Flat Roofs

[Smurf1976]

"Flat" roofs (the ones with a low pitch, not literally flat, and high parapet (think that's the term) around the outside so you can't see the roof when standing on the ground) aren't common where I live and I've never had much to do with them.

But I'm planning to move in the next few months and have noticed quite a few otherwise attractive houses for sale with such roofs in the area I am looking to buy in.

Can anyone tell me what (if any) are the disadvantages of this type of roof?

Also, how far is the gap between the underside of the roof and the actual ceiling? I'm assuming it's far too close to crawl through? If so, then how difficult is removing a section of the roof to gain access (to install some wiring, add insulation or any other reason) to the ceiling space? One web site I checked says you can't remove part in the middle without taking literally half the roof off.

Anything else about such roofs I ought to know? Presumably any decent building inspector will determine if it's waterproof. But any other issues? Are they any more or less likely than a pitched roof to come off in very strong winds?

As I said, I don't know anything about these roofs as they just aren't that common where I live at the moment and I've always lived in houses with normally pitched roofs.

[jackson8]

depends on climate where house is if very hot it would be like living under a hot tin roof literally
normal ceiling space would be between 6 to 10 inches maybe less so there is no crawl access
as to removing roofing area will depend on type of cladding be it tiles or corro iron both can be taken of in small areas but bit of a hassle
also flat roofs dont insulate noise very well if you like the sound of rain on the roof then i suppose okay

[tasmanian]

smurf,

ive worked on these type of roof,s a few times.

the ones ive ever had to deal with you cant crawl through you do have to lift the roof.not overly difficult though a claw hammer to pull the sections apart.not a big job at all.
they can be lifted in the middle as each section is roughly 400mm.so to do electrical wiring its a matter of lifting one section poking the wire across a few metres and then lifting another section.basically just like a normal corrugated roof just the sections are smaller.

ive never done insulation but it would be possible not as easy as a normal pitched roof but just abit more time consuming.definetely could be done though

im no expert with these but ive never heard of any water problems as generally they dont have nails or screws to hold them down each section is basically just clipped to the next piece.

personally if you like the house i wouldnt let a flat roof stop you.

just a few ideas but im no builder so maybe there are disadvantages im not aware of but really cant see any major ones.

good luck with it
cheers

[tech/a]

7.5 degrees is normally the minimum pitch.
Having one in the new Home I'm building.
Have them in a few apartments of ours.
There is enough space to crawl around for wiring.
Good sized Box gutters was one hint Ive recieved.
Un aware of any problems.
Normally chosen to help overcome height restrictions.
Reading above must be different in some states.
The pitch on the roof's I'm talking about you can get under.
Flat ones obviously you'll have to do as Tasmanian says.

[jtb]

My games room has a hidden skillion roof as described and the long line clip lock sheet (10m) is a real pain in the a$$ to try and access.

Yes big box gutter is definitely a must.

Thankfully I can access the wiring from inside as it has 5" foam textured panels as the ceiling, supported in the steel H beams.

Apparently its circa 1975.

As already mentioned its a bit hotter than a conventional insulated roof, but definately water proof due to lack of holes.

[Freeballinginawetsuit]

Ideal for a new building IMO. No need for trusses or a ridge & no wasted cavity space. You could basically gain your load bearing support either from an insitu RHS/RSJ setup on your external posts with the 'in fill walls doing nothing structurally'.

Or use the standard DB or tilt panel setup with those load bearing.

Flat roofs also offer a raked ceiling effect when pitched North/South, a good set of electrical plans will pin point what sheets or tiles you need to lift to gain wiring access so no hassle really from that aspect.

Only way to build IMO, I built one and would never live in a pitched roof house again!.

[Flying Fish]

Whats the best insulation for these flat roofs? Aluminium foil, is it effective in hot places thanks

[Smurf1976]

Thanks everyone for the info.

For some reason I had the impression that flat roofs were something to avoid but it seems there isn't a problem after all. So that gives me some more houses to choose from...

[moXJO]

Minimum pitch for corrugated is 5 degrees. Trimdek profile goes down to 2 degrees and kliplock will go down to 1 degree.Insulation such as anticon (fibreglass wool with foil back,comes in different thickness)will take down the noise and recommended cause it will get damn hot otherwise.If its kliplock on there now it will be a bugger to get off theres a trick to it though.

[purple]

There are generally 2 types of Flat Roofs:
- the roof is finished as a concrete slab (you can get up on these kinds of roofs stand on them, have a party on it and use it as a very large balcony)
- the roof is finished as a very low pitch metal cladding (this functions as a roof)

which is the one you're looking at?

whether or not it is waterproof depends on the workmanship. you could have a normal pitch roof and still have it leak rain water.

Quote: Originally Posted by jackson8 depends on climate where house is if very hot it would be like living under a hot tin roof literally

[Stan 101]

Smurf, shallow pitched roofs can be very effective visually. They can also be an engineering nightmare. If the house has a parapet, you will most probably have a box gutter formed by the roof truss or rafter/purlin. Roof trusses can be a minimum of 3 degrees. 3 degree slope is required for run off on a sheet roof. Tile / shingle roofs need to be sarked at 15 degrees and under and I do not recommend them at a pitch lower than that, though it does happen.

some things to look for:

1. The box gutter's volume is vitally important in a high rain / snow area. Check for signs of overflow. Check the ceiling lines directly under the box gutter for deflection and/or plaster cracking. If you PM me i can send you more info I why this is so important. It can be hiding other structural issues. Also a good chance to knock the price down after the inspection.
2. Is the box gutter itself in good repair?. Is it a snug fit and well flashed/sealed? Remember a box gutter leaking is not easily detected when it first starts and is expensive to repair.
3. Is the parapet braced to stop it flapping in the wind? How is it braced?

This style of building is so common especially in the Gold Coast region. They can look very stylish with a good finish. Just need to be engineered correctly, which unfortunately does not happen as often as one would expect. As I metioned, I'll go into detail if you need via PM.

happy buying