Hi All

If you’ve been following my story, you will know it’s not my fault that we are building this particular house and the design has nothing to do with me. Neither do we benefit from being able to talk with the ‘conceptual’ architect as he appears to have disappeared off the face of the earth.

I do have the benefit of :

- 1 x experienced and competent builder
- 2 x experienced and competent architects
- 1 x experienced and competent structural engineer

Nevertheless, I seem to be getting whiffs of unease.

The issue is a 714 cm x 909 cm flat roof or ‘solarium’. This is bounded on one side (call it East) by the single storey salon (in which the nice fat trusses are now sitting) with a 4-sided 30% pitched roof and chimney. It is bounded on the South side by a garage. This is a separate structure built on a slightly lower ground level and has a 30% pitched roof on 1 south facing plane (on which the solar panels will be fitted). The apex of this roof is higher than the flat roof so it forms a barrier so you don’t fall off the flat roof and the garage wall creates a bit of privacy (easy access too to the solar panels). West side is open and fronts the house – iron railings. North side is the first floor part of the house with access to the solarium and then a bit looking into an inner courtyard – iron railings. The engineer’s drawing shows a 1% slope North to South ie from the house 1st floor towards the wall that constitutes part of the garage.

Gutters and drain pipes don’t exist in Provencale architecture, the roof line is supposed to extend far enough out from the building so the rain falls far away from the walls. My quote, however, provides for 4 gargoyle type things – although no one seems to know where they might go (not shown anywhere in the engineer’s drawings). Recently the builder was talking about getting the plumber to quote for something in zinc (although it was not clear to me what he had in mind) although he has now said he thinks we can do without.

I’ve bookmarked the ‘energy black hole’ thread and also been a close follower of the ‘lead’ thread. However, I thought my roof could do with a bit of looking on by the forum.

Issues to me are :

- I do not want leaks.
- I do not want puddles
- I do not want cascades
- I do not want huge energy losses

I would also like it to be :

- safe
- aesthetically pleasing
- low maintenance
- practical

If you look at the ‘trusses’ thread you can see pics of the flat roof.

See below for what is happening so far on the solarium / salon roof join ...

I haven’t seen pics yet of what the solarium / garage roof join looks like.

My question is : what sort of drainage should I be looking at and how will this work over the insulation and stone tiles that will be fitted over the concrete slab that has been built.

I think I would raise those trusses up two more courses of blocks. Then raise the flat roof up one block in height by building on top. This would allow you to form a one block deep trench against both the trussed roof and the garage.

I'll try and sketch something in a moment.

CWatters : I don't think they can raise the salon roof now they've started tiling it. There are 3 layers of these tiles to go on which raises the roof line somewhat. The solarium slab will be higher by the time they have the insulation and the stone tiles on top - assuming, of course, the insulation is going on top and not on the underside of the flat roof. There was some muttering about levels, so I do think the plan is to put the insulation on top. The same tiles are being used throughout - inside and outside. The first floor will have UFH but it goes into thinner insulation than on the ground floor.

Your drawing deploys the 4 gargoyles perfectly and explains the 'getting the plumber to quote for zinc'.

Should we consider sandwiching the concrete slab between insulation do you think?

Try with a .pdf ...

The little 'X' on the solarium is what was to have been a roof lantern - now ditched owing to costs.

What looks like Velux windows are supposed to be the solar panels on the 1-slope / lean to garage roof.

You say you still have two architects to hand. I would get them to talk you through the detail of how the interface between the pitched foor and the flat roof should be done.

Typically when you have a valley between two pitched roofs you form a little lead lined trench as I've described and extend the lead up the slope of each side to allow for build up of snow etc.

and another one ... so far we seem to have inside and outside at the same level.

Exactly what we thought. I was promised a staircase 6 weeks ago and they knocked together a ladder - which they are still using (seen poking above the parapet with a bit of thin rope attached). They appear to be using no lifting equipment - everything goes up and down that ladder!

What do you think they use the bananas for? (Last para of your wikipedia link).

I spoke to Archi 1 tonight. Still not satisfied about how this roof is going to work. What is worrying me now is that the last lot of photos show a complete salon roof and no chimney. I'm told again that the way they do things there is to complete everything and then smash it all up. Makes no sense at all.

CWatters:
You write: "If it were over here I'd be thinking of putting the insulation on the inside to stop cold bridging (eg to stop the concrete conducting the heat horizontally to the outside)."

This would not be a good move, if any cool or cold weather is expected.
Placing the insulation below would create a "Cold concrete-Decked Roof", which induces a serious risk of interstitial condensation. In Scotland they are outlawed, while in England they are severely frowned upon. Most commonly used in poorly-designed domestic extensions with a timber structure, where Building Regulations stipulate that such a Cold-decked roof should have 'full and adequate ventilation' - of each and every joist void(!)

In the case of a concrete deck, there is no ventilation possible/available, which will lead to gradual and cumulative condensation and water buildup in the concrete, as well as putting it outside the Bldg Regs.

Provided that it is properly-specified, the Warm-decked roof will prevent condensation in all but sauna conditions.
Another post follows . . . .

I guess you're right. I was looking at the pictures above and it appears the slab bridges any cavity there might be in the walls.

I'm still not getting any answers. Am I right to expect any?

My assumption has been that either individually, or collectively my consortium of builder, archi1, archi2 and structural engineer will have made a decision about what to do about drainage, waterproofing and insulating the solarium roof - bearing in mind very flat footed hints and the despatch of documents giving u-value calculations ...

Could it be that they are expecting me to tell them what to do? I hope not!

PS JackyR - they're calling the gargoylly jobs 'barbacanes' - very medieval sounding don't you think.

Just on the off chance that anyone can still muster the slightest interest in this dilemna - I've recently stood toe to toe with my professional team (except for the engineer, who went AWOL again) on the edge of something that resembled a first floor swimming pool.

(Rant commencing) : What I can't understand is, I haven't changed anything. It's not as if suddenly I've turned up and said "this is a nice space, let's not put a proper roof on it", it's been on the plans since dot, minus dot even as it's the design that 'came' with the building plot. Anyway a 'type' who I believe is going to be doing our external render was sur place and had a sketch on the back of an envelope, which, when it is written in neat will be rubber stamped by archi-2 but I'm still really no wiser or assured that I'm going to end up with a well insulated, leak free flat roof that drains well and appropriately. An added concern is how to fix the guard rail so it doesn't wobble but doesn't compromise the sealant.

A couple of plombiers who happened to be sur place at the same time, obliged by knocking out a bit of agglo to release the build up and create a waterfall. Observing the mix of water + electrically operated angle grinder was excruciating ...

Pleased someone else's structural engineer has gone awol! (maybe it's a strategy taught at college)

Best of luck to you Mrs Whitecat!

Sally

PS Have you looked at Roofkrete for your flat roof?

On that note can I recommend some cakes.. http://www.cakes-direct.co.uk/ They claim to have delivered to ships at sea :-)