Damp Advice

[Buller]

Hi all, have been reading the numerous posts relating to rising/penetrating damp and havent found the answer to my problem so thought id put it to you all direct! The house is a 1900 end terrace with solid walls.

When i purchased the property i was told by the surveyor that there was damp present. I employed a contractor to carry out the chemical damp course installation. When carrying out the works he hacked of the existing plaster (soft sand based mix) to varying heights from 500mm to 1200mm. Once complete he rendered the walls with a sand/retarder/cement mix before skimming with multifinish. He recommended to allow the walls 9 months to dry out before final decoration. 12 months on and their is still moisture present on the wall. The moisture is only visiable in those area where he took the plaster off to 500-600mm and it appears in horizontal sections for 200-300mm above his new plasterwork.

I spoke to him today and he has said that the old plaster is affected by salts and was drawing moisture through the wall and therefore needs hacking off and replacing. Apparently if i simply remove the affected area and re-render (he was strongly against limelite) then the problem will cease. However if the old plaster was affected shouldnt all of my wall with the existing plaster show damp signs not just the areas immediate from where he has worked.

Really i believe that as i employed him to remedy my damp situation he should off hacked off enough to sufficently eradicate the problem. Although if the hacking off will cure the issue i will probably do this myself to avoid the hastle of him returning. But i am worried that if i remove the 300mm section affected the damp will just appear above that section???

He also went down the lines that the damp could be penetrating through the walls due to mortar issues/spalling, although surely this would be visiable in other areas?

 

[JerryM]

i would think twice about injecting (or whatever method of putting in a chemical dpc) into solid walls unless they are a single leaf of brick (they are tricky due to bridging). i most probably would have tanked it.

we are where we are though. the max height of rising damp is 1.3m above ground. the normal knock off height is 1m. all walls should have been knocked off to 1m in the 1st place. the normal allowed dry out time is 1 month per inch of wall/brick. i normally work on 6 months but the house must be ventilated (ie an upper floor window open slightly).

plaster sucks up water/moisture like there's no tomorrow. your man is correct about the salts and the rendering will fix it. the reason for rendering is to stop the action of any remaining salts.

any remaining plaster below ~ 1m and above the new render needs hacking off and then rendering. this will sort it as long as the chemical dpc is good (which sounds to be the case given there is no damp on the plaster over the new render).

knocking the plaster off is easy (even easier if you have an SDS hammer drill & chisel attachment - don't think on the small areas / 1 off job you would need one though, just a lump hammer and 4" chisel and take you time).

putting the render back on and re plastering is not an easy job and you may be better getting your man or someone else to do it. if you can use a trowel (8x4 flat plate type) and don't mind using a mixer then you should be able to do the rendering (you will need instructions) and then get plaster in to put the skim finish on.

i think the original surveyor would have spotted if penetrating damp was the cause (it's usually fairly obvious). i don't think the problem is penetrating damp though. the knock off and re render should have been to 1m in the 1st place. we can go through the steps to rule out penetrating damp though if you need.

 

[anobium]

You say porch/hallway, are you saying that there is a door subdividing these two.
If so get somebody to check the porch floor as there is every possibility that this is solid.
If it is let me know and then I will advise you further.

Sorry this was meant to be a response to another topic on damp

 

[Support Site Cardiff]

i work for a specialist waterproofing supplier and we have branches all over britain. there is a product called Thoroseal or another called Vandex which are cement based slurrys and have been used on a number of walls with damp problems. my name is Richard and you can ring me on 029 2046 5553 and i can give you our nearest branches number.