Cold nights are coming and your slab will not wait. Will it?

Nobody can name one date that works every year, and anyone who does is guessing. What you can do is learn what makes a late pour risky, check the Syracuse numbers, and put a plan in writing. Then you decide with facts instead of a salesperson's deadline.

A pour on a mild afternoon can still go wrong. Fresh concrete stays vulnerable for days, and it is the temperature during that window that counts. In ACI 306R-16, cold weather means air at or expected to drop under 40F at any point in the protection period, and not just during the pour itself.

So the real question is this: what will the nights do in the days after you pour? A pour on a warm Tuesday that meets three chilly nights still counts as cold weather, whatever noon looked like.

Ask any contractor you speak to what the forecast shows for the nights after the planned date, and ask what they will do if it drops. Write the answer into the scope.

Here are the typical monthly counts of days with a low at or under 40F, from NOAA's 1991 to 2020 Syracuse normals. In September it is 2.2. In October it climbs to 13.9. In November it is 24.2, and in December 30.3.

Spring counts too. April averages 20.8 such days and May 7.1.

Cold-weather pour rules start to apply by October, and they apply again in spring: Syracuse still averages 7.1 nights at or below 40F in May. Ask your contractor which month the pour falls in and what the plan is if the forecast turns.

Use these as a guide to timing, and not as a promise. Ask your contractor for a month, and ask them how that month compares with the numbers above. An October pour is not forbidden, but it asks for more protection than a pour in a warm month.

People mix these up, so keep them apart. The protection period is how long fresh concrete must be shielded from cold. For normal-set concrete, ACI 306R-16 gives 2 days if it carries no load and is not exposed, 3 days if it carries no load but is exposed, and 6 days with a partial load and exposure.

Curing is separate. NRMCA says curing should begin right after placement and finishing and typically lasts 3 to 7 days, with a gradual finish to drying.

Do not accept a single number without asking which one it is. Ask your contractor to state the protection period and the curing period separately, in days, and to say who is responsible for covering the slab and for how long.

New concrete holds a lot of water. ACI 306R-16 says it begins past critical saturation, where a single freeze can hurt it, and drops under that line only once it has built strength and dried somewhat.

NRMCA puts the freezing point of fresh concrete near 25F, and says a frozen slab can end up with less than half of its potential strength and poor durability.

NRMCA also urges care with outdoor pours in late fall, winter and early spring, when a still-wet slab may freeze soon after it goes down. Ask your contractor how they plan to keep a slab from freezing wet, and what they would do on a night that turns colder than forecast.

If you decide to pour in a cold-leaning month, ask for these in writing. You are looking for a plan with specific actions, not a general promise.

• The mix: air-entrained concrete, with the air content named.
• The ground: no concrete placed on frozen subgrade, and snow and ice cleared first, which NRMCA lists among its winter rules.
• The cover: how the slab will be insulated or covered, and for how many days.
• The call: who decides to postpone if the forecast turns, and what happens to the date.
• The first winter: sand for traction, and no de-icer on the new work.

Read that list again before you sign. A contractor who agrees to it all in writing has told you something useful. One who dodges the list has told you something too.

A slab poured in a good month still has to get through its first winter. For the first winter, NRMCA says keep de-icer off and spread clean sand for grip. It also warns that some de-icers, including magnesium-based ones, are aggressive toward concrete.

This matters for a late pour, because an early freeze may come before the slab has had much time to dry out. Around 84 days a year bring a swing above and below freezing in Syracuse, so a new slab faces many cycles before spring.

So tell everyone in your household that the new slab gets sand, and ask your contractor to leave a note with the product to use. If you take one thing from this guide, make it that: protect the slab, and keep salt off it for the first winter.

Waiting is sometimes the better call. If your slab is cracked but safe, a spring pour avoids the cold nights altogether. The cold-night count drops through May.

If waiting means a trip hazard or a failing step, ask your contractor for a temporary fix that stops the danger without committing to a cold-month pour. Ask what it costs, and whether it will have to be removed.

You can also use the wait. Use the months before spring to collect quotes, ask for written scopes and compare mix, month and protection answers. A good contractor will not mind that you are planning.

A line like "we can only do it this week" is a reason to slow down. A repair that ignores the nights fails the way the original did.

1. What do the nights look like in the days after the planned pour date?
2. What is the protection period, in days, and how will the slab be covered?
3. How many days of curing does the plan call for?
4. Is the concrete air-entrained, and what air content is written in the scope?
5. What happens to the date if the forecast turns cold?
6. What do I use for traction and ice on the new slab this winter?

We do not pour concrete, and we are not the contractor. We can help you work out whether to go now or wait, then introduce you to an independent local contractor to quote the job. Tell us about your slab and when you hoped to pour.