Damp Proofing Question

Very complicated damp basement - please help!

Hi! I really need some good advice.

I have a terraced Victorian house with a basement below ground & street level. There is a small area outside the basement door, 9" higher than the basement floor. This area leads to steps that take you up to the street. At the foot of the lowest step a drainage hole has been drilled for rainwater. The hole isn't lined, isn't a proper drain, and has no drain cover. (My surveyor said that over time, water draining through this hole could undermine the subsoil). The street is on a slope which is higher to the right and lower to the left.

On the right hand side, where the street is higher, there are steps down to a small cellar. The cellar is 90% dry, and there are occasional damp patches on the cellar floor. The previous owner had a line of vertical chemical injections just inside the cellar door, which start at the ground level of the basement and go up to the ceiling.

Just outside of the cellar door, in the basement, there is a high area of damp which is over 1 meter above the tide line. It then drops down with the wet patches mostly appearing up to 20cm from the level of the floor for the whole side of the room, with a tide line. My neighbour on this side has similar damp problems, but only where her property adjoins mine.

On the opposite left hand wall, where the street is lower, on the side near the outside steps and make-shift drain, there is a chimney breast quite near to the front of the property. The damp is quite high here, has penetrated through the chimney breast and continues across the length of the adjoining wall. It is not as bad as the right hand side and the neighbour on this side says she has no damp.

I have had two quotes which are very contrasting. One recommends dryzone injections, with no requirement to replaster, at £3700. The other recommends stripping the plaster off, making a french drain, inserting an air brick to the external wall, lime plastering the walls, tanking the walls only (but not the floor), and having a stud wall to allow for ventilation. This quote is for the same price.

I don't know enough about this to know what will work. I feel that the problem I have is a combination of rising, penetrating and condensation damp and want to find the cause so it can be properly remedied. I cannot inspect external walls for cracks in render because the walls that have damp patches on are party walls, attached to my neighbours properties, and I have tested my water meter to see if there is a leak to the water supply pipe. It seems to be operating correctly.

I think: raise the floor for sub-floor ventilation, lower the outdoor area, sort the drain, strip the internal plaster, inspect the brickwork and lime render it, then replaster. Am I way off the ball park here?

I would appreciate any advice and guide for cost.

Thank you!

Desperate female who has read way too many articles (named Emily)

3 Answers

Best Answer

without actually looking at the issue it is impossible to be 100 % sure of what is actually causing the issues,
more or less spot on,would re-plaster with lime plaster no need to render internally if lime plaster is applied properly, would also check the roof where the neighbours walls adjoins yours for damaged felt ,tiles, flashings.
as for the cost these materials are approx 5times the cost of their modern day equivalent, finding someone who can use them properly may be your hardest task , their is no cement or additives in lime plaster,render. anyone who tells you different run a mile from.

good luck Alex

Answered 6th Jul 2015

ADR Property Maintenance

Member since 1 Mar 2009

Hi emily, dryzone is an excellent product but only for rising damp above ground level, it is not designed for below ground, ring them and ask technical, it wont have any guarantee,

The lime plaster reacts with water and tries to dry out. However, the best methodology for below ground is a tanking membrane with a sump and pump but in my opinion 4 grand wouldnt be enough as i would start at 7k but would guarantee a damp free zone

Answered 6th Jul 2015

Signature Design, Build and Restoration Ltd

Member since 9 Apr 2015

Hi emily, dryzone is an excellent product but only for rising damp above ground level, it is not designed for below ground, ring them and ask technical, it wont have any guarantee,

The lime plaster reacts with water and tries to dry out. However, the best methodology for below ground is a tanking membrane with a sump and pump but in my opinion 4 grand wouldnt be enough as i would start at 7k but would guarantee a damp free zone

Answered 22nd Oct 2018

Costa Building Services

Member since 1 May 2017

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