fresh concrete and wooden floor

[Neber]

I have just reduced the size of my fireplace foundation ready for a new smaller fireplace so now need to extend the subfloor over the gap ready for a solid wood floor on top. I need to bed this short section of joist into a gap in a couple of breeze blocks ready to support the subfloor

Question is: Can I use cement or might the moisture cause a problem (as I plan to lay the solid wood in 4 days) ? anything else I can use?

Also while I'm on the topic the fireplace installers said they would use a dry concrete mix to hold the base of the fireplace. This will be laid just after the floor and will overhang the floor slightly, should I stop them using concrete for that too?

Thanks

 

[JohnD]

If you are anxious about the wet concrete affecting the timber (it will not be wet long enough to make it rot; but it WILL make it expand or warp, and be loose when it dries and shrinks) you can wrap the timber in polythene or put down a sheet of it.

For a small job even cling film will do as the concrete will be dry in a week or so.

 

[Neber]

Thanks for the tip hadn't thought about the joist swelling and becoming loose. However I was worried more about the solid wood floor than the joist though any tips on an adhesive/filler.

 

[WoodYouLike]

Neber: rule of thumb: every inch (2.5 cm) of concrete takes 30 days to dry out sufficiently to safely install a wooden floor on. I do realise it's a small area but even so.

 

[Neber]

How about a grip fill adhesive like no more nails or a tub of epoxy?