Detail design

Hanna, one of Timís employees, is preparing plans, thinking about details and doing the quantity take-off for the bills of quantities. Listen to the conversation between Tim and Hanna.

Tim: Hanna, how are you doing with the quantities? We really need to get the bills of quantities ready for printing and then sending out on Friday.

Hanna: Well, Iíve finished everything for the basement. That was fairly straightforward since itís all made of concrete. Thereís one question about the type of concrete, though. The structural engineer suggested using green concrete instead of conventional B25 concrete.

Tim: Yes, Iíve heard of green concrete, but is it still sufficiently load-bearing and will it set as quickly as conventional concrete?

Hanna: Yes, Iím quite sure Joe White knows what heís talking about. Itís the newest trend and the more environmentally friendly solution. They replace some of the Portland cement with fly ash, which is a waste product from steel production.

Tim: Okay, if heís sure itís the right thing to do, letís do that. Itíll be in line with the planted roof and the other green solutions. So what about the other details?

Hanna: Well, Iím having a bit of trouble with the exterior walls. The total wall structure with insulation and the timber cladding adds up to 42 cm. Iím not sure whether we can save a few centimetres here or there. Could you possibly take a look?

Tim: Yes, sure. Letís see Ė youíve got plasterboard on the inside, then a substructure of battens and counter battens, then comes the load-bearing structure with the timber I sections; on the outside, youíve put sheathing with a waterproof breather membrane, then battens, counter battens and the cladding.

Hanna: So, itís in line with what the carpenter said, but I do wonder whether we could just work with one layer of battens inside and out?

Tim: Yes, that would save us almost 5 centimetres. On the other hand, we need the depth inside for the installations, donít we? It shouldnít really be a problem for electricity, but Iím not sure about plumbing and heating. Could you take another look at the plans, and possibly give the building services engineer, Frank Miller, a ring. Ask him how much space he needs in the exterior walls.

Hanna: Okay, Iíll do that. But just going back to the outside Ė can we make do with a narrower substructure there? I could remove the horizontal ones. The vertical ones will allow for ventilation and provide the substructure for the horizontal cladding.

Tim: Youíre right. I donít see any reason why that shouldnít work. So, make that phone call and then change the drawings accordingly. Come and see me if youíve got any more questions, and ask Jane to give you a hand today and tomorrow. Together, youíll get the bills of quantities sorted in no time.

Hanna: Okay. Thanks for your help.

Now take a look at the detail drawing for the wall structure.

1241 mm timber I-beam
2 insect mesh
3 241 mm cellulose insulation
4 12.5 mm gypsum fibreboard
5 16 mm sheathing, wood fibreboard
6 24 mm weatherboarding
7 30 mm batten/cavity
8 18 mm sheathing, OSB board
9 insulated services cavity

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