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Damp Proofing

Help! extensive damp, treatment with chemical injection versus plastic membrane

Hey there, i am looking for some advice!

My house has extensive rising damp in most of the lower house. I have had 2 different quotes;

Quote 1 advocates chemical injection to solve the problem. This has already failed on this house in the past. They said that plaster would need to come off the wall, then the walls would be replastered immediately.

Quote 2 advocates the use of plastic membranes. They suggest again taking the plaster of the walls and after a few weeks of letting the bricks dry out to replaster the walls.

I am really unsure what the best course of action is, and as I am meeting these builders myself and knnow little of the subject, I really dont want to be ripped off of for the wrong method to be used.

Please help!

Nikki x

5 Answers from MyBuilder Damp Proofing Specialists

Best Answer

best solution,is to take over lower part of plasterwork,re render with waterproofer involved,this will not allow damp to penatrate outwards into your rooms,injection is not a good idea in older houses as prick work is in not of a good standard,ie cement joints are not always good,so a damp course has problems running from one prick to the next,use sbr in the render,then tank,another waterproofing system,let to dry and then re plaster,long winded,but works.


Answered 31st May 2011

Both methods are effective, the injection method has come on alot in the fluid what is used today to what it used to be. Both methods are going create mess as both require the plaster to be chopped off to a meter high, so one thing you need to look at is are you prepared to look at bare brick for 2-3 weeks whilst it dries and in some cases it can take longer.I used to work for a company that specialised in damp-proofing and to be honest the plastic membrane was only used in the most extreme cases. Infact in the two years I worked there i only used it twice and that was in a basement in a converted mansion that had water literally covering the walls! The most commonley used method is to chop off the plaster to a meter high and inject, and in some circumstances tanking is applied to the walls to seal them. There is also another method to solve the problem which is to use plasterboard. My sister had a bad damp problem in her house which was an end terrace, I started by chopping off injecting and tanking and that failed within a month. So i ended up using insulated plasterboard and skim to the walls and this was around 3 years ago and there is no sign of any problems coming back. I hope this helps, if you need to know more then please feel free to ask. Thanks, Michael


Answered 31st May 2011

Hi Nikki

Chemical DPC is the usual choice for walls that are not earth retaining! Well you can DPC as long as its above the outside level by 150mm,so are your walls earth retaining?
I agree with the first quote in the matter of the DPC and replastering go hand in hand as once you have rising damp and it has bled through the plaster you will see tide marks at the highest point,this will be a salt band and this means the plaster is now contaminated and as a rule we would remove the old plaster to 300mm above last signs of moisture/salt marks.

Cavity Drainage Systems/Membrane is a great choice aswell.But only really needed if your walls are earth retaining or or have raised area`s against your property.
With the Membrane system you can strip old plaster off and fit the Membrane the same day and either use a mesh type Membrane and plaster straight on top or use a Membrane that you can Batten and plasterboard then skim/finish plaster.

If you have doubts take the two Quotes offered and tell them you will be in touch as you have a third Remedial Treatments company to investigate.
Either call out a third company offering a free Survey/Estimation of works or look to a company on My Builder who are local to you that can offer a FREE Survey.

Good luck and dont let them pressure you into anything.
Hope this was of some help.

Scott Cannon.
Cannon Preservation.

Can i just add Rising damp can and will travel alot higher than 1 metre if allowed and its all to do with the type of conditions/brickwork.The "capillary action " which is a discription of how the moisture moves up! does so through rising up through small type flutes in the brick and if the flutes/passage is not blocked and clear the damp moves up like being sucked up by a straw/wick.

The DPC chemical or Cream fills the mortar joint and masks and lines the tubular flutes in the bricks and by doing this the water has no grasp to travel upwards.


Answered 1st Jun 2011

Hi Nikki

Both Methods are commonly used to stop damp.

Rising damp can only rise 1m, after this gravity stops it rising. if you have damp much higher than 1m your problem is not with rising damp. (just a thought after your mentioned that the house has suffered with damp even after having the injection of chemicals)

the way chemical injection works is by filling the brickwork/stonework with silicone preventing it from absorbing water this however isnt always effective if your pointing between said stonework/brickwork isnt waterrproof as damp can easily track up there.

the tanking system is commonly used in basements and such (iunderround propertys) if your property is half underground or ground levels are higher than your existing DPC this is most likely the bestsolution although both are proven to work.

not the most helpful message will help you understand a little more possible :)


Answered 31st May 2011


I personally have found the injection process to be very effective if done correctly, and injection damp coursing only last 20 years or so.

There is a new injection product called DRY ZONE, which is a cream instead of a fluid and is a much tidier process. Again the plaster would need to be removed up to a meter high or however high depending on bad the damp is, then injected with the cream and given time to dry, at least one week.

At this point there is a choice to be made. You can paint onto the brickwork a liquid dpm. A couple of coats would be needed. This process is used to waterproof walls in a cellar conversion.

Next a sand and cement render is applied with a salt inhibitor such as RENDERPEL (but there are many different ones on the market that are suitable.) This render is the re plastered with a normal plaster to a suitable finish and given time to dry out thoroughly.

I hope this has helped you.



Answered 31st May 2011

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