Site Manager Jussi Lahti of SRV Construction Ltd. is a veteran of many Finnish winter projects. He has a strong opinion on the subject and doesn’t really look forward to winter.
“I think that you should avoid building in winter. It’s a pain regardless of the project phase.”
But the reality is that, in many parts of the globe winter takes up to 6 months and building in wintertime is inevitable.
So, here are Lahti’s tips on how to beat winter and still achieve impeccable results.
1. Keep everything clear of snow and don’t let anything freeze
Sounds simple, but it’s actually the most critical thing.
If the excavation freezes, it needs to be melted again as you cannot cast concrete on frozen soil. It all costs a lot.
“Keeping things unfrozen is the reason why you can expect to pay up to 20% more in winter compared to building in summer months.”
To illustrate the fact, Lahti recounts what happened some years ago when they couldn’t use district heating on site as planned.
“We had to rent three additional oil heater containers, which made a huge, unexpected hole in the budget,” he recalls.
2. Choose the right building method
The jury is still out on the building methods as both cast-in-situ and precast have their virtues and challenges. Jussi Lahti has no clear favorite.
“Of course, building with precast is quicker and you can get longer spans than with cast-in-place. But I have to admit that I love the smell of fresh concrete in the morning. And casting concrete is always manly,” Lahti laughs.
But he’s quick to remind the cast-in-place advocates that concrete always has a price premium in winter.
“Compared to summer, concrete has to be much warmer when poured. The temperature can be as high as 35 degrees Celsius (95 Fahrenheit). You need to have a higher strength class to facilitate faster reaction and more heat to avoid freezing,” Lahti says.
If concrete freezes before a compressive strength of around 500 psi is attained, it can lose up to 50% of its ultimate strength.
3. What’s out for the joints
“If you connect beams with Gerber joints, it means that there is always a beam between the column joints. This makes for same kind of challenges as with walls and small amounts of mortar.”
Lahti says that with hollow-core slabs you have to make sure that the drainage holes aren’t blocked – otherwise meltwater can fill the slab and split it when it freezes.
“That’s something you definitely don’t want to fix.”
4. Listen to the people on site
Finally, Jussi Lahti has a free tip for all the parties involved in designing and scheduling the projects in the warmth of the office.
“Listen to the guys on site. With their experience, you can avoid many of the pitfalls of winter building.”