Damp proofing

[mo]

Does anyone know what a company that advertises as 'damp proofing' does? What do they put on the walls?

I have seen some paints in B and Q that you put onto the wall (well you put it on as you would paint - not sure what it is - any good?)

[mail]

Dear Mo That is a bit like saying what does a painter do! It can vary from the likes of Lucian Freud to the unqualified man and his dog round the corner who does a bit of slapping on of emulsion.

So a good damp-proofing fim will be a member of his trade association (currently say the PCA [ex bwpda]) with the CSRT (of if it is only damp-proofing the CRDS) and if underground the Structural Water Proofing qualification (cant remember the intials) for all his staff. Addtionally he will be offering the GPI back up insurance for his guarantees. They will state what they do on a prior to contract document. This varies from the basic

1) injection of a chemical or physical dpc in the mortar of the walls 2) associated hacking off of plaster and re rendering

to all sorts of ancillary services such as condensation control, external pipe leaks, external render repairs, underfloor vents, dpms on solid floors and tanking

At the other end of the scale there are firms that rip you off by saying you need to do damp work when you dont and charging 10x the normal rate which is high enough for a good firm. One such firm that a client recently drew to my attention had a BSc director who was very very plausible whose name I cannot reveal but who is operating in the SE of the county. There are about 2000 odd firms in existance and about 200 are members of the PCA.

I have only come accross about 5 that I would let into my house or recommend my clients.

IF you have a damp problem then you need to diagnose it Is it a bridged dpc which is perfectly good? is it lateral penetration? Pipe leak? Condensation? Past RD having left hygrosopic salts?

Paint on walls will only work in a tanking situation and I doubt very much any supplied as DIY at B and Q would be appropriate for true lateral dampness Rising dampness is not cured by paint!

If you have not the skills to determine this and you can find a firm that is a) a FULL member of the PCA b) the surveyor has CSRT c) they offfer GPI insurance then there is a 60% or better chance of you getting an accurate diagnosis on a free survey but be aware that they are there to sell y ou dpc if they possibly can. By that I mean there will have to be evidence of rising damp but it may not be so bad as to need the full works and it may be simple bridging so beware of the salesman and ensure you understand precisely what he is saying and that it makes sense. If he cannot but tries to say "in my experience" etc - just show him the door and let me know (out of interest) the name of his firm. I am happy to look at photos and comment on our ususal pro bono terms! Chris G

[Phil L]

It's what they put *in* the walls that stops the damp - they usually inject a silicone based waterproofing liquid into a course of bricks along the perimeter of the house, usually about floor level, then hack off and replaster the bottom metre of plaster on all downstairs walls, using various damproofing chemical admixtures in the cement render.

If your damp problem is higher than a metre from the ground, it's not rising damp and a chemical DPC will not cure it.

no, this is akin to buttering the upper side of a slice of bread which is floating in a bowl of soup.

[mo]

The damp isn't rising - as you put it

It only affects the upstairs rooms and comes from the ceiling and from near the windows (which are double glazed)

i mean its not a major problem whereby the water is pouring in but in some places the wallpaper has gone a bit mank/dark because of the dampness.

what do you think?

[Cod Roe]

The roof and window ledges leak?

[Phil L]

I haven't seen it but it can only be one of two things now that we have eliminated rising damp.

1) condensation 2) penetrating damp

if it's 1, then your loft/walls may require insulation, or you may need more heat and/or ventilation in order to raise the temperature of the surfaces or to add airflow. if it's 2 then it needs fixing, either the window isn't sealed outside or the gutter is leaking above the window

[mo]

someone suggested to my sister it was condensation but i didnt believe it!

its happening in all 4 rooms upstairs tho... ?

[mail]

Mo It may well be condensation can be characterised with the presence of a black mould such as Aspergillus niger or if no mould then the characteristic curved shape of the condensation as it approaches a corner which is a cold bridge

There are on the marked "condensation" tabs which test for this

Chris

[Stuart Noble]

Condensation is normally a winter only problem.

[mo]

What are these tabs?

Right in my room personally I get it on the wall facing the outside. I get patches near the floor which seem wet and then bit of wallpaper have gone dark in seemingly random areas.

Can someone define rising damp? Am I right in thinking it can only rise from the floor? lol

[mail]

Dear Mo It is the migration of hygroscopic salts from the ground up the mortar of the wall (not necessarily the stones or bricks which may or may not support such migration) and with the evaporation of the solvent (water) the salts are deposited in the plaster which itself shows hygroscopic properties. I can exceptionally go up 1.5 m but that is unusual and it is normally limited to 1 m from the ground.

I will look up when I have a moment the tabs but try googling Safeguard Chemicals and ask them if they sell them.

Chris

[mo]

-

Thanks very much for your details reply - i will check out that company.

I will also try to take soem pictures in the morning (when it is at its worst!)

[Clot]

We live in an early 1980's house which we've had from new. I have only had emulsion on the walls throughout that time. We also suffered from limited stain/ moldy marks on parts of the ceilings of the northfacing bedrooms (eaves and behind freestanding wardrobes, etc. having little air circulation) and on the east and north facing walls of the northern/ eastern bedrooms, even though all the south facing windows were dg and north facing secondary (I know this is not the best but the builder put in dg to the south rear of of the house to comply with thermal standards because putting on the north facing front would have been considerably more expensisive - small Georgian panes.) We had young kids in the 80's and I guessed it was related to the generation of moisture from the bathroom. Put a dehumidifier on the landing and initially removed copious amounts of water which tailed off though did not completely stop condensation on the secondary glazed northern windows. Where was this water coming from?

I moved the dehumidifier to the kitchen - bingo the largest source of water in the house. Pretty much solved the problem for us.

HTH