Cellar tanking

[sw2newbie]

Hi there,

I have a cellar in my Victorian mid-terrace property that has a height of about 5'10. I have had quotes to lower the floor, underpin the foundations and put in a light well so that it can be turned into a habitable space, but this will be prohibitively expensive. I therefore simply want to waterproof and finish the space so that it can be used for storage without everything becoming damp/mouldy/rusty.

I have looked into the various systems available and think that something like Newton/Oldroyd will be suitable. First off, does anyone have any comments on which of these two is generally better?

Second, is it always necessary to install a preformed drainage gulley and have a sump/pump included in the setup? There has never been any visible free-flowing water on the walls and there is already a drain in the centre of the floor that, having tested it, drains perfectly adequately as the floor slopes into the centre. Would it be sufficient simply to join the wall and floor membranes in the appropriate manner, which would allow any moisture to trickle down the walls and across under the floor to the drain in the centre? I could then install a flat floating floor on top of the membrane and perhaps install a sealed maintenance hatch in case access to the drain was required.

Third, none of the guidance available seems to say what to do with regard to a join with the ceiling. It might be a silly question, but is it sufficient simply to install a plasterboard ceiling under the joists of the ground floor, in the normal manner, with the wall membranes going up as far as the joists, or does there have to be some sort of joining of the wall membranes at the top? Would this cause any problems with moisture rising to the ground floor?

Thanks in advance for any help that people can give.

 

[DAZB]

Newton and Oldroyd are virtually the same in terms of installation and performance so no real advantage of one method over the other in my view. Regarding the drain , you seem to have it correct especially with providing an access trap for maintenance but I would also check out the type of drain it is and where it runs to by using a test dye or colouring because it will help in future if you know more about it. Lastly there is no special requirement for the joint between walls and ceilings from a membrane point of view so other than self adhesive scrim tape on the joint prior to plastering I would take the oppportunity to get plenty of insulation into the joist spacings and then plasterboard and skim the ceiling and walls.
One other point worth doing is to fit more airbricks if you don't have many as these will greatly help the ventilation of the walls behind the membranes.

 

[sw2newbie]

That's really helpful, thanks. As far as insulation and ventilation are concerned, is it necessary to insulate the walls between the membrane and the plasterboard as well as the ceiling void, or will this simply encourage condensation and reduce ventilation? Also, should the airbricks be ducted to ventilate the room itself (through the ceiling, probably), or the space between the plasterboard and membrane, or the existing wall behind the membrane? I don't see how it would be possible only to ventilate the existing wall as it will be directly covered by the membrane.

Thanks again.

 

[DAZB]

If you are using the room just for storage then insulation may not be important but I think it would be a wasted opportunity not to do as much as you can while you can and access is good. What I have done dozens of times is actually build a room within the room by erecting stud walls just in front of the membraned walls after laying the chipboard floor. Obvious care needs to be taken when fixing the sole plate so ensure fixings do not penetrate any floor membranes you use. You can then insulate the studwalls with kingspan or cavity batts etc.. before plasterboarding. The room within the room is ideal because it creates a gap between the external walls and this helps airflow while avoiding contact. The membrane has a profile which allows free flow of air to circulate behind it and you can provide a duct from any airbricks to direct the air behind the studwalls which will ventilate and help evaporate any moisture.