How to Build an Angled Roof (with Tiles)

Step by step how my roof was made
Roofing is the trickiest and most important part of a house build. As I’m sure you know, the roof of my old barn is on! It’s covered in beautiful traditional Spanish curved tiles too (collected from anyone I could lay my grubby, pertinacious hands on). But I’m not going to lie; I’m not a fan of tiles. Living roofs will always be my favourite. There are so many advantages to them, and they are a heck of a lot easier to construct.
 
Even so, in many places in the world, the tiled roof is the norm. So here’s exactly how we (ahem, Brian) made mine.

Levelling the walls.

​1. Raising the roof and squaring the trapezium
I wanted to slightly increase the height and pitch of my roof without impacting the character of my old barn. So first the walls were built up and levelled using clay bricks mortared with limecrete. As every single wall is wonky (the barn is basically a trapezium), this was trickier than it appeared. The roof (which is rectangular) needed to squat on the barn at a slight angle. This is of course a neurotic’s nightmare. So if you like everything minutely straight, all I can say is don’t buy an old building. Me? I like the incongruity, and it’s perfectly in keeping with the nobbled, nothing-is-straight personality of my old Asturian barn.

2. Adding the wall plates (15cm x 15cm)
Next, two 15cm x 15cm wall plates (horizontal wooden beams that rest on the walls) were mortared onto the bricks with NHL (hydraulic) lime. Why hydraulic? I wouldn’t recommend lime putty here, even with a pozzolan, a) because it takes too long to cure fully and you need that roof structurally sound fast, b) NHL lime is more cementitious than soft lime putty, and in heavy structural jobs like holding a roof on, that’s what you need.

Important note: You can't just mortar the wall plates on and hope for the best. They need to be tied down to the wall. I mention this at the bottom of the post, but it's since become clear people don't read that far:)) I'm still tying the thing down, but once it's done, I'll share that bit too.

Wall plates (15cm x 15cm).

3. The ridge beam (15cm x 30cm)
Once the walls had been levelled and the wall plates were attached, things turned rather exciting on Mud Pico. We needed to lift the massive central ridge beam up and across the middle of the barn. It was a momentous day sloshing with adrenalin, and frankly by noon I thought someone would die (or at the very least suffer a hernia).
 
We couldn’t use a full 8-metre beam because we had no cranes nor machine lifting tools, just human muscle. For those in the rich West, who to my Turkish way of thinking seem to be extremely dependent on machines to do everything, just note: where there’s a will, there’s a way.

The ridge beam (15cm x 30cm).

So in fact there are two 4-metre-long 15 x 30s joined together to create the 8-metre ridge beam. The beam is supported in the middle by a vertical central pillar (two fat pieces of ancient chestnut), which all rests on a horizontal 200-year-old massive chestnut beam that runs through the middle of the barn.
 
Important note: The two ridge beams aren’t just screwed together using brackets! Notice they are bolted top to bottom onto that horizontal angled wooden brace, which then rests on the vertical central chestnut pillars.

The two joined ridge beams rest on a central pillar. The red arrow points to the brace. The green lines show where bolts are.

4. The rafters (7cm X 15 cm)
My roof comprises 32 rafters (16 on each side), and all have been bird-mouthed to fit onto the wall plate and the ridge beam. Each of those bird-mouths was hand-sawed by Brian. For those doing the math, yes that’s 64 bird mouths in 7 x 15 rafters. And yes, that is indeed hard work:) It seemed like the poor guy was sawing for about a week. Brian, however, was stoic in the face of this brutality, merely murmuring between the clouds of sawdust things like, “who needs a gym?”

The rafters (7cm x 15cm) bird-mouthed.

5. The spacing
My rafters are fairly heavy-duty (7cm x 15cm), so for my tiled roof, a 50cm span between each rafter was ample.

Spacing rafters (50cm span in this case).

6. Roofing Boards
Now, if you have plenty of money and time, you would lay some lovely wooden roofing boards at this point, then add your insulation on top of that, then roofing felt, and finally tiles.
 
Me? I was out of money and very very pushed for time. So we screwed a kind of chipboard (sawdust heated with resin and turned into planks) straight down onto the rafters. I will add insulation and some pretty cladding on the inside later when I’ve saved a bit of money.

Roofing boards.

​7. Waterproofing
This for me was the most annoying part of this roof. If you are building a modern house with normal roof tiles, then all you need to do is use a lovely permeable roofing membrane, and you’re away. I’m not building a modern house. Basically I live in a museum, so I am bound by law to use tejas curvas, which sounds like something the inquisition threatened witches with, and in retrospect probably is.

Tejas curvas (curvy tiles) are of course much more beautiful than their less exacting modern counterparts. In truth, I would probably have used them anyway out of respect for tradition. Personally I think tacky soulless ugliness is as visually polluting as bitumen membranes. But...lovely as these tiles look, I cannot deny they involve a colossal waste of resources.
 
Tejas curvas cannot be nailed into place. In bygone years, when wood was aplenty, the locals would use chestnut beams separated at a fairly staggering 15cm, and rest the tiles in the gaps. Today of course, this is an unthinkable waste of trees. Also, in those days, every time a tile cracked you had to replace it fast as your roof would start leaking. So for these tiles some kind of waterproof membrane is necessary.
 
Today, especially for tejas curvas, a type of bitumen membrane has been produced, complete with ripples that you rest the tiles in. You might argue that bitumen in and of itself isn’t so bad compared to plastic (I mean at least it breaks down – plants can grow through bitumen in a few years), but I daresay other crap is impregnated in the bitumen to mould it into a harder rippled shape.
 
Is there another way?
If you have time and money, you could I suppose lay a nice permeable roofing membrane down (though hey, I’m pretty sure these involve micro-plastics somewhere too), and then create the ridges for the tiles out of wood (which, unless you are recycling, has of course been cut from somewhere). Whether you deem this method more or less ecological is a matter of opinion.

Bitumen ripples.

8. The tiles (tejas curvas)
I’m sorry to say the tile drama doesn’t end with the bitumen boards though. Once those are down, you’ve now got the unenviable job of fixing those wretched tejas so that they don’t blow away in the fairly gusty Atlantic winds that charge around up here. Traditionally, folk covered their roofs in rocks. I must say, I quite like the rocks myself.

The roof in the beginning, tied to a tree, with tiles held down by rocks.

​On my other two small cabañas, I used limecrete to stick the tiles together. This mostly worked, except on one edge, where ultimately I had to add the rocks again because they were ripped off in a gale. The trouble was, limecreting the tiles together was utterly exhausting, material-heavy work, and I hated every minute of it. This was actually the original reason I decided to get someone else to do my barn roof. Limecreting those tiles really broke me (carrying heavy buckets of crete on the roof, plus a water bucket, and trying to fix the tiles without dislodging the ones you’ve just mortared all on a pitch far too high...nah. Not doing it again.
 
So when Brian took up my roofing gauntlet, I simply did not feel I could ask him to do what I wasn’t prepared to do myself. He wanted to use tile glue, and frankly I just let him. It isn’t eco. It isn’t nice to use either, in my opinion. But on the plus side you don’t need much of it.
 
In hindsight, what do I recommend for tiles?
If you use all brand-new tejas curvas, then there is a better option. You can fix them with special clips, and use minimal limecrete or glue. I especially wanted to retain the old look of the barn though, so my second hand tiles were far too warped to use clips with. I think a lot about what I would have chosen to do had it been me wrestling with those tiles. Honestly I’m not sure. But maybe, just maybe, I’d simply have slung them down and ballasted them with rocks, like the old days. That would of course mean I’d be up there again in a couple of years repairing and replacing, but the tiles would at least be easier to lay in the first place. Hmph. Tejas curvas, it’s a tough one. If anyone has come up with anything easier and more sustainable, let me know.

We foraged second-hand tiles from all and sundry to put on my roof.

Still to do:
I’m very grateful to Brian for the incredible effort he put in to making me a solid and beautiful roof. I also learned a stack of things from him in the process. Brian and Julia’s shift is over now though, so the rest is up to me:) One crucial structural job that people all-too-often forget in the heat of the roofing adventure, is tying the thing down. I know more than one person who has seen their roof fly, or lift alarmingly. It might seem impossible with the weight of it, but if a heavy gust can get under an eave, it can start to lever it off the wall. In my earthbag house in Turkey, we tied the roof down with ropes cinched through the earthbags. Stone houses are different though.
 
Roof and wall ties
I have a number of techniques I’m using to tie my roof down, and will write a separate post on it next month once it's done and I have photos to illustrate it.

And it's done!

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