How much for new Damp Proof Course.

Johnjohn

Can I ask what you are experiencing that makes you think that you have rising damp?

Flaking paint on inside of bay window with salts behind the flaking paint. The house is Victorian and doesn't have a DPC. There is concrete outside the bay window so there is the possibility of the problem being caused by rain splash. The plaster (sand-lime I think) seems basically sound although a bit damp.

I will probably inject Dryzone at close to ground level as there doesn't seem much point in injecting at 150mm as most of the damp signs are below 150mm anyway so it would be pretty pointless. I will then apply colourless water repellent to the outside wall of the bay window (bricks). I will then see if the problem gets better over the next 12 months before deciding whether to bother replastering.

Before you ask, the problem isn't condensation. It is impossible in my house due to a wife who insists on keeping the heating on full all day whilst keeping windows open for ventilation. The cost of injecting some Dryzone and painting on some water repellent will pale into insignificance compared with my gas bill.

25rts

Hi Johnjohn

I have been in the industry since 1986 and have surveyed thousands of properties the majority of which have been Victorian and the majority of those which were found to have slate DPCs although some of these DPC's were found some way below floor level (600mm on one occasion).

I am not anti chemical DPC and have both installed and recommended installation numerous times but I do often see misdiagonosis of rising damp for what I sometimes consider very obvious defects although not necessarily to the general public. Hygroscopic salts are rarely visible so I would be surprised if that is what you are seeing. Is there a drip throat (groove beneath the concrete sub sill) or does the damp continue along the length of the wall?

oneeye1

jimbo10 wrote: »

Does the new plaster that is used have to be a specific type or can you use ordinary gypsum plaster?

no it cannot be a gypsum based backing plaster the prefered method is sand and cement with additives.a gypsum finish can be applied to this

de1amo

i am reading with interest with a vague connection to this--i saw a house last summer in a holiday resort near the city i live in in Turkey--here once people see the marks of dampness they all reject places out of hand and the price becomes 'never too low'. it was a 3 storey place and showed dampness on all 3 floors to eye level-the roof was good -however due to it being a holiday home it had obviously gone for long periods without being used--i wonder if this was the real cause rather than 'rising' damp??? from what i have read here it seems the logical cause

Johnjohn

Is there a drip throat (groove beneath the concrete sub sill)

No there isn't and I expect that is part of the cause of the damp, although when it is raining it looks like rain splashing from the concrete is probably the main problem. The house definitely doesn't have a DPC, though. However the only damp that is significant enough to bother me is in the bay window.

stevencalvert

The slate does not deteriorate however as the house moves the slate cracks and allows water penetration by simple capilliary action all of you arm chair experts should learn lesson 1 before making a comment on things you don't understand rising damp is a major problem in london and the south east as there are thousands of underground streams that where just built over dig anywhere in the south east and after about 1meter you will find water so a concrete floor without an effective D.P.M or a brick wall without an effective D.P.C will allow water penetration and that needs to be stopped at floor level

salar01

Hi Have previously posted but think I gave incorrect information. My house is early 1900's. The livingroom floor is concrete with red flooring asphalt on top. I don't have damp proof course. My fireplace is open with flue and working. I have problems with damp in the alcoves (on either side of the chimney breast) and the chimney breast. Tried an anti damp paint under my emulsion but now have a dark mark and what look likes water half way up the chimney breast (either side of the fireplace). In both alcoves I have what looks like someone has just stuck grit on the walls. I have borrowed a dehumidifer which has been on for three days now and doesn't seem to have made any difference to the dark marks/water. Any suggestions a) What is the problem in both areas? b) What would be the solution?

Would appreciate any help

David_Aldred

Hi,
Chimney breasts can be problematic especially when no longer used for their original purpose of having a roaring coal fire constantly within them. Often the hearth has no barrier to ground moisture beneath it with a relaince upon the heat from coal / wood fire in constant use keeping it dry. When no longer used dampness can strike up from the hearth into the surrounding area including the infill material behind the fire-back forming a moisture resevoir.

The products of combustion (i.e. the soot) tend to migrate into the surrounding area especially if the area becomes damp due to say reasons as described above and can cause havoc by way of disrupting plaster and causing unwanted dampness.

Party wall chimney breasts where there is a chimney breast back to back often compound the problem especially when the chimney breasts may be offset to each other.

Open chimney pots allow rainwater to come down the flues but tends to be seen as a problem to upper rooms before first before it migrates to lower room areas but this is not always the case.

Condensation within flues can be severe and add to the problem.

Gaps at solid floor / wall joints (even as little as to allow a knife blade to be inserted) can allow dampness to emerge there due often to the floor moving seperate to the floor.

If you are correct and there is no damp proof course then the wall may be subject to rising dampness.

If the floor level on the other side of the wall / chimney breast is at different level (i.e. higher) then lateral penetrating dampness can effect the wall / chimney breast.

If the alcoves are cavity wall construction debris within wall cavities could bridge any damp proof course if present (which you say is not in this case).

Once plaster is contaminated it will not recover. Substrate preperation (including new dpc if none present), sealing any open floor / wall joints and re-plastering or dry lining to an appropriate specification is often necessary. If hearths lack a barrier to ground moisture then replacement with one that incorporates such is worth consideration. Works to party walls (such as new damp proof course or waterproof grade re-plastering) including the chimney breasts may be subject to the Party Wall Act.

Hope the above is of some use to you, kindest regards David Aldred Independent damp and timber surveyor.

salar01

HI David Thank you so much for your help. I have borrowed a de-humidifier to see if that helps it's now been on for about 5 days but doesn't seem to be improving anything. I am going to sell my house within the next few months so really don't want to start doing the amount of work it sounds like it needs. I'm happy to reduce the price of my house to cover DPC but the wet marks on the chimney breasts stand out like a sore thumb and is sure to put people off

doit

Interesting. I am in the process of buying a two-bedroom house built on chalk rock and surveyor report points to serious rising damp due to age of property (around 1900) and because last reburbishment was about 30 to 40 years ago. I read that the metres used by surveyors are build for timber and only read the surface. I am certainly going to be careful before doing a DPC, though I have to strip the walls down anyway. I read that one could take a sample drilled from the lower section of the wall and get it examined for their moisture and salt content to determine whether there is serious rising damp. Does anyone know a lab I could use to sent the samples?