Bouncing joist

[Harris.W.Morrison]

Hi all,

Having moved into a new, to us, detached house we have discovered that some of the floor in the kitchen is quite "bouncy"! Now, we're getting a new kitchen fitted and this seems the perfect time to fix 'the problem'. The builder talked about 'soldiers' to lift the joists and stop the bounce but having looked below the floor panels, it's bitumen and probably useless for his idea! So, anyone else come across this and if so, what was the fix? One worry is that the gas pipe is in a similar area to the bouncy part and a worry is that they've cut into the joist to make it fit!!

Thanks for any replies.

Harris

[Phil L]

One or more of the joist ends have probably rotted away - to do it properly, you need to remove the floorboards, cut away the rotten ends and replace with new joists attached to your existing ones, these will need wrapping in DPC before being inserted in the wall, and some dwarf walls underneath built underneathwhere you join the two joists together would also give added support.

Your remarks about panels and bitumen are baffling

[Harris.W.Morrison]

Phil,

I know at one end, the joist looks fine as I had an electrician friend in fitting a new socket and we had the board/sheet up at that point. The fault must be nearer the inner wall which separates the kitchen from the dining room which I can't access just yet but will be able to soon. Thanks for the advice but building a dwarf wall on top of a bitumen base wouldn't work though the thought behind it is good. The house construction here is what appears a dwarf wall around the edge which the joist sit on and the space inbetween, i.e. directly under the floor joists is bitumen (That black stuff). Guess it's for damp or something but I'm told it'd common enough up here. The panels are the sheets of chipboard they use to floor the rooms in instead of proper floorboards.

Harry

[Roger Mills]

I don't understand why you can't build a dwarf wall on bitumen. If the bitumen was a foot thick, I'd agree - 'cos it would get squeezed out by the load it was trying to support. But, in reality, it's probably only a couple of mm thick - painted on top of a concrete base. If this is so, building on it is *not* a problem.

[meow2222]

First things first. The reason why original boards were replaced with chip is more or less always rot, so you may have a rot problem. Need to check underfloor venting is sufficient and unblocked.

Now, bounce can be caused by 1 or more broken rotted joists, or simply by the normal result of cut price building practices not uncommon back in the days of suspended timber floors. IOW bounce does not always need any remdy.

If a joist is broken at one end, the rotted section can be cut away and new wood bolted on, and fixed with a joist hanger. Replacing the whole joist is more work, and not usually needed.

If a joist is deeply notched or otherwise damaged, and this is the bouncy area, noggins to neighbouring joists will resolve it. Noggins must fit well to work, no gaps.

If the whole structure is bouncy and this will be a problem with a washing machine, a dwarf wall is a fine plan. Sitting it on bitumen is not a problem in itself. But the bitumen might be a layer on felt or sand on soft soil, in wich case a firm base is wanted.

The dwarf wall must be riddled with holes to keep ventilation levels good, so gaps between most of the bricks / blocks are wanted.

NT