Joist Hangers On Blocks

[raybush]

I have a two storey side extension on my house which is constructed in blockwork.
My problem is that the first floor flooring joists are laid in joist hangers which then rest directly onto blockwork, the problem is that over time where there has been a small amount of movement in the joists it has worn the block/s which in turn is causing problems with the floor which has started to creak and will in time cause problems where the shower y is situated.
I was going to use an acrow-prop at either end of the garage(which is the ground floor area) with a small RSJ and prop that up to see if it will hold the floor firmer, only problem with that is I have quite a number of pipes right near the edge of the room and cannot get a RSJ where it would need to go without moving pipes and causing more work.
Not to sure what easy options I have to resolve my problem.HHHEEEELLLLPPP.

[malagabob]

Can you take and post some photos?

[Togo]

Ray are the joist hangers the jiffy hangers,that bolt directly to the block work,
or the stiff hangers, that are lipped into the blockwork between courses? If they are the latter can you add bolts (if none are fitted). If they are the former is it possible to remove them and fit bolted stiff hangers. This would mean chasing out the mortar and again rebolting. Looks like a one at a time job whatever. Also, is there any possibility that it is the boards themselves that are creaking?

[Togo]

Just had a read through your op Ray. When I did I have to assume that you have the jiffy hangers that are bolted straight onto blockwork. Now if that is so and there is movement it means that you cannot use the original fixing positions because of damage to the blocks. So you may need extended joist hangers that will enable you to fix into undamaged blocks. Youill need to make sure that you get the right sized hangers to suit your joists. Not a job for the impatient, or that can be hurried, I think. I have posted a lonk that shows the sort of hanger. Others are available.

https://www.uktradefix.co.uk/building/joist-hangers/100mm-extended-leg-jiffy-hanger.html

[raybush]

Thanks for the replies.
The hangers that are there are just laid between the courses of blockwork ,I believe that the bit that sits on top of the block is about 2" wide .The extension is over 20 years old and the size/design may have changed now to give more width to sit on top of the block.

[The Builder]

Sounds like you have "build-in" hangers. They should be fitted during construction. Laid on the block course, then the next course is laid in the usual way.

If done properly, they should never move. What sometimes happens is that the blocklayer doesn't want to do this, usually because they can't be bothered. They simply cut a slot and drive them in afterwards. This is totally wrong, and they will loosen in time. Maybe that's what happened here.

I can think of two ways of dealing with this. You could use a resin injection system to squirt resin adhesive into the gaps. This is used for anchoring steel columns to the ground, so it's obviously good and strong.

Rather than a steel beam, I would just bolt a piece of 50x100mm to the wall right under the joists. Perfectly strong enough..... or maybe your pipework is in the way for this?

[Togo]

You have a definitive answer now Ray. Builder give advise on the "Bank" that is priceless. I would not have known the best way to remedy stiff, or as Builder calls them, build in joist hangers being loose but, I do now. Clever Builder, false wall plate. :))
Hope you are well Builder and keeping out of the bad weather. My Brother was on a roof in Leek last week and is still recovering. Sorry to pinch a bit of your thread Ray.

[raybush]

Again thanks for the replies.
I think you may be right when you suggest that the joist hangers were put in afterwards. I had thought of propping-up the joist hangers ,but I know the blocks used were the White Durox type and didn't think I would be able to get a good strong fixing into this type of block to hold the timber up under the joist hangers,if it were brickwork that would be a different storey as bricks can normally take some type of anchor bolt without fracturing when tightened, or am I wrong? .

[The Builder]

Togo, many thanks for your very kind comments. :o)
Yes, I'm well out of the winter weather. Right now I'm rolling out the underfloor heating pipework. I don't usually go outside until Spring arrives ;o)

Anyway, Ray. Durox blocks are my favourite. But, if the hangers were driven in afterwards, then there's no chance of them being held firm in Durox. Installed properly though, they would never move.

All the usual rawlplugs/frame anchors/fixings will hold just as well in lightweight blockwork. You just have to be a little more careful in drilling exactly the right size hole.

Use any of the many brands. "Fischer sleeve anchors" are ideal. Rather than a big fat rawlplug, they have an expanding steel sleeve that opens up as you tighten them. One of those every 600mm should do it.

The reason why the hole size is important, is that: too big, and the sleeve won't grip. Too small, and you'll mess up the sleeve by driving it in.

[raybush]

Thanks for your reply Mr Builder.
I'll have a look at the Fischer Sleeve Anchors and familiarise myself with them.
What I may have to do is where there has been slight movement in the joist hangers is to jack up the ones that have dropped a few mils and then as you say bolt lengths of 4"x2" under the joist hangers along the block wall.
I wasn't aware that you could get a strong fixing in blockwork.
Again thanks for your help and for opening my eyes as to a remedy for this situation.
Regards Ray

[raybush]

Hi Builder

Thanks for your time ,one more question - what size of fixing would you use ?for 4"x2" timbers that I need to bolt under the joists.
Thanks