JOIST HANGERS'...Screws or Nails?

[lovelyjob]

Hi all. I am nothing more than a novice. Recently ripped out my Victorian wooden floor. The air vent was blocked and wall plates and joist ends all rotten. Now, after much humming and thinking I have fitted wall plates, 4" x 2" treated timber ready to take joist hangers. I could have used the previous method where the joists rested on a wooden sleeper which rested on the sleeper walls, see photo for sleeper wallsView media item 67904 ...but decided to use timber to timber joist hangers instead as this gets the timber off the damp floor. The new wall plates have been bolted to the wall and are level and I have bought timber to timber hangers in photo. View media item 67905 The joists are 4" x 2" treated also, set at 400mm centres, ready to take flooring T&G Chipboard.

Bearing in mind the floor will now be better ventilated but probably slightly damp as it is above bare earth...would it be better to fix hangers with screws...I have zinc yellow passivated 8's x 40mm...or use square twist nails.
The wall plate spans a wall 3.5m wide and joist span end to end is 3.6m with a sleeper wall in centre for support at 1.8m.

Will my method work...Or have I not used the best method for the floor at all?

The floor will be 18mm T&G Flooring chipboard, then underlay for laminate flooring. Would it still be an idea to add between joist insulation?

I look forward to your advice people.

 

[chickenlips]

For fixings, square twist nails always. screws sheer easily and should never be used.

You will need 150mm air gap underneath the floor and insulate between the joists with foil backed insulation (celotex or kingspan) is commonly used wich can be friction fitted.

 

[gregers]

what was wrong with the way the floor was installed originally?

maybe you are over complicating this,
bed down wall plates,run joists on top of plate making sure joist ends are wrapped in dpc and not touching any out side walls etc.

 

[b21playa]

What's the span of the joists? Is 4x2 sufficient?

 

[lovelyjob]

Thanks for the replies guys. In answer to some of your queries.

what was wrong with the way the floor was installed originally?

maybe you are over complicating this,
bed down wall plates,run joists on top of plate making sure joist ends are wrapped in dpc and not touching any out side walls etc.

I did consider repeating the same method. But as some of the sleeper walls needed some repair and I'm not experienced with mortar at all...I chose to fit wall plates. My thinking was that the timber would be nowhere near the ground and I wouldn't be messing with mortar trying to level the plates. It is true that I was slightly intimidated by this. I have looked again I feel I could have done it...but I chose the wall plate route. To give you an idea, fitting 2 of these, nice and level and very well fixed took me and my brother about 6hrs! Hopefully, fitting the joist hangers should be relatively easy now as I am now working single handed from now. It is true that I do have to fit a plate on the central sleeper wall using the original method.
I have asked in another post the method for this...I guessed Mortar bed, DPM, second mortar bed, then timber plate...is that correct?

Apologies for the separate replies but I cant figure out how to multi quote in the same reply as the quote boxes disappear.

 

[lovelyjob]

What's the span of the joists? Is 4x2 sufficient?

I hope 4 x 2 is ok. The span wall to wall is 3.5m with a central sleeper wall to help with the load at apprx 1.8m. The original Joists were 110mm x 47mm, so a tad deeper than 4 x 2.
The joists I have bought are treated Dry graded C24 M. Do I know what that means...not yet! But I will look it up.

I have another decision to make. Originally there were 8 joists. Which meant the centres were around 365mm (cant remember exactly). With 7 joists the centres will be 415mm...can I get away with this?

 

[b21playa]

http://www.home-extension.co.uk/tech2.html

According to that, 4x2 will work.

Just never used 4x2 for joists, always been minimum 7x2.

I was once told a simple formula: span of joist in ft divided by 2, then add 2.

So 6ft span (from wall to midspan)

(6/2)+2 = 5" @ 400mm centres.

 

[gregers]

I have asked in another post the method for this...I guessed Mortar bed, DPM, second mortar bed, then timber plate...is that correct?

in my post above is the method i use.never had any problems with it.
if your really clever,you could install all the joists,then using a couple of car jacks and some timber gently lift it all up,run mortar bed install wall plate.then lower the floor onto the plate that way it will settle at its own level.

 

[lovelyjob]

Thanks for the replies guys. All very helpful. Gregers...I have had another look at the sleeper walls and actually they are not as bad as I first thought..so I may go back to the original method using plates on these walls with DPM incorporated...even though I have already fitted timber wall plates to two walls! I don't know why, but my instincts suggest that joist hangers should be fine, but they will be relying on the bolt fixings in the walls. If they rust or degrade, the wall plate will come loose. I already have unbolted one plate as I forgot to fit a DPM on the timber against the brick wall. I never feel comfortable loosening and re-tightening bolts that have been wall plugged and was thinking of adding some through bolts for extra security...which is another pain in the ass job.
Using the original ground sleeper walls avoids all this uncertainty as the weights all down onto the ground. Maybe I was trying to re-invent the wheel somewhat.