Winter extension risks

francohoops

We're planning a sizeable extension (part single/part double). We've found a good builder and plan was to start in Feb/March of next year. Builder is now saying that they can start just after Xmas. My concern is that given the likely cold weather we may have issues with concrete setting etc. whilst I'm keen for the works to be done, I don't wants cracks appearing in the walls in 5 years as the builder rushed the concrete pour. Any advice? Am I over thinking this?

Furts

You are correct in having concerns and these are real. However nobody can change the weather. What you have to do is manage your builder. It is your duty anyway, but in winter you will need to think about starting and finishing times, welfare and clothes drying facilities. getting a max min thermometer, having adequate hessian, sheeting, foam and so on. You will need to plan ahead with weather forecasts influencing work, and accept your schedule/programme of work is likely to be slower or delayed. It is not just concrete, it is mortar and hence walls, it is icy roofs and even sealants not be any good at say below 5 degrees. Basically following the ethos of the CDM regs, then adding in supervision and inspection. If you are not confident in all this you should give consideration to professional help.

All this will be influenced by your location, exposure and altitude. So there is an element of risk analysis here.

Do not expect your builder to be concerned with all this. The opposite can be true because corners can be cut to compensate for delays caused by the weather, short working days and so on. Plus do not expect your builder to welcome you getting professional help. However, this could be the reason your job has been brought forward - somebody else does not want the winter working!

LandyAndy

I had a sizeable extension built two winters ago. The works ran from just before Christmas through to the beginning of April with most of the major construction works being done in January and February. It was overseen by my architect but was effectively overseen by my builder who was excellent in organising materials and sub contracted labour. Because I only work mornings I was able to build a good relationship with the main subbies involved and made sure to chat to them about how the work was progressing etc. The builder was on site most days so it was easy to keep up with progress and make adjustments when necessary. They all seemed well versed in what could or could not be done in certain weather conditions.

Two years on, the construction is still looking perfect and being built in winter appears not to have affected the quality.

I ought to say that, as I am in southern England, frost was rarely a problem but rain was.

I know it isn't easy if you are at work all day but I would try and take a detailed interest in the works as they progress and ask about things. I found the builder/subbies quite happy to answer questions about what was being done and why.

It is a really interesting process to watch and you learn a lot (although I did already have some basic understanding of what was involved).

EachPenny

As Furts says. The main issues with winter working are the weather and shorter working days, although for a small extension there are ways of getting around both those problems. Most people would avoid groundworks during wet or winter weather because of the mess it makes, and if in poorly draining soil the problem of keeping excavations empty of standing water.

If your only concern is about the strength of the concrete then don't be. Concrete undergoes a strongly exothermic reaction as it sets and needs water for the process to complete. The strongest concrete is formed when the reactions are slowed and a drier mix is placed in an environment where additional water is available to keep the reactions going. So long as the surface is protected from frost the cold weather is actually good for concrete. In the summer the heat from the reaction can cause micro-cracking and if it dries out too quickly then it won't gain full-strength. In large civil engineering pours chilling equipment or dry ice is sometimes used to reduce the temperature to prevent cracking.

So if the builder can be managed to ensure shortcuts aren't taken then there can be some advantages to starting the groundworks in winter. Concrete needs time to gain full-strength, so the worst thing to do is to lay a foundation and then start throwing bricks up on it as quickly as possible. Wet weather and shorter working days can mean a slower build, giving the concrete and mortar more time to gain strength - but an absolute requirement is to protect the work from frost and rain. If the builder cannot be trusted to do that then don't build in the winter.

70sthrowback

we had an extension built over the winter months last year, it was only too cold to work for a few odd days here and there. The winter was relatively mild apart from some time in January, but the guys didn't come to site then and I was happy with any delays due to the weather.

At the end of the day its down to how much you trust / know your builder. Ours was excellent and so I was happy to trust his judgement around the cold and being safe / ok to work. He had a key to the house so could come in to make a hot drink and warm up whenever he wanted.