Laying Terracotta Floor Tiles

[Zippy86]

Hi, I wonder if anyone can help please...

My partner and I have recently bought a beautiful Victorian cottage (1885) which we are currently majorly renovating; we wanted to keep as many of the original features as possible but sadly the building hasn't been looked after and a lot of its originality is having to be replaced

However, in the kitchen and dining room laid the original and intact terracotta tiles which we have taken up to relay to solve the damp coming through them..and this is where we're stuck; :roll:

1) We have been advised not to lay the floor with concrete OR a damp proof membrane as this can cause the damp to redirect up the walls, but to use Limecrete instead to allow the floor to breathe (we've learnt a lot about letting this cottage breathe)

2) We have looked into this and found equal arguments for and against each

3) It has been suggested that we create a re-enforced suspended floor to lay the tiles on top of to solve the issue


Has anyone come across this situation before and if so, how was it revolved? We really would love to keep the tiles!

Many thanks in advance x

 

[LadyArowana]

Just bumping this up for a new poster.

 

[Zebra]

It sounds like you are already in possession of many of the ideas surrounding damp in old houses, as you say you have learned a lot about breathability in the time since you purchased the house. If you have already lifted the terracotta tiles, then you have two separate issues - whether to reuse them or not, and whether to have a breathable or non-breathable floor.
As for dpcs pushing the damp into the walls, this may or may not occur, and it is very hard to say whether or not it will. Each case is, of course, different, and the porosity of your brickwork will have an impact upon the situation, as will whether there is any sort of damp proof course, slate perhaps, in your walls.
It is tempting to say that you ought to go either totally one way or totally the other - ie either full breathability in both floor and walls, or full dpc/dpm which overlap and can be guaranteed to keep out the damp.
Any half-measures (floor but not walls, or walls but not floor) may lead to an unsatisfactory outcome, solving the problem in one area but making it worse in the other, but this can't be predicted in every case.
How do you feel about waiting a while? You're down to soil now, presumably, in those rooms? Do you have any sort of damp-proof course in the walls? (I know some Victorian cottages had slate damp proof courses, I don't know whether yours would fall into this category). Is there damp in the walls now?
What was the situation before you took the tiles up? Were the floors sodden? Why? Was the house left empty for a long time before you bought it? It may be that giving the house an airing and some heating would have solved the breathability issues by itself...
It's difficult to give a definitive answer as to what would be best. Often it is the case that you try one thing, give the house time to dry out, see if it's worked, try something else... But you're best off looking for the causes of the damp, trying to eliminate them, and allowing the house time to dry before doing anything drastic....

 

[formerly known as]

I have to ask - why did you take the floor up?

 

[angrybird]

I don't have any DPC under any of my floors because I didn't want to loose the original quarry tile and flag stone floors and I love the way in which they are layed.I know they will never go back down the same again if I lift them.
The only time we get damp floors is when its very hot outside, so the past few weeks we have had very "sweaty" floors! I just turn on the dehumidifier and this dries the damp up.
In an ideal world it would be lovely to have underfloor heating but i'm not going to sacrifice my lovely floors for that!

 

[Flyfisher]

We have a room with, presumably, the original pamment floor laid directly on the ground. It looks and feels bone dry.

However, it used to be covered by a wooden floor, which had been laid directly onto the pamments supported only by thin 'joists' of around an inch or so that had been packed to level the floorboards (I.e., not a suspended floor with any ventilation). I don't know the age of the wooden floor but I do know that about 30 years ago it was pulled up because it was damp underneath and had largely rotted away.

Some years ago we stored some cardboard packing boxes in that room over winter and when we revisited them some months later the base of the cardboard boxes were damp and mouldy. Other items in the room that had air gaps between them and the floor were, and are, fine.

My conclusion is that the floor is breathable and is, indeed, breathing, which is not a problem as long as the 'breath' is allowed to dissipate through adequate ventilation . . . . which is where things often go awry in our modern quest to insulate and draft proof our houses. If we sleep with our bedroom window closed there is usually condensation on the glass on cool mornings whereas there is none if we sleep with the window open (as is usually the case).

So, a slightly 'damp, stone floor probably contributes no more moisture into a house than the people living in it by their breathing, washing, bathing, showering, tea-making, etc., and if all of that moisture is trapped then it will likely condense somewhere and give rise to the problem we call 'damp'.

Is it worth dragging out the old 'rubber glove' analogy? :wink:

 

[Keithj]

On the shelf beside me (upstairs) there is a panel with a load of met information on it. Among the information is humidity - 64% and 15.7°C outside, 43% and 26.0°C inside (directly above the computer, which has been working hard). Down in the kitchen a different gauge says 18°C and 70% RH. That has terracotta floor tiles laid on a sand bed laid on the earth. It's been that way for a very, very long time. 43%, 64% and even 70% are not "damp". It gets a lot higher after a thunderstorm. I've seen 98% (briefly).

I would argue that ventilation and breatheability are key.

 

[formerly known as]

My ground floors are a mixture of floor brick and pamments laid on sand on earth. When I first bought the house, the 1980's builder had laid a screed over plastic and covered this with a mixture of lino and rubber backed carpet - this combination had lead to high levels of damp. I removed all of this and the floor dried out almost completely within two days (this was during the summer). The only 'problem' I have now is when it gets to springtime and the air temperature starts to rise and the equilibrium between air temperature and the floor temperature needs to be met, until this is met, the floor 'blooms' slightly, but this is only for a few days. As already mention, traditional floors need to be able to breathe in the same way that walling does.

 

[MatthewC]

Zippy

There's a lot of good sense mentioned in the previous posts, so here's my tuppence worth.

I laid a limecrete floor in my kitchen where there were damp and very poor condition quarries laid on a weak thin mortar base. I could have then relaid more (better) quarries but I actually used imported limestone flags without sealing. I'm not sure why you say

2) We have looked into this and found equal arguments for and against each

as I find that kind of worrying! My limecrete floor has been excellent and other than the cost and hassle of installing, I really cannot see the downside so I would always recommend this solution.

3) It has been suggested that we create a re-enforced suspended floor to lay the tiles on top of to solve the issue

Don't do that either - you would either have to dig out a lot (so then you might as well lay a limecrete floor) or else you would surely raise the floor level by a large amount (which I doubt you could sensibly do).

However, no-one above (AFAICS) has mentioned external ground levels. With a porous wall, this aspect is critical. If at all possible you need to get the ground level down to at least 6" below the internal floor level. This of itself will help the present floor to dry out (give it time!), and if I had not done this then my nice new limecrete floor would still have been damp (and would remain so).

See my blog (click the blue spot on the right) and filter the tags for limecrete etc for the full story of my floor (or scroll back to about April 2011). Happy to advise further.

Matthew

 

[formerly known as]

in some cases, it may not be possible to drop external ground levels to 150mm below internal FFL, due to potential undermining of footing. I would suggest that as long as external surfaces are free draining, ground level can be equal to internal FFL. Where external ground has to be retained by the walling due to levels, this should be detailed accordingly. Remember that the 150mm advice is based on modern construction - ground level from DPC.

So, carrying on from M's advice, if there are external concrete paths etc, get rid of them and ensure that downpipes are carrying water away from the building to an adequate soakaway ..... old saltglaze is seldom complete.

 

[Keithj]

Indeed: external concrete paths up against the building are bad news.

Our house internal floors are a few inches below external ground level. There is a French drain, which takes the surface water away from the wall. I don't know whether or not it was essential, but our expert adviser was strongly in favour. It certainly did no harm, and we have no damp problem.

We used a French drain as part of the solution to a 50-year-old damp problem in the church. Again, the inside floor is lower than the outside ground level. The damp has almost dried out now, a year later. The walls are very thick and are still blooming a little, but the source of the wet has gone. The floor is brick/pamments laid with no spacing and no grout. It shows no sign of damp.

 

[MatthewC]

I would suggest that as long as external surfaces are free draining, ground level can be equal to internal FFL.

I would suggest that the above is a less than optimal solution which would still cause issues with dampness. Even ground that drains freely will affect the amount of water in the walls and hence the floor as well. Although I mentioned 6" of clearance (which happens to be the same as modern standards), I think the normal recommendation for old houses might actually be more.

Mind you, my kitchen (now with limecrete floor) had the external ground five inches ABOVE the floor level, so it was not surprising that the floor was damp. I also had concrete paving up to the wall at floor level beside the lounge, which had a suspended wooden floor - you can guess what happened to the joist beside the wall, and the ends of the floorboards.