Tejado is the Spanish word for roof. We have a very old classic tejado. It is constructed by putting wooden beams on top of the walls, and perpendicular to that thick reeds. On top of the reeds they apply a layer of sort of mortar. That sort of mortar is a soft mixture of clay and gypsum. On top of that are placed the classic arabic tiles.
This tejado probably is 100 years old, the beams have porcelain electric insulators in some places that were used up until 1925, nicely dating the roof before 1925. Basically the roof is fine, these tiles are very strong and thick terracotta. But, certainly the roof ridge needs maintenance. The rest of the roof has the tiles alternating up-down-up, and at an angle, so in principle that cannot leak. But the roof ridge is just horizontal tiles on top of some cement, with the end openings filled with mortar. And, most tiles there were loose, and/or with gaps, and many end bits missing or cracked. That should explain the leaks we have experienced last winter!
Our constructor has worked on the roof a few years ago, but did not have enough time for more work short term, and the rainy season is approaching.
Engineer Jansen does not really suffer from vertigo, but does not like the idea of moving around a tilted roof. Even if it is not a steep roof. Yet he got over his fear, tied the ladder tightly to the chimney, hauled up 4 foam mattresses to be able to crawl over the roof on his knees, and inspected the roof. He did not like what he saw.
And (sorry it's not sharp, the engineer was shaking):
There are 41 tiles in the roof ridge, about 35 were loose and could easily be removed, like this:
Note the marker lines that tell how they were positioned before removal. Also note that this bit is filled with some mortar, but the mortar did not touch the tile, so that was just held in place at the sides, and by sticking under the tile before, and overlapping the next tile.
Where the tiles overlap they should have some (lime) mortar, but they did not, any more.
In the picture above you can see that the ridge is filled. And the filling is.. dry soil and some stones. Engineer Jansen removed all that dirt using the ash vacuum cleaner that we normally use to clean the pellet stove.
As this was a job that could not be done in one day the tiles were put back, fixed with bags of gravel.
To fill the roof ridge Engineer Jansen went back to a classic building material: lime mortar. Why? Because lime mortar is soft and flexible, and old tiles need that. If you use a modern cement the joint will be very hard and inflexible. What happens when the construction ages and the mortar is at end of life (50 years) a modern cement cracks and breaks the brick or tile that it is fixed to. When a lime mortar joint breaks the lime mortar breaks, but leaves the tile or brick undamaged. Old bricks and tiles are not as hard as modern ones, though these roof tiles are STRONG!
Various restorations explained in youtube videos made use of a 3 : 1 : ca. 0.8 sand : lime : water (by volume) mix.
Lime is available here: Gecol Cal de Construccion
There are more lime mortar products, Gecol advised Gecol Sec cal-H, but not readily available.
The difference is that Cal de Construccion is just 95% lime, and you have to add aggregates like sand and bits of stone to make a mortar. The other products are readily mixed. If you are interested (yes you are) see Gecol Lime Mortars.
(I went to the local building materials supplier, to ask for an advice. The expert was called, who told me Gecol Cal was mainly portland cement. It isn't, it's 95% pure lime. So much for the experts. They don;'t know anything about lime mortars.)
Anyway. Besides lime mortar the engineer did use a modern product: PUR foam for tejas. Recognize the tiles on the label?
Planned to use just a blob at the ends of the tiles, but decided to use more, as it turned out to be very difficult to actually stick the tiles in place with just lime mortar. The how-to videos showed that they use a blob of lime mortar to fill, and on top of that a line of pur to glue the tile.
The pur also peeped through the joints at the side, which is not bad actually. When hard the surplus is easily removed.
To fill the joints, with the PUR scratched out, another product: Lanko 227 Imper Megaflex, a cement-ish product that contains fibers. It's usually used for repairs and to fill cracks. It adheres well to both cement and ceramics. So.
It's expensive too, a 15 kg bag is €75. For the roof ridge I have used 2 kg, but the rest of the roof will need more. You need to use an exact amount of water, and mix it with an electric drill mix thing to sort of a toothpaste consistency. Then you can fill your cracks, using a spatula or a brush. I used a paint brush mostly. One layer already looks fine, but the instructions tell you to apply two coats. Engineer Jansen obediently did so.
Well. We will see if this improves the roof. That really is necessary, last winter was cold and wet, and the roof was also cold and wet, and leaked. Not really a lot, but a drop of water every few minutes is quite irritating.
Secondly, the gypsum layer under the roof tiles gets damp, which makes it lose any insulating properties it might have had. And heat that touches a wet roof vanishes.
Thirdly, after filling the gaps we had a bat in the living room. In total silence it swooped around the room. Poor thing, it probably lived in the roof ridge, slipping in and out through the gaps, that are now filled, so the only exit was to the inside of the house. (Removed the mosquito screens to let it out.) As the bat could slip into the living room from the roof ridge, probably warm air could slip out, too.
We can properly heat the ground floor with the pellet stove, but could not maintain a comfortable temperature upstairs for longer periods. Which makes sense now, I think. We'll see how it is this winter!
(This was a whole week working HARD, up and down the ladder, about 100 kg mortar was processed, the engineer is not that young any more, obviously.)
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