Basic cellar lining for workshop

[Andy Mac]

I have a 12 x 12 cellar which isn't wet and has never flooded in the 9 years we've lived here, but as all old cellars are a bit moist, I'd like to line it and add ventilation before I move a metalworking workshop in, consisting of a lathe, a mill, bandsaw, media blasting tank and many hand and power tools, all no doubt prone to rust in damp air! The cellar stays between aroun 15 - 18 C regardless of the ambient temperature, so it is much prefereable to my current workshop (garage) which varies between about 5 degrees lower than ambient in the winter, and 300 degrees higher than ambient when the sun's on it!

 

The cellar is typical of a mid 1800's type. Double brick walls, no cavity, with around the upper 2ft of wall being above ground (the house is built on a slope at the foot of the Malvern hills). The existing floor is red brick, laid on their side so taking around 4" of height. There is an old wooden exterior door and a small cast iron window at head height. I plan to replace both of these during the update, perhaps with a small extractor fan in the window / vents in the door to allow airflow. As the house is on a gentle hillside, there is already a drain in the corner of the cellar which exhausts into the main drain going down hill from the property, even though as I say there is never any sign of puddles.

 

The route I am leaning to following is a membrane liner (the dimpled type which allows air movement) and a concrete screed floor.

 

I plan to take up the loose brick floor before screed / membrane, but obviously the membrane needs to sit on a hard surface. So my first question to the experienced folk here is -

 

Do I put down a thin screed (say an inch?) in order to give the membrane a hard surface to sit on, and then another screed on top of the membrane? Currently, the drain is below the level of the brick floor so I can leave the edge of the membrane open around that point for airflow. 

 

As this will be a workshop rather than for habitation, I'm assuming that regs are not required?

[tonyshouse]

My advice for what it is worth would be no membrane, in the occupied basement the partial vapour pressure of the moisture in the air will be higher than the partial vapour pressure in the air pockets in the wall or in the ground beyond the walls. THEREFORE moisture in the air will move outwards and downwards from the room into the ground.

 

with membranes there will be a danger and at times of reality that condensation will occur and sweating, silverfish, mould and other problems to start happening. Most likely high up on the coldest parts of the walls in very cold weather 

 

Small quantities of liquid water from inside or outside will not be stopped by the above process but will be dealt with slowly and effectively. Plumbing leaks and flooding won’t. 

[Andy Mac]

Hi Tony, and thanks for the reply.

 

Two of the walls are 'dry', as in they face other parts of the house (a partial depth inaccessible cellar under the lounge and kitchen) and only two walls face the outside world to about 3/4 depth. 

 

I was thinking about dropping rad feeds down to a small 'background heat' rad - so would this improve things by the same way of it being occupied (probably only 3 hrs a day in the evening)

 

What would your suggestion be re. wall finish if I don't use membrane then? A breathable render or suchlike? I'm obviously no expert.

[Andy Mac]

Been reading up a bit more on this, and it seems you may have allowed me to dodge a bullet.

 

So some sort of lime mortar for a wall finish, but what about the floor? I have a heavy lathe and milling machine and wanted a solid, level pad for them to sit on and the existing bricks may not cut it. Do you have a suggestion for the floor, given that I now understand that cement / concrete may just succeed in keeping moisture *in*

[markc]

You really need a concrete floor to bolt a lathe down … unless it’s a very big old one.

milling machine will sit fairly well on any floor.

might as well dig out, insulate and pour a decent slab … old damp cellar floors are murder on your feet.

[Andy Mac]

I have a big piece of 1" thick polyurethane foam I stand on. The concrete garage floor is FAR colder than the cellar! ?

 

So, I take it it's OK to have a concrete slab floor as long as I allow the walls to breathe then?