Flat Roof Patios in Wanneroo

Nearly every project home built in Wanneroo over the past 15 years came with an alfresco tucked under the main roof. It is usually about three metres deep, it is shaded, and it is not big enough for the table people actually own.

Extending it is the common brief. A flat roof does this better than a pitched one because it can run out from the existing alfresco at a shallow fall without the ceiling dropping to head height at the far end.

Where it gets technical is the junction. The new roof has to pick up on the existing alfresco beam or wall, keep the water moving away from the house, and not create a dead spot where two falls meet. Get that wrong and you have built a puddle.

Many newer Wanneroo estates carry developer design guidelines registered against the title, and they run in parallel to the council approval. They can have something to say about roof materials, colours, how visible a structure is from the street, and boundary treatment.

That is a second approval, not an alternative to the first. A patio can be entirely acceptable to the City of Wanneroo and still breach a covenant on the title, and the covenant is a private legal obligation the council does not police.

It is worth checking early. Colour restrictions in particular can decide the whole look of the patio, and it is a poor time to find out once the sheet has been ordered.

Wind classification depends heavily on shielding, which is a formal way of saying how much stuff is upwind of you slowing the air down. An established suburb full of two-storey homes and mature tuarts provides plenty. A half-built estate in Eglinton provides almost none.

That is why two identical houses can carry different ratings. The same patio plan, on the same slab dimensions, may need bigger posts and deeper footings in Alkimos than it does in Landsdale.

The coastal strip compounds it. Yanchep, Two Rocks, Quinns Rocks and Mindarie combine open exposure with salt air, and both the structural spec and the steel grade move together.

Western Wanneroo is dune country. Pale coastal sand, limestone in places, quick drainage and poor lateral support for a post, much like the coastal parts of Joondalup.

Inland is another story. Around the Wanneroo townsite, Sinagra and the old market garden land near the lake systems, the ground can carry organic and peaty layers left by wetlands, and it can hold water long after a storm has passed.

That difference decides the soakwell design. Sand takes what you give it. Damp organic ground does not, and the array has to be bigger, shallower or repositioned to somewhere the water will actually go.

The building permit comes first and it is not optional. A patio is Class 10a work, so the City of Wanneroo needs a permit application before construction, supported by a site plan, elevations, engineering for the assessed wind classification and a stormwater plan.

As with other WA councils, Class 10a can go in as an uncertified application for the council to assess, or as a certified application with a certificate of design compliance already attached from a registered building surveyor.

On small lots the planning side is more likely to come into it. Setbacks to a side boundary, the amount of open space left on the block, and whether the required outdoor living area is still uncovered are the three questions that come up most often on a 350 square metre Wanneroo lot.

On a narrow block the honest constraint is not the roof, it is where a post can stand. Fence lines, meter boxes, air conditioning condensers and the paved path down the side all compete for the same ground.

A flat roof helps because it can span further without gaining height. Where a pitched structure would need an intermediate post to keep the ridge sensible, a beam sized for the span can carry the same distance and leave the paving clear.

It also keeps the roof under the eaves line of a two-storey neighbour, which on a Wanneroo estate lot is usually only a few metres away. Less bulk at the boundary, fewer objections, and more daylight left in both yards.