plastering a cellar/basement

[johnhiggins]

i am thinking of refurbishing my basement/cellar area.
it is approx 6m*6m square.

do i have to waterproof sand cement plaster the walls or can it be battened insulated and boarded out?

will the floor accept self leveller or will this have to be waterproof screed?

there is a window so ventilation shouldnt be a problem.

cheers for any help

john

 

[Tom.]

Do not attempt to 'waterproof' the cellar. If you have a damp problem on the brick surface, you can build a floating floor, and stud walls with ventilation all the way around. Cellars must be allowed to ventilate.

If you attempt to plaster it with sand/cement you'll end up with some serious damp problems.

You can render the walls with a sharp sand:hydrated lime mix of about 3:1. Cement does not allow walls to breathe.


Remember - no ventilation = damp = £££££

 

[johnhiggins]

thanks tom

would you recommend battening the walls out with timber and plating it or the render method

john

 

[shaggy]

Tom:

You can render the walls with a sharp sand:hydrated lime mix of about 3:1. Cement does not allow walls to breathe.

Can you explain that Tom? When you say cement doesn't allow the wall to breathe, which way do you expect the moisture to go - in or out?

 

[Tom.]

Tom:

You can render the walls with a sharp sand:hydrated lime mix of about 3:1. Cement does not allow walls to breathe.

Can you explain that Tom? When you say cement doesn't allow the wall to breathe, which way do you expect the moisture to go - in or out?

I would expect the moisture to travel into the building, and evaporate and exit the window. This is why its important not to coat the walls with anything - I mention using lime render over cement render (if you can't build false walls) because lime is better able to allow the ingress of moisture, and will thus lead to fewer problems with damp.

 

[Tom.]

thanks tom

would you recommend battening the walls out with timber and plating it or the render method

john

Batten the walls is the better option, although you'll have less space, you're giving the walls enough circulation of air to stop any damp. Make sure you put a vent on each wall to encourage circulation. Don't use any insulation. It may even be beneficial to install an extractor fan.

If you need expert help on this, goto http://www.periodproperty.co.uk/cgi-bin/discussing/forum2.pl there are lots of contributors who have indepth knowledge of dealing with problems such as this.

 

[shaggy]

Tom:

lime is better able to allow the ingress of moisture,

So you want the moisture to come in then? Isn't the idea to keep it out though?

 

[Tom.]

How would you stop it coming in? If you cement rendered the walls, the moisture would just build up in the wall and behind the render.

Unless you wanted to completely demolish the cellar, and place waterproof coverings inbetween the groundsoil and bricks?

In old buildings, you can't eliminate damp, you have to manage it. So long as the cellar has adequate ventilation, there won't be any problems.

 

[shaggy]

If the moisture would build up in the wall behind the cement render then it isn't coming into the cellar? Isn't that a good thing though, reducing the amount of moisture coming in rather than encouraging it?

 

[johnhiggins]

oops what have i started.

still confused

 

[Thermo]

i think the point tom is making is that the hydrostatic pressure will eventually blow the render. there will still be a fair amount of moisture coming in unless its fully tanked, so aqnything less than that will be a false economy

 

[shaggy]

The reason I'm interested in cellars is that I grew up in an Edwardian house that had one. My father used it as a workshop and did render the walls himself. He wasn't a builder but did a lot of diy and I helped him mix the sand/cement. The render was still on the walls when the house was sold about 20 years later.
There appears to be an obsession with using lime plaster on this site. I've hacked off tons of the stuff during my renovation years and had to barrow it into skips. I've always plastered walls with a sand/cement render and skim coat.
Tom is not concerned with the render blowing, he's saying that sand/cement will make the cellar more damp. I don't understand that.

 

[legs-akimbo]

You are absolutely right shaggy there is an obsession on here with lime plaster and most of those who praise and encourage its use dont know a fiddlers fart about it. Tom included.
There would be absolutey no merits whatsoever in using lime mortars in a cellar, and if you think so Tom then just what type of lime Hydraulic,lime putties, pozzolanically enhanced, hydrated???????
I have seen many simple requests here answered with the advice to use lime plasters on even a block built shed, (which led to disastarous results)
which is absolute nonsense.
In answer to the original request for advice, for a completely watertight application then there are very good and often expensive products (Sika) that work in conjunction with renders to tank a basement, or a process of tanking using simply sand and cement and waterproofers in varying batched mixes that will work guaranteed. However and most importantly THE WORST THING OF ALL is to batten out a cellar using mechanical fixings into the walls as this creates a whole series of weak points where damp WILL penetrate using theese fixings as the conductor.water is a thin man and will find its way through at the weakest points , if there are none then you will have a watertight conversion, ventillation is an issue that would need to be addressed on the jobs individual concerns, but is a minor issue on the whole.
If you know nothing of the fundementals of lime and have no experience in the use of and their varying attributes and also disadvantages then do not offer advice on their useage as this could and HAS led to some people with massive and expensive problems to remedy

 

[Tom.]

Seems like some of the people in here are more interested in time and money, rather than good sound practice (although legs-akimbo raises good points in general).

Cement mortar was used to point the brickwork on my house, long before I bought it. Many bricks have now had their polished faces cracked off during winter. Good idea then.

I've seen houses with non-original cement plinths that have terrible damp problems inside, and I've also seen what can happen when the wrong materials are used when restoring old houses.

The point is, the original builders knew pretty well how to build a house, and I don't for one moment believe there are any magical ways to eliminate problems the original builders managed quite effectively. Its just a license to print money.

Cellars are generally cold damp places. Sealing that damp out won't do you any favours, which is why I suggest using traditional materials only. Think of it this way - when you've had a shower, would you dry yourself with a polythene bag, or a towel?

/rant

 

[legs-akimbo]

I have argued at length in the past on here upon this very subject and in short will again make the point that lime mortars are used on permeable materials such as stone, brick and cob. The purpose being that the lime mortar will freely absorb and readily release moisture by evaporation. The use of modern portland cements on the other hand work simply because the materials of brick, block and stone are harder than the mortars theat are used in conjunction with them so do not need to freely absorb and release moisture as do the softer traditionally used building materials. In short modern materials compliment modern cement based mortars and there is no benefit whatsoever to be gained from lime mortars in theese circumstances.
As for lime mortars in a cellar that is plain daft!
The whole purpose of tanking a cellar is to render it watertight so to use a lime mortar would leave the wall surfaces permanantly damp as the ingress of moisture externally is incessant and leaves the internal surface obviously in a perpetualy damp state with no chance to dry.....bear in mind that the integral purpose of lime mortar is to release and absorb moisture, so in a basement it would be totally ineffective.
if moisture is stopped by a tanking membrane to the basement walls that is 100% efficient then why should condensation be any more of a problem in a cellar than anywhere else in a house. Effective tanking needs to be undertaken in the correct manner and is a time consuming and expensive process, at least in comparison to quick fix cures that have been suggested in this and other threads.