Roof Making

First project, quite a low tech one... but hey...

Not that long ago, I purchased a building whose roof was made of cement sheets known to contain asbestos. As I intended to move in with my wife and kids, there was no way I was keeping it like that: So I decided to change the roof for a standard tiled roof.

An experienced mate of mine help me a lot and I thought I would pass on the info as it is really quite basic and really good fun.

First step is to get your figures right and order the materials. In our case, the roof is a very simple shape with just 2 planes. Each side will be about 4 meters in the slope and about 6 meters in length.

To decide on what section of wood you should use, you need to do some basic calculation:
You need to know:
How heavy are the tiles per square meter: Mine are 20 tiles/m2 and each weighs about 2.5 kilos so roughly 50 k/m2 (you can find this info in the tile manufacturer documentation(pdf))
How much snow/wind can you get in the winter: This depends on your altitude and location. I've got some tables that says for me, I need to add 70kg/m2, this is quite a lot but I live at 500m above see level and in a montaneous region.

With this, you should be able to calculate the weight per m2 that the roof will have to carry. I was quite conservative and went for twice the weight: It was my first roof and I'm putting my kids under it remember !!

You pay wood by the cubic meter, so, especially if you're doing a large roof, you don't necessarily want to oversize everything.
If you want to fine tune the cost, you can take into account the slope of the roof which alters the figures a bit, probably worth bothering if your roof is large and quite sloppy.

This photo is a before photo (it was shot in june, the finished one in february, hence the gloomy look... don't say it was better then please)

Once we had all the material, we started taking down the old roof. I wore a face mask to do so and made sure I wasn't breaking any of the sheet of cements to avoid releasing asbestos fibres in the process.

Asbestos is safe to touch, it's only if it reaches your lungs that there is an issue. This form of of asbestos isn't very friable so the risk is low. My local recycling center isn't equipped to manage those kind of waste, so I had to make special arrangements: These things obviously have to be managed carefully.

Each sheet weighs about 50 kilos and is covered in moss which makes it very slippery.

These need to be disposed of properly, as I found out not every ordinary tip will accept to take care of this waste which is consedered toxic. For my part, I had to call ahead and book a slot for delivery as the guys had to wear masks and wrap all the rubbish immediately. It's not that toxic, but you can never be too carfull.

Once the sheets are of, the wooden structure has to be ripped of: Some of the beams are damaged and the intended tiled roof will be a lot heavier: We need to have something stronger.

We'll only keep the largest horizontal beams, they're the only one that are sound enough and big enough to cope with the weight of the new tiles.

We start putting the vertical beams, The size you need to put depends on the weight you expect it to carry and the distance between the resting points. It's quite a simple calculation really. Don't forget to take into account the exceptional charges: Snow, wind... The slopier the roof, the less weight it caries (weight projection)

I put these beam 60cm apart as this is standard in the industry (in europe) and things come in multiple of this size for all the supplies (insulation, plasterboard...)

Make sure your beams are absolutely dead level otherwise, with time, it might not cary the weight properly and might start bending. To make sure we got it right, we draw each beam position using a clayed thread.

Don't bother putting the first and last one now as you will probably need to move them anyway to adjust to the tiling.

I put a 160 mil nail at every crossing.

Only messed up about five. Knots inthe wood can be really reallly hard.

Note how the beam are shapped at the top, I put the first beam, cut it with the circular saw and then used a template to report the correct angle on the remaining beams on the floor (better than balancing on top of the roof with electric and sharp equipement)... There is a nail on each side as well. Some people shape the beams so they rest on a larger surface. I didn't bother.

In order to check our calculation, we did a simultation at the bottom of the roof. Better find out now if soemthing is wrong... THis helped work out how much of the excess lenght was to be cut of the beams..

Just did the same kind of operation at the top.

Turns out the roof is resting a bit lower that the pevious one. We have to trin the wall. Big tools come in, a bit perillious, very dusty... Cut in location and then with hammer, get the bits off until you're satisfied that the wall won't get in your way.

We now need to put the underlay...

It's basically a sheet of cotton like material, that will cut winds and water from the inside. It come in 150cm width so we'll need several layer on each side be carefull to put it starting from the bottom, so that water running on top of it will end up outside and not on your bed !!

I cut the underly to the right size on the floor and set it up on the roof. It wasnt too windy so I was able to keep it in place with staples.

To hold the underlay in place and to make sure the tile aren't touching it (for best efficiency, there needs to be a air gap between the tiles and the underlay, roughly 50 mils.), We add some flattish pieces of wood on each vertical beam. They're nailed at the top and bottom, and will be nailed definitely at the next stage.

now we need to add the final piece of wood, the one that will support the tiles. Manufacturer's documentation specifies what size and spacing you should use... I suggest you stick to it obviously !!

The length of these pieces of wood comes in 4 meters, have the seems to be on the top of on one of the large beams. It a good idea to draw the position of each piece of wood with a chalked thread. don't bother cutting the beam at the right length, make just sure they overhang form the roof.

There again, don't bother putting the first and last one as they will need to be fitted to the tiles.

Last step...There, you need some help. You need to be at least 2 on the roof and one on the floor.

The best way is to actually throw the tiles... I know it sounds stupid, but it works out really well. We only broke four or five out of a thousand. Have a guy on the floor to open the packs and throw them one by one (he he) to a guy on the lower part of the roof. That guy then throws them to the guy on the higher part of the roof who lays them.

It's good to have the same guy to lay the tiles all the way as you can spot the difference between one layer and another. It's good as well to progress in the same fashion all the way, otherwise you can spot the difference again.

As you reach the edges, you can fit the missing bits of wood at exactlty the right position. You can also cut the excess overhanging wood.

You need to use half tiles on the edges, but it's quite straight forward.

I didn't bother nailing any of the tiles apart from the one on the edges as they're the ones holding all the others.

Cut the large beams so you've got a flat level surface at the top.

Nail another beam there and then put the round tile there. Nail them properly as they're holding all the other tiles.

Get yourself a well deserved beer.

overall, it took 2 week ends to do, with 2 people most of the time. I'd never done anything that serious DIY wise before and really enjoyed everything of it... I've done everything in that little place and could document it for you if you want.

I've been living this house for about 9 months now. And really enjoyed doing it over. It makes it really special to sleep under a roof that you've made with your own hands.

I've now started doing up a much bigger place... I get a real kick out of this...