Alfresco/Outdoor room - concrete by builder or not?

Hello

Our builder does not concrete the floor of the alfresco/outdoor room in standard (same for the porch). However we can do it as an option and would be part of the house slab then (cost is ~ $135/sqm).

What would be the pros and cons of doing this by the builder versus after handover?

If we want a timber deck is it better not to have concrete under?

Thanks in advance for your help
DKP.

It all depends on you if you want the concrete included in the slab, our engineers recommended we go with including it in the slab as they feel that strip footings for alfresco areas would lead to problems down the track, it cost us approx $600 extra to include which we have.

I know some ppl think its a waste if you are decking, but I dont know when we can afford to deck, so at least in the meantime we have concrete there and not dirt/mud.

i reckon its still cheaper to build a deck over concrete then on bearers and joist.

Even if you have to pay for the concrete

My builder included the concrete slab to our alfresco, and their reasonings behind it was exactly as ring09 suggested. The alfresco cost a whopping $10K, but it was great to have just the concrete out there to use before we decked the area. (except the concrete dust coming in the house from feet was a real pain!)

One thing we did find difficult, was making sure all the joists for the decking were level, as the slab was not in places, so the joists bounced around a bit. If there wasn't a slab there to start off with, it may have been easier to just dig the posts into the ground and level them that way...but you live and learn! Being a complete DIY job, there may have been an easier way to level them out instead of packing and dyna bolts...but we didn't know! We could have used leveling compound, but that's expensive too.

Also, having a concrete slab underneath, the water can sit ontop of it underneath the deck for longer than what would be absorbed by the ground. Also our deck is pretty much completely enclosed underneath because of the slab and water doesn't 'freely' drain away. It's only been down for a couple of months, and hasn't had much use now it's winter. The water used to pool near the back door as the slab wasn't level...but I can't tell you if it does now..must check next time it rains and I'm home!

The deck cost us just over $2K and 6 weekends...not sure how much a deck of the same size (7 x 4m) would cost without the concrete and on posts.

Long term, I cannot say what is better...I'll let you know in 5 years time how it's holding up! It was a pain to get it level and not 'bouncing' for complete DIYers!

Stormy... the bounce comes from the joists. Would suggest you had them a little closer together- 450 centres is the max. Assuming you've used 45mm joists, that means about 400mm between joists is enough.

I reckon even if we had put them closer (they are 450 centres and 140 x 45), then they still would have bounced around anyway, as the joists were not completely straight, and the slab was not completely flat, leading to the 'bounce'! Hence the packing, planing and dyna bolting!



It hasn't moved, and I don't notice the 'bounce'....but then it's freezing outside, and we haven't used it much yet! (Too much else to do!).

Anyway, it will be interesting to see how it weathers over the years with the slab directly underneath instead of soil.

The majority of our alfresco was included in our price, we added an extra 2m width by the length included in the house for $950. The credit to exclude the existing concrete was not worth the value. From the research I did the advantage was in the construction as part of the slab. Less likely to separate from the body of the house. It would also be included in the builders warranty period which would not be included if we had it done through an external concretor. It can become messy if we tile over the area but our budget may only allow for paving or painting over the concrete for the first several years after construction anyway.

One other thing to consider is if you want a different surface.

Tiles straight over a slab would work either way, same with polished concrete.

But say you wanted exposed aggregate, post handover would be the only option.