right the way through a solid 9" wall with the house sitting on it?

It's not that draft- you do it exactly how you would expect: angle grinder, dpm and and mortar. Gives you a strange unsettling feeling doesn't it? There are companies that will do that for you though.

So perhaps where I have rising damp on bare internal walls with no render, that must mean the only remaining option is to dig up the cement floor. Hmmm. I wonder what was on the floor when the building was functioning as originally intended... And how would I make a join between a "breathable" floor and the new front extension where they are bound to put a damp membrane... Hmmm :?

Ah, now you are getting to the grist of the problem. It depends how far you want to go to make your building work as intended. It gets a bit serious when you get to the rip-up-the-concrete-floors part of the operation.

I would be inclined to dry line the wall keeping the battens isolated from the masonry and as far off the floor as possible.


M.

 

[Stephen]

I was going to suggest some form of dry lining as well as this results in a dry surface but allows the water to move through the fabric as it always has. Depending on how much damp there is you might need to consider providing a form of drainage for the water.

The floor is more difficult and it depends if it really is causing a problem. The range of options are - do nothing to take it up and replace. Between the two is something I have seen used on a couple of occasions where a breathable perimeter strip is formed and/or a series of holes through the concrete that are then filled with a lime mortar mix. This avoids having to take up the whole thing, whilst creating a degree of breathability.

Stephen

 

[MdB]

Between the two is something I have seen used on a couple of occasions where a breathable perimeter strip is formed and/or a series of holes through the concrete that are then filled with a lime mortar mix. This avoids having to take up the whole thing, whilst creating a degree of breathability.

We have done approximately this. The wall is considerably drier but the very base and the lime strip is still slightly damp. In our case this is due to the house being on clay and a very high water table. In this situation, no amount of evaporation is going to dry the moisture out completely. The outside ground levels are already 200mm lower than floor level but I'm going to see if this can be improved on further and do other things to lower the ground water level.

 

[Zebra]

My ex-boss has quite a bit to say about them. Not much of which is polite. Shall we say that searches for evidence that they have any effect when installed without cement render prove difficult?

I see. I'm sure you are right. I was just going on the evidence of some friends of my Mum's, who say they have one and have "never had any problems with it". I was just thinking I might buy a bit and stick it in - it's not anywhere near as invasive as an injected cream, and anyway it's reversible - and see if it does make any difference...

I would be inclined to dry line the wall keeping the battens isolated from the masonry and as far off the floor as possible.

I was going to suggest some form of dry lining as well as this results in a dry surface but allows the water to move through the fabric as it always has. Depending on how much damp there is you might need to consider providing a form of drainage for the water.

So you'd have a barrier just behind the battens, or behind the whole thing? Again, would any insulation between the battens trap the damp against the wall, or its insulating value be affected by the damp? Any ideas on what type might be best? Breathable or non-breathable? I only have a 70-80mm depth I can afford, otherwise only skinny people will get up the stairs!!
I don't think there's that much water to need drainage, but then again, won't know til I've got my French drain dug, and won't know til it's winter!

The floor is more difficult and it depends if it really is causing a problem. The range of options are - do nothing to take it up and replace. Between the two is something I have seen used on a couple of occasions where a breathable perimeter strip is formed and/or a series of holes through the concrete that are then filled with a lime mortar mix. This avoids having to take up the whole thing, whilst creating a degree of breathability.

Yes I've thought about this too. I've dug a bit of a strip, through the cement down to the hardcore, but not filled it with anything yet. Lime mortar is OK, not limecrete? This is good, as I've been making lots of lime mortar!

We have done approximately this. The wall is considerably drier but the very base and the lime strip is still slightly damp.

Mind if I ask what you have got on your walls internally, and also what floor covering you have over the lime strip?

Thanks all for your advice.

 

[Flyfisher]

We have done approximately this. The wall is considerably drier but the very base and the lime strip is still slightly damp. In our case this is due to the house being on clay and a very high water table. In this situation, no amount of evaporation is going to dry the moisture out completely.

My understanding is that breathability doesn't really eliminate moisture, it's more a case that it enables any moisture to evaporate quickly so that there is no build-up to the sort of levels we recognise as 'damp'. I've probably bored eveyone half to death with the rubber glove analogy but here goes again; put a rubber glove on your hand and within minutes it will be all sweaty and damp, yet the other hand will remain completely dry - even though it's giving off just as much moisture as the rubber-encapsulated one. If the moisture can evaporate there will be no build-up of damp.

One of our rooms has a pamment floor laid directly on the ground. It used to be covered with a carpet and, when lifted, the carpet was soggy to the touch and the tiles were visibly damp. Within days the tiles visibly dried out and now appear to be completely dry to the touch - yet all we did was lift the carpet, thus allowing the floor to breathe, thus allowing the 'damp' (which must presumably still be there) to evaporate, just like the ungloved hand, leaving a dry floor.

I guess the trick is to have more 'outgoing breathability' than 'incoming moisture' if that makes any sense?

 

[Penners]

I've probably bored eveyone half to death with the rubber glove analogy but here goes again; put a rubber glove on your hand and within minutes it will be all sweaty and damp, yet the other hand will remain completely dry - even though it's giving off just as much moisture as the rubber-encapsulated one. If the moisture can evaporate there will be no build-up of damp

I don't think that analogy could ever be regarded as boring. It's an excellent one and bears frequent reiteration.

 

[JoceAndChris]

I don't think I've read that before anyway - an excellent description and one I'll try to remember when explaining this to friends who are frightened by damp.