what can I do about creaky, bouncy floorboards

I have recently purchased a new house with a rear extension that had been completely re-stumped. The previous owners laid down floorboards to match the many, many-year-old floorboards in the rest of the house. Unfortunately, I'm now finding that these new boards are creaking a lot, and there seems to be a lot of putty, i think, being dislodged from between some boards. There also seems to be a lot of movement with some of the boards, in that they don't feel so solid beneath feet. Anyone suggest what might be the problem?

I'm no expert, but it sounds to me as some of the timbers used weren't properly dried and are warping as they dry. Could be the floor joists, could be the boards. If you only want to stop them creaking, then you need to get under the floor and pack the gaps between the joists and the floorboards. You could use fine timber wedges, nails, washers or all manner of materials to achieve this. It's easiest done with two people, one walking on the floor to identify the creaking boards, while the other is under the floor packing them as you find them.
From what I know, you don't want to try and glue them down, you need to pack the gaps.

I'm sure someone more knowledgeable than me will be along soon to help you further.

Yeah ... it's often not recommended to fill gaps between floorboards because it looks great to start with but when they expand and contract during the year the putty starts to fall out.

If they were recycled boards you may find they didn't all have tongues, which would cause them to fell a little more bouncy under foot.

I think you will need to do as Dean suggested and probably have a good investigation under the house.

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Originally Posted by hasian

I have recently purchased a new house with a rear extension that had been completely re-stumped. The previous owners laid down floorboards to match the many, many-year-old floorboards in the rest of the house. Unfortunately, I'm now finding that these new boards are creaking a lot, and there seems to be a lot of putty, i think, being dislodged from between some boards. There also seems to be a lot of movement with some of the boards, in that they don't feel so solid beneath feet. Anyone suggest what might be the problem?

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Could be any number of things and definitely calls for a trip under the house. :(

Joists too far apart, allowing deflection.
Gaps between the boards and the joists as Tas Dean says.
Squeaks can be from boards simply rubbing together because improperly fastened (and is very easy to fix), but deflection needs a good investigation. :)

Thanks all for the suggestions.
Will get under the house and have a look very soon.
Fingers crossed