I have an area 8.5m long by 3.6m wide that I need to put a roof on

If there are any "builders" (ex-taxidrivers/postmen/mechanics/librarian cum builder will do) then can you answer a couple of simple questions -

1. How many vigas will I require?

2. What do you call the big shaped clay bricks that fit in between vigas?

3. How many of No.2 will I require?

Cheers.

The spacing and therefore number of the vigas depends on the loading! Is this a flat roof or a pitched roof? Roof terrace or not? Anything going on the roof (water deposito, stairs...)? Type of roof tiles/other finish? Ceiling finish? Insulation required?

Between vigas you have a choice of materials - bovedillas (concrete, terracotta or polystyrene), terracotta rasillones etc.

The number of these reqd will obviously depend on the spacing of the vigas and the size of the bovedilla/rasillone (they vary)!

(ps not lecturing, but for a new roof you need a major works licence and therefore an architect who should be doing the design for you!)

Thanks Hillbilly, but I'm just trying to cover an area out the back to give us a bit of shade. I've built a wall at one end and now just need to put vigas over the top. One end of the vigas will be cemented into the wall of the house, the other resting on my new wall.

I may want to use it as a roof terrace in the future which is why I'm using vigas instead of tiling it. I thought the terracotta clay type infill things would be the right thing.

I probably should get a licence for this but it seems that everyone else around us just builds whatever they like - new houses, extensions, pools, etc. so I'm just going to risk it. If I get fined then so be it.

If you assume vigas @ 700mm centres then, you will need 13 of them (which will give you 8.4 m width in total, if you can live with the covered area being 100mm less than 8.5m). I'm assuming that you're spanning the 3.6m length, not the 8.5m length!!!!!
The vigas themselves need a bearing of 150mm at either end minimum.
The bovedillas ceramicas are usually 250mm long and so you will need 15no between each pair of vigas so a total of 180no. You will need to check on the size of the bovedillas though because, as I say, they do vary from manufacturer to manufacturer.
Disclaimer: The above is no substitute for employing an architect etc etc!!!!

Thanks Hillbilly, I appreciate your disclaimer.

I'm trying to do this little project on the cheap over several months and can't afford to employ an architect for such a piddly little job.

I've ordered the vigas and bovidillos - should be here this pm.

I'm planning on chiselling holes in the wall of the house to stick one end of the vigas into - you suggest at least 150mm for them?
The other end of the viga will sit on another viga which is placed perpendicular and will overhang by at least 300mm.
Does this sound safe enough?

you do know that by carrying out this work yourself....once finished....... you will be a fully qualified "builder"

Billgates, that should be fine. I hope you realise how heavy the vigas are going to be! I assume that the wall you've built has some lateral restraint and isn't free standing?

By your explanation I am visualizing this other viga has a span under it , otherwise surely they would sit on the blocks ?

I have just re-read your op and like hillybilly says that is a lot of weight for a free standing wall, especially if its going to be a roof terrace also.

As I read it (!), he is going to place a viga beneath and at right angles to the new roof vigas and sitting directly on top of the new block (?) wall...not sure why as, yes, normally the vigas would bear directly on the blocks...
Does the new wall have an opening(s) in it? Have you actually built piers (columns) or a solid wall?

I've constructed pillars which have their foundations at least 3 feet deep under a 4 inch concrete slab. The pillars are spanned by arches constructed from concrete blocks.
I don't want any load on the arches themselves so I have laid vigas across them with the load taken up by the pillars only.
I have now placed 4m vigas spanning the gap from the house to the new wall/arches. These vigas are set at least 130mm into the house wall and the other end sits on top of the wall/arch vigas with an overhang of about 200mm.

Blimey, those vigas are heavy. Have placed just four so far, just another 9 to go.

Spain, I do realise that if this little project works out ok then I could quite confidently set myself up as a builder and my particular background (computer programmer) would perfectly qualify me to construct multi-story houses.

Can I offer you some advice on carrying heavy bricks, bags of sand, cement etc, having been doing it myself for what seems like a month.


Get someone else to do it ... you'll get a bad back