Floor sagging - too much furniture or simply old house?

[dave163]

When I bought my late Victorian terraced house the building inspection pointed out the floor in one of the bedrooms (approx 14 foot square) was sagging a bit but didn't advise there was any problem. I recently measured it (taut string from corner to diagonally opposite corner) as being approximately 20mm dip in the middle. The ceiling in the room below isn't visibly sagging. The floor in the sagging room is made up of floorboards at 90 degrees to joists which I'd estimate to be 8 inch by 2 inch and probably between 18 inches and 2 foot apart though it's a while since I last had the carpet up to measure and it's now all but impossible to check without taking everything out the room.

Having recently installed a very heavy piano (think perhaps 350 kg once player is sitting at it) that is along one wall sitting parallel to the floorboards (ie it's straddling perhaps 5 or 6 joists) followed by four Ikea-style 6 foot high bookcases (probably each one weighs 100kg with books) which are on opposite walls and running perpendicular to floorboards ie each will be supported by one, maximum two joists), I thought I should just check with the experts here whether I need to do anything to protect the floor. It's always been a bit bouncy, though is probably noticably so now that the kids are old enough to jump up and down on it.

If I did need to reinforce the floor would I be better off tackling it from above or below? It possibly is a tossup between the hassle of moving a piano and bookcases out the room and storing them while the floor's up versus removing the ceiling in the room below and then having to redecorate that room - so in all honesty if it sounds like the floor will cope I'd rather just live with it. Any suggestions?

 

[TheVictorian]

Personally, I'd be happy that it will be fine. These floors were over engineered by modern standards and if it has moved 2mm every ten years then that's not much to worry about.

However, you may want to check the joists to make sure that they haven't been eaten by woodworm in the past or that they haven't rotted where they contact the external wall. I only say this as there shouldn't really be any springyness in a floor made of 8x2 joists in my experience.

 

[tony1851]

If its a 14 ft span and the joists are 8x2 at 18" centres, it would be surprising if there wasn't some bounce in them; they would be undersized for that span by modern standards.

Having said that, timber floors very rarely collapse, even under high loads, but they do bend and bounce. With those loads, I would, however, take the trouble to check that the bearings in the walls are adequate.

 

[lockjohn]

this may be easier from below but you would need to jack up floor and bolt extra timbers to each side of existing joists and if possible put in extra joist as they are wide spacing on existing joists

 

[gregers]

or maybe install solid noggins across the whole floor.