Detail design

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, I’ve finished everything for the basement. That was fairly straightforward since it’s all made of concrete. There’s one question about the type of concrete, though. The structural engineer suggested using green concrete instead of conventional B25 concrete.

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

Hanna: Yes, I’m quite sure Joe White knows what he’s talking about. It’s 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 he’s sure it’s the right thing to do, let’s do that. It’ll be in line with the planted roof and the other green solutions. So what about the other details?

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

Tim: Yes, sure. Let’s see – you’ve 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, you’ve put sheathing with a waterproof breather membrane, then battens, counter battens and the cladding.

Hanna: So, it’s 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, don’t we? It shouldn’t really be a problem for electricity, but I’m 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, I’ll do that. But just going back to the outside – 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: You’re right. I don’t see any reason why that shouldn’t work. So, make that phone call and then change the drawings accordingly. Come and see me if you’ve got any more questions, and ask Jane to give you a hand today and tomorrow. Together, you’ll get the bills of quantities sorted in no time.

Hanna: Okay. Thanks for your help.