Stopping water ingress into basement from external stairs

[natashap]

I own a Victorian era converted basement flat. The area directly underneath a set of stairs that lead up to the ground floor flat is becoming increasingly damp, mainly on the floor as the ceiling and walls have been tanked previously. I have had two companies assess the situation and both have said I should not be treating the damp, but treating the root cause, which is water ingress from the stairs above. My neighbour appears to have some sort of waterproof sealant (possibly mastic asphalt?) around the edges of their stairs and I was wondering if this could be a suitable solution for me? If so, what sort of companies could help me with this? If not, what do you think I should do instead?

Thank you

 

[Nemesis]

While it sounds as though both companies gave sound advice about treating the cause, did they not also make any suggestions about what to do?

Can you post a picture of the problem?

 

[chuckey]

I can't figure out why someone would tank a ceiling, if the water level was that high the flat would be full of water?
There are two area flat setups that I know, firstly, the double fronted house with impressive stairs in the centre of the building. On the sub-ground floor, the area under the stairs, which is outside of the main footprint of the house, is available for accomadation (my mate used it as a wine cellar). Is this your layout? If it is your "ceiling" is actually the masonary making up the stairs. The other sort is normally of the halls adjoining sort of terrace. The construction I guess is as above, but with a dividing wall down the centre of the stairs (above and below). The area's front door is normally set into the side of the walls holding up ther stairs.
The original damp proofing would have been welsh slates mortared to all vertical surfaces under ground. This would include the brickwork, right down to the foundations of the stair case. By now most of these vertical dampcourses have failed, the cure is to dig down to the foundations and cover the slates with some waterproof membrane and to include gravel/drains in the backfill, so as to lower the water table. Most "cures" involve tanking the inside of the building, but there are hidden downfalls, such as NO fixings to pierce the plasterwork (<1/2" long), difficulty of sealing pipes and other wires properly that pierce the wall internaly.
Frank

 

[Lime]

Close examination of the steps and the area around them may give some indication of where the water is entering.
Best done in the rain.
Filling gaps and cracks with a mastic or other sealant can only give a temporary reprieve but will be better than nothing.
Tanking the top and sides under the stairs was bound to be a temporary measure as the water accumulated behind the tanking and had no where else to go except down.
The tanking prevents any drying out too.
Do you own the steps?
If you don't you may find the occupier doesn't want mastic or seal placed all over their steps.

 

[Nemesis]

I do wonder too about the water held behind tanking. It has to get out somewhere and at some time. It may be that the water ingress is at the sides of the steps, in which case some lime mortar may help, but without some pics and a better description it's hard to tell.

 

[natashap]

Thanks for your responses. Unfortunately I do not have a picture. I also do not own the steps above but have written to the owner (also the flat freeholder) and advised them of the situation and that I will be getting some quotes before discussing the situation with them. I think they should be amenable to the stairs being asphalted.

Both companies that I contacted said I should get the stairs above asphalted to prevent further water ingress. One of the companies also said they would do further damp proofing of my flat too.

So essentially I am looking for companies that may provide me with a 'stair sealing' service in the West London region?