Relaying a Quarry Tile Floor

[simonanna]

Hi all,

We have just discovered this incredibly useful forum and have been reading many of the messages on damp and the lime/cement debate.

Apologies if this question has been asked already but we wanted to check the best solution for laying a quarry tile floor.

We have a 1920s red brick Victorian style mid terrace and have recently knocked through to the coal shed to extend the kitchen. We also dug up a damp concrete floor that was down in the kitchen. Now we want to lay a quarry tile floor on the whole area. The walls in the kitchen have at some time been cement rendered so we would also like to know whether we need to remove this and lime render instead.

We have been advised that we should lay a DPM and concrete floor and then lay the quarry tiles on a bed of mortar. Is this the best advice?

Thanks,

Simon and Anna

 

[inwood]

As you mention in your post the concrete floor was damp. Laying a DPM and then another concrete floor will force the water elsewhere - normally to the perimeter of the room and then up the walls. It may be that you have a DPM in the walls in which case this would be as far as the damp would penetrate. If this DPM is intact then the standard building practice would be to lay a DPM for the floor and dress into the wall DPM before laying the concrete floor ontop.

However if you have no DPM in the wall the new concrete floor will create further damp issues over the longterm.

An alternative (more expensive but in my view better in the long run) would be to lay a Limecrete floor. See http://www.limecrete.org.uk/ for details of Ty-Mawr's limecrete floor. There is no DPM used in this floor. The insulation material installed below the limecrete acts as a capilliary break, ensuring that no damp is drawn upwards. Any damp absorbed from the walls is released by the lime naturally rather than trapped as would be in a concrete floor.

I've used this very successfully in my kitchen and pantry (where the internal floor level is four foot below exterior floor level). I've also just relaid the quarry tiles on a lime screed and (when I finally get round to it!!) will be using a lime mortar to grout the tiles.

Hope this helps, if not post more questions there's plenty of people with lots of experience here willing to help out.

 

[Moo]

And do, please, remove that cement render.

If you're intending to instal fitted kitchen units, why bother to replaster the walls behind them? Nobody will be able to see them, so the bare brick walls can dry out in private.

 

[inwood]

I would look behind the cement render first - try chipping a bit off. If the bricks behind it are damp then yes it would make sense to remove and re-render in lime.

However since your house is relatively recent there's every possibility that the cement render is not causing any problems in which case I'd be inclined to leave it. Removing a stable cement render would cause more damage to the bricks than leaving in place. If it's above the DPM in the wall (if it exists) then there's unlikely to be any damp behind it unless damp is penetrating the wall from the outside.

 

[simonanna]

Wow, thanks for the quick replies inwood and Moo. We have just popped back to the house and think that we have found a slate damp proof course in the wall about two or three bricks up from the outside ground level. This seems to run right around the perimeter of the two outside walls breaking for the two doorways. There are two internal walls which are rendered, do we need to check for DPC there?

Limecrete sounds very interesting, are you suggesting that can be laid whether or not there is a DPC in the walls? Also if we were to go the concrete floor route how would we attach the DPM to the slate DPC?

Also thanks for the advice about the render, we tried to chip some off earlier and found it was hard as nails! Should we chip it off below the slate DPC and rerender in lime plaster or is this only necessary if not going the DPM and concrete floor route?

Thanks again!

Simon and Anna

 

[inwood]

The internal walls should also have a slate DPC. If the render breaches the DPC i.e. is applied below it, then yes it would need to be removed to above the DPC.

With regards the limecrete, yes limecrete floors can be laid whatever the structure of the walls (mine are stone rubble). I would give Ty-Mawr a call if you're thinking about the limecrete. They can give you more details specific to your needs. They can be contacted on 01874 658000.

If you were to go the concrete floor route you would need to remove about 20mm depth of mortar from the slate DPC (mortar will either be above or below DPC but between the slate and the bricks). The damp proof membrane can then be folded into the opened mortar joint and then re-mortared to hold it in place. However bear in mind that slate DPC's are not as effective as modern DPC's so laying a concrete floor may make damp issues worse.

Normally the internal floor level is at the same level as the DPC so there should be no need to re-render assuming your floor level is at the DPC. However if this is lower and the render has breached the DPC then yes chip it back to above the DPC.

In my house the render and plaster had been applied to floor level, wicking moisture upwards. I've chopped out a layer about 20mm up from the floor all the way around the room. This stops any moisture being drawn into the plaster and is covered by the skirting anyway.

 

[simonanna]

Thanks again for the advice inwood. I called Ty-Mawr who were quite helpful but want to charge £30 for a quote! This is refundable if you go ahead but if the lime route is going to cost a small fortune then that is £30 wasted. Could anyone let me know roughly how much their materials were so I can gestimate how much my 3 m by 5 m and 150 mm deep floor will be? Alternatively can anyone recommend other suppliers?

Thanks,

Simon

 

[MdB]

When I looked, an insulated limecrete floor was roughly twice the cost and about 30% thicker than the equivalent concrete floor. This is from memory but should give you a guide.