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DIY/ Building question...

Fraser Jarvis

Well-Known Member
OK, I know it's probably not the right place for a question like this but here goes anyway.

I'm in the early stages of constructing my new office / studio, problem is with laying the floor joists i had to cut some wood from the bottom to allow for the uneven concrete underneath, now i have a very springy set of joists slightly raised from the original floor, someone suggested i pack out the gap with plastic window packers? I'm not sure that would work, i thought of using tiles but over time wont these crumble?
So if there are any building types out there I'm open to suggestions, thanks...



Among the pigeons
You could try running in levelling compound but you should have used it first.
Otherwise wide wood wedge packing, soaked in preservative, would be better than plastic.


New Member
what size are the joists and how long is the span? Did you use the correct size lumber for that span? I would double check the span tables.


Senile Member. Scandinavian Ambassadour of CaSLM
If the gap isn't too big (less than half an inch) I would just use some roofing felt to ensure support every couple of feet. If the gap is to big, I would go for tiles. No real reason why they should crumble.


put plastic down first to stop damp then the best to use is slate wedge them in and they won't crumble


Senior Member
G'day Fraser,

Second go at replying, (lost the last one cause my internet connection dropped off)

You really need to anchor down the Joists if they are spanning a large distance, You don't mention how long the span is, nor the size or spacing of the joists.
I would use some of that builders glue (in big tubes, brand names on this side of the world are "No More Nails" etc. Make sure it will bond Concrete to wood. If you are getting movement in the gap, I'd dyna bolt thickish brackets to the conc floor and screw also to the joists I hope there is no dampness in the existing floor and you have used dry joist which are suitable for the job in hand. If possible provide some ventilation to the underfloor especially if its damp...

Ask plenty of questions at your local Builders supply place, from someone (several of em) who looks like they would know.
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