Poured in Place Chimney Caps

snowy393

Hello there,

I have just poured my chimney caps this evening. The carpenter put up the timber shuttering for me. The problem is I forget to put anything on the timber shuttering to prevent to concrete sticking to the timber. The caps are quite big and thick, the timber was quite smooth. I am wondering is there anything I can do now to rectify the situation or should I just take down the caps before they get too hard and start again.

Will it help if I leave the shuttering up for a longer time than normal??

Thanks for your help.

Carlow52

I would leave the shuttering on for as long as possible: 28 days to cure full strength.

As long as u dont gunter it when taking the shuttering off it will work out okay.

In most cases the underside of the shuttering is left on for a good while anyway.

If you wet them while the concrete is curing it will help and

reilig

I'd be the total opposite and tell you to make sure that you take off the shuttering in 7 days before the concrete cures and really sticks to the boards.

I shuttered my chimney caps, didn't put anything on the timber to stop the concrete sticking to them and took them off after about 5 days. They turned out perfect.

Boards that are left around concrete until it cures can often bring a small corner or edge at removal time.

snowy393

Thanks for your advice so far.

I do have a certain time restriction anyway for slating and removing of hired scaffloding anyway. 7 days will be fine though. Should I keep putting water on the concrete as it is curing over the next few days. The mix I used was a strong mix of grey sand (not gravel) , cement and lime + rebars. Hopefully the caps will come out allright now.

Quazzie

snowy393 wrote: »

TShould I keep putting water on the concrete as it is curing over the next few days.

I think you might be forgetting you are living in Ireland. There'll be more than likely be plenty of rain on it over the next week

mickdw

I would recommend also a flexible heat resistant sealant between concrete cap & chimney flue. Best way to do this is to place a flexible strip around flue when pouring then remove this and fill with the heat resistant sealant. This will stop cracking around the chimney.

snowy393

Thanks all,

Took down the shuttering today. Very gentle with it and applied alot of water today and yesterday to help seperate the timber from the concrete.
The caps worked out perfect. No problem at all seperating/removing the shuttering. The finish was very smooth and looks well.

Poor Uncle Tom

before pouring the caps what damp proofing/closer did you use ? just curious.

snowy393

I just put some radon barrier between where the sand ends and the cement begins. The poured caps are about 9 inches thick in total.

Poor Uncle Tom

snowy393 wrote: »

I just put some radon barrier between where the sand ends and the cement begins. The poured caps are about 9 inches thick in total.

:eek:
slate is best or lead but not into the pot area as it can get very hot there.