Building Standards: Roof Tiles and Insulation

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For those folks thinking of buying or building here's a few lengthy posts on roof tiles and insulation, roof flashings, and brickwork  These posts comment on what's normal, in say the UK, and what done here in Malaysia. Other points of view are welcomed.

Roof Tiles and Insulation

Just like brickwork, there’s not a lot of roof tile types to choose from. And from what I’ve see there’s not much available in the way of tiles for hips, valleys and anything other than a standard ridge tile.

Roof tiles are manufactured to certain specifications for roof pitch, overlap of tiles and tile batten spacings. There’s not much flexibility here but what can be stretched is the spacing of roof rafters/trusses. The norm that I’m familiar with is rafter spacings of about 450mm to 600mm. Here they tend to start  beyond 600mm and go up to 900mm. Again, it’s very thin construction and all the roof timbers are pretty rough bits of wood.

There’s no sorting-out of the timber so if a 15 foot length of  3 x 1 is warped it’s still used. And the timber is certainly not tanalised or treated for rot and termites.

The most commonly used roof tile is a lightweight concrete interlocking tile. It’s so common that roofs in Malaysia now look much the same, everywhere. It’s only a matter of different roof shapes and tile colour. White is best for heat reflection but isn’t made so the lightest available colour is next best.

Tiles have a nail hole (or 2) in the top edge. In Malaysia, the tiles are usually just laid down, not nailed. It’s the same for ridge tiles and for ridge tiles used for hips and gable ends. It’s all loose construction. The ridge tiles seldom have the usual mortar bedding. (50/50 chance)

I have experience of this in my rented house. The monkeys play on the roof, and every couple of months or so I go up to put back the ridge tiles – just lay them down slightly overlapping. It’s not that the mortar bed has crumpled away, it wasn’t there to begin with, and the main roof tiles are the same – no fixings.

In my case there’s nothing between the tiles and the ceiling. Again, this is normal. Some roofs have a layer of aluminium composite sheet below the tiles to act as a reflective insulation layer and also to trap water that gets through the tile joints. This layer is pretty thin stuff as the good stuff (the proprietary name is Systillation) is expensive. To make the thin stuff go further the overlaps between sheets are reduced, and they’re not taped down.

Quite often a Tiler will put his foot through it, or drop a tile etc. or it rains so the foil sags. It’s not much of an effective, continuous barrier to either heat or rainwater.

If you’re checking out a property or having one built ask about tile nails, mortar beds, quality composite foil sheet, and clumsy tilers. And check the rafter/truss spacing, and if the timber has been treated. At least you’ll know what you’re getting, or not getting.

regards, Scott

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Flashings

Where the tiled roof hits another bit of roof there’s a valley. Good quality tiling includes valley tiles. I’ve never seen these in Malaysia. Instead, and generally everywhere else, it’s zinc sheet.

Zinc is OK for valleys if there are timber boards underneath it to give support, and if it is wide enough to run up behind the tiles and be nailed into the rafters. Again, this doesn’t happen in Malaysia. The zinc valley gutters are minimum width, not supported on boards and seldom nailed.

Zinc is also used as flashing for where the tiles run-up against a parapet or higher wall. The norm is for the zinc to be cut and shaped and tucked into the brickwork mortar joints and then stepped-down as the slope of the roof runs down alongside the wall. In fact, in really good construction 2 layers of zinc are used. A lower layer under the tiles (called a “soaker”) and a top covering layer.

In Malaysia it isn’t done this way. What happens is that the roof is laid with tiles except for the bit of roof next to the parapet or vertical wall. The external sand & cement plastering (render) then goes on. As this is a messy job quite a bit of render drops down onto the roof timbers and through the foil insulation. If there’s no foil then it drops onto the ceiling boards.

When the wall has been externally rendered, the final tiles are laid. The zinc flashing is then bent into a “Z” shape with the lower bit over the tiles, and the top bit pushed into a slot cut into the render. It’s not really wonderful detailing.

It makes me think that the best roof is one that doesn’t have any valleys, hips, and odd bits of roof tacked-on here and there.  Pretty similar to traditional Malay style in fact.

A roof slope that goes up one side and down the other doesn’t need zinc flashings.

regards, Scott

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Sorry to mess around with this section but I think it's easier to split into 2, as each post may get lengthy.

Here's some photos of roof tiles that are very commonly available in Malaysia, and if you're buying from a developer then you'll be getting something very similar in size, shape and texture, although colours will vary.

All the tiles are lightweight interlocking concrete, and have nail holes.

I think that I may have worked-out why the tiles are seldom nailed down. It's probably because the tile battens (the horizontal timber strips that the top edge of the tile rests on) are of a small rectangular section and they span over 600mm between rafters (supports). So nailing through these battens would bust them. If there are any contractors out there I don't mind being corrected on this.

My own quick motorbike survey around my area shows about a 50/50 chance of having the ridge and hip tiles properly bedded on mortar, rather than laid loose.

First Photo	Blue ridge tiles
Next Photo	Blue flat interlocking tiles
Next Photo	Red ridge tiles
Bottom Photo	Red ridge/hip junction, hip end and curved interlocking tiles

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can't believe they get away without cementing the ridge tiles, how come no one has been killed with the strong winds blowing them off ?
i have also emailed instructions to my builder to make sure he does the roof right. I had never thought to ask him before, about the tiles etc as i assumed it would be built correctly for safety. Good job the architect is also keeping an eye on things for me.
john

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hi, John,

I remember reading an article in the Star. It was about 3 weeks ago following a couple of days of high winds. The article showed a block of flats with roof tiles lying around. One of the residents complained that roof tiles were always blowing-off.

Luckily no-one was hurt.

Traditionally ridge and hip tiles are bedded in mortar. Older buildings here in Perak are finished like this, and the construction looks good after many years.

On some new houses that I saw last week, the hip tiles rested on zinc sheet. I think that this is dodgy, and it's probably caused by the poor tile laying which gives a big gap between the 2 roof slopes that meet at the hip. A big gap means that there's nowhere for the mortar bed. Mortar will just fall through the roof. It can all be solved with just a slight increase in care and attention, it's not rocket science after all.

regards, Scott

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It is rare to get the prolonged very high winds here that one can experience in the UK, and this may be the reason for lack of concern for 'fixing' the tiles. However just before a storm winds can be very strong and gusting albeit for a brief period, and hence a sheet can fly and tiles do shift.

As mentioned before rainbow, thing may not turn out the way you anticipate unless your architect is extremely well briefed and absolute clear on ALL of your requirements and specs.

A friend of mine has had the builder remove the whole roof as the support beams visible over the balcony area were unevenly spaced. He also had a number of internal wall knocked down and rebuilt they didn't measure up as properly square or rectangular. Shoddy work indeed...and it happens all the time everywhere here!

If possible you should make regular 'inspection checks', just to be on the safe side.

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thanks for the concern but my architect is visiting the site 4 times a week & sending progress pictures by email each time PLUS the builders have agreed to nail every tile down, not just every 3rd row as he was going to do.
i think i have one of the best architects around & also good builders. So far i am very pleased with the progress & attention to detail.
Only time will tell of course.
john

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Really glad to hear that the works are progressing well. Your architect is certainly attentive. One site visit per week is the architectural norm, at least in the UK.

regards, Scott