damp - inject vs tank vs dry line

[edgarina]

Hi Everyone,

I own and rent a 1920's terraced house with some damp issues and want to do more than repaint with damp seal again!

After some reading I remain a little confused. The damp is ostensibly rising from the adjoining walls with the houses at each side. I realise 'rising damp' may not be the correct diagnosis and that its a little more complex than that. Having takne some plaster off, as it was well on its way anyway I find the lowest bricks have previously been injected but could have been decades ago. Some of the revealed brickwork has the typical white fluffy salt deposits and some is blackened and slightly moist to the touch. The floor is concrete which is probably the cause of the problem as I don't think this was the original constuction. Its a middle downstrairs bedroom.

Certainly don't have the money to dig out the floor and replace with a suspended floor. For context the house is only worth 70k. I have read that tanking will work fine for a while probably several years but will force the moisture else where eventually. I have read injecting is also probably just sealing an area, again failing in the future and or spreading it else where. I also don't know how effective injecting is if its already been done in the past.

I read that the damp is probably being forced to the base of the wall by the impermiable concerete slab and no ventilation or other place for it to go, made worse by condensation. I have read that if the water/damp has a place to evaperate safely the problem can be as near as solved. I gather dry lining with a timber wall lining batoned against the wall so its not against the wet brick work and some vents installed will allow safe evaperation. This technique being the origins of the T&G wood lining to a dado rail.

Does any of this make sense or am I talking crap?

If dry lining is the best move should I replaster the now bare brick with normal plaster, remembering its a little wet, leave unplastered and just dry line from the brick work or what?

Unfortunatelky my time frame is very small as the students are returning and I only a have a couple of weeks to sort.

Thanks for the help,

 

[^woody^]

You seem to have done quite a bit of reading, but you have to be careful not to misdiagnose the problem and most appropriate remedial work.

You need to identify exactly what is causing the dampness and be sure that that can't be eliminated.

A concrete floor is not going to be the cause of the problem as you state - concrete is not impermeable.

If the damp is on party walls, then the neighbours must also have a problem? Any form of dry-lining or tanking may not be suitable

I'd suggest putting down the books and getting someone experienced to have a look at it

 

[edgarina]

Fait comment woody, yes am trying to line up some 'experts' for comment next week but again from reading (sorry i'm a researcher thats what I do) I gather if you get a damp proofing injector expert in 9 times out of 10 they will, surprise surprise, recommend injecting guarenteeing it wont affect the area again but of course not guarenteeing it won't affect an adjacent area. Sorry extreeme cynacysm also helps the research..

The party wall is an issue, I don't know if that year of terrace house will have a cavity gap or not. Next door I think is also rented or similar and to give you an idea the back yard is about 2ft high in rotting rubbish and weeds growing from the dramatically failed concrete out there. Constructive communication is not likely and to be frank as long as the damp doesn't come in my direction Its hard to worry too much about where else it will go.

As a relatively cheap fix I can do a lot of myself I am leaning towards some batons against the brickwork, with plastic layer to stop them rotting, and then either T&G which will naturally breath and I can do entirely myself or some plaster board with some vents that can then be skimmed, not by me. Easy to remove and re-think (re-use in future) if It goes south at a later date. Probably treat the T&G so it also resists rotting. This will certainly be less than the £50 square meter tanking is may be.

Very much open to any and all comments however.

 

[mointainwalker]

You can also get independent damp-specialists who don't undertake treatment and therefore are not seeking to "create" a problem: those you do have to pay for.

 

[gregers]

as said if its on the party wall then next door may also have the problem?

why not remove the plaster,black jack them last coat sanded then sand cement coat that should do the trick.

 

[Blagard]

I worked in local authority for five years dealing with improvements to old housing stock. One of the big problems was the common incidence of rising damp and the idea then was to encourage with the provision of grants, damp proofing to all walls to all properties without a DPC. The problem area of party walls means you can only safely inject on half of a 9" party wall, so ideally get adjoining properties done to complete the task. By and large I think it was successful with after problems arising from crap installers, DPC bridging or incorrect replastering.

You can't really do much about your neighbours side of the party wall. If the DPC was done properly there should be a warranty for it (for what ever it might be worth!). One basic principle is you do not plaster over an injected DPC. The very act bridges it. You do not use a gypsum based undercoat in the remedial plaster above in the commonly affected 1m high band. It acts like a damp wick. You need one of the renovation plasters. If you have to, you need to use a deep skirting board in front of the injection course to avoid bridging it.

Slapping on some tanking medium might help on some some properties. Drylining simply removes your plaster fom direct contact with the source of the dampness - your wall. But you loose a bit of room size and no longer have those nice solid walls to fix shelves directly to.

I also know that far too many DPC / timber treatment companies will find any excuse to sell their product. - I only know one or two locally that I remotely trust for a decent report.

To get back on line quickly I would replaster above the DPC as necessary using a renovation plaster, fit appropriate skirting boards and see how you go. I think your post indicates you don't have the time for surveys etc this year!

 

[edgarina]

Thanks for the replies. Yes there is no time for an independent opinion or I will lose the returning students. Good point about the high skirting this had crossed my mind. In places the replastering after the injecting, when ever this was done, did go below the line of the injected course, to the floor almost, so as you say basically poor quality work in this kind of housing stock where selling prices are so low the percentage costs of good quality inclusive renovations are very large and so never happen. With these houses changing hands frequently each owner repeats the cycle.

I will try and do a good job as its a very long term investment for me and see how we go.