Noise

Now that the two big rooms have been plastered they are serviceable rooms (at least the one that isn't piled high with "stuff" is). We have temporarily moved into the "new sitting room" in order to clear the "old sitting room", which is the last remaining room in need of a ceiling and a visit from the plasterer.

This room is empty so that we can press on with the preparatory work. One of the problems we have to solve is the creaking floor when Victoria walks across her room above. It is a new floor, constructed by the builders with nailed down tongue-and-groove floorboards. However, Jan and I have inspected the underside of the floor and come to the conclusion that the noise problem is not the floorboards themselves, but the shoddily constructed structure that supports them.

A wall plate has been bolted to the wall either side, and joists suspended between them using galvanised joist hangers. In an ideal world (i.e. if we had constructed this), a slight notch would be taken out of the underside of the joist at each end, to accommodate the bottom of the hanger and allow easy flush fitting of the plasterboard ceiling sheets. This is far from what has actually been done here. You can see from the picture below, that some of the joists do not even sit on the bottom of the hanger. This is one of the worst, with a gap of nearly 1/4 inch :

The joist is effectively hanging from the nails that enter the hanger from the sides.

Problem number 2 is the noggins. These are the blocks of timber that sit between the joists at points in their length, to stop them from twisting. A number of them have been cut too short, so there is a gap on one side :

As you walk across the floor above, the nails through the joist into the noggins are able to move a little, hence creak.

The final problem we identified is with the last joist, adjacent to the end wall. Again, this is suspended between it's two ends with joist hangers, but is not anchored into the end wall with anything.

We set about resolving these problems last week. Firstly, the last joist was attached to the end wall with 4 anchor bolts (2 shown in the picture) :

I used "sleeve anchors" :

The advantage of these is that the same size hole is needed in the item to be attached, as the wall it is to be attached too. The whole anchor was able to slide through the joist and into the wall,with a washer behind the nut when everything is tightened up. The wedge at the end of the sleeve forces the end to expand and anchor into the wall.

To make everything nice and firm, I eased some spacer blocks of wood and ply up into the gap between the two, each custom planed to fit the gap :

With the end joist now firmly anchored I cut out the undersized noggins and replaced them with new, cut on the chop-saw. In the end I replaced, or in some instances, doubled up, 8 out of 16 of the noggins. To make sure they were a good tight fit, I eased the joists slightly apart with a sash cramp :


The floor is much quieter now, though still not perfect. We have still to address the problem of the badly fitting joist hangers though. I suspect this going to have to be a case of wedging in ply spacers, and then cutting the plasterboard to fit around them.

While on the subject of noise, I have to report that we are hugely disappointed in the amount of noise transmitted through the floor from the new room to the bedroom upstairs. As regular readers will know we went to great effort, and expense, to install acoustic slab insulation between the joists before putting up the ceilings. e expected this to damp out all noise coming from below, but sadly, it simply has not worked. You can hear the TV as plane as if you were in the room. Jan thinks the cause may be the light-weight celcon blocks used to construct the inner wall of the extension. Good thermal performance, maybe, but sound transmission may be their Achilles heal.

Unfortunately, there is not much we can do about this now.