Chemical Damp Proof Course questions

On_My_Lonesome

Hi,

My friend is in the process of buying her first house and survey has come back that there is no visible damp proof course on 1 external wall, It says there is no damp recorded on the interior of that wall and advises a chemical DPC.

We both thought for damp proofing the plaster had to be knocked off to a metre or so high but has been told by someone thats quoted that it will be OK not to have ot knocked off just injected from the outside. Is this right or is she storing up problems for further down the line?

Thanks in advance.

Poppy9

We had a chemical damp proof course without hacking off in our first house. Damp patches appeared everywhere after the treatment and for years they fobbed us off with "it's drying out" etc. We had to have one part replastered 3 times as the plaster would just crumble. We were so fed up we sold up and moved!

On_My_Lonesome

Nightmare to have problems like that I will warn her thats a possibility of goes the cheap route.
Thank you.

Poppy9

On_My_Lonesome wrote: »

Nightmare to have problems like that I will warn her thats a possibility of goes the cheap route.
Thank you.

It wasn't the cheap route at the time (25 years ago) but the new approach etc.

Now I would question if a damp proof course is needed. The house we bought was almost 90 years old and pretty solid till they started injecting chemicals into it!

Older, wiser now and have learnt to look at things like gutterings, newly built patios etc. for causing penetrating damp as according to some there is no such thing as rising damp (google it).

On_My_Lonesome

The survey says no visible damp proof course on the wall although moisture tests show no damp inside at all. I guess thats why they have said they can get away without knocking the plaster off as there doesn't seem to be any water inside as yet.

Its all confusing having googled a load of sites say plaster has to be knocked off and then a few say no need. The wall in question also has the stairs on it with no access under the stairs so surveyor wont have been able to check all the way along for moisture if that makes sense.
Think she is going to get a few other companies to have a look and see what they suggest.

Thanks for all your help.

cyclonebri1

I think this may be a case of let it be.

No visible damp course on 1 wall suggests it is visible on the remainder?, but there is no damp detected on that 1 wall.

It could still have one, have blue bricks been used?

I'd live with it and check for damp later as after the wet we have had recently it should be showing if there where a problem.

Leif

I might be stating the obvious, but be careful if a damp proof company is invited around. By all accounts they have a tendency to find damp, and recommend an expensive treatment, which they provide.

I would be inclined to leave it, if there is no sign of damp, including staining and salt deposits. If it aint' broke ...

iamcornholio

No visible damp course does not mean no damp course

Further, if there is no damp after what, how long has the house been up (?), then I can't see why there is a sudden need for any work now. Or in fact why any reputable surveyor would recommend one in absence of any dampness evidence ..... other than for covering his own backside.

Plaster is only removed as part of treatment work for existing dampness, because the damp will have affected the plaster. If the plaster has not got damp, then no need for it to be replaced. However, a solid wall of 230mm thickness, would normally need injecting from both sides

cyclonebri1

iamcornholio wrote: »

However, a solid wall of 230mm thickness, would normally need injecting from both sides

I agree with the rest of this post but this is untrue.
I've used this equipment before and you simply drill halfway and treat this part then drill deeper and treat the 2nd depth, the injector has an inflating bubble that seals the hole in the 1st skin.;)

renovation_man

Although it is possible to install a dpc from one side it is not all about the injection method. As moisture permeates through the structure or the mortar used during the building process, it also depends on what type of base/foundation the house is built on, if it is built on clay you will get rising damp, if it is built on storm ground/boulder clay or rock you probably wont get rising damp.

An important reason for the replastering is that most people render directly to the floor when in fact a 25mm breathing space is left so that damp cannot bridge the wall from the floor through the mortar.

Rising damp injection process has always been questioned, I experimented many years ago and stood several types of bricks in bowls of water covered a third deep in water for several months and not one brick absorbed the water to the top of the brick.

In my own opinion there are better ways of preventing rising damp causing staining or spoiling decor, but if there is no damp reading then there is no damp, so no treatment is required.