Sub floor Joist Setting Out

[padstar]

After ordering the timber a few months ago i have managed to get a week off work and want to get the sub floor down to release the UFH.

I plan to install perimeter timbers to all external walls fixed with M12 studs @ 600mm centers chem fixed into masonry.

I have dwarf supporting walls at each 2m span with timber wall plates bedded onto them.

Joists are to be spaced at 400mm centers, hung from hangers on the ledger boards and sat and nailed to the wall plates on supporting walls with 2 noggins for every 2m span.

Firstly is the above the correct methodology?

My questions are;

1) Is there a position to start from? Do you start at one side a move across or start from the center and work outwards?
2) Is 2 noggins per 2m span (1 mid span and 1 at supporting wall location) suficient?
3) The floor structure above will be 22mm chipboard grooved for the UFH pipework with a 6mm ply on top. Will this need noggins at each sheet joint?

 

[Bonni]

Well, nothing wrong with what you've outlined, it'll work. With the price of wood, it'll be cheaper to cut the perimeter wall and use joist hangers so you can do away with most of your timbers in blue.

Just glue all the chipboard together, no noggins required. Doesn't really matter where you start, just as long they're no more than 400 centres and they make any pipework easier. Use a chalk line and draw a 10cm grid on the plywood to screw it down every 10cm. It'll take a few thousand screws.

 

[noseall]

1) Is there a position to start from? Do you start at one side a move across or start from the center and work outwards?
2) Is 2 noggins per 2m span (1 mid span and 1 at supporting wall location) suficient?
3) The floor structure above will be 22mm chipboard grooved for the UFH pipework with a 6mm ply on top. Will this need noggins at each sheet joint?

Your start point will be access relevant i.e. start at a far wall and work back. The important thing when setting out (marking the joist centre positions) is to measure where your first floor board joint will land from off the start wall, position a mark there and then set all your markings say 400mm c/c either side of that first set point.

How are you going to install your insulation detail?

Have you factored in air bricks and cross ventilation?

Not sure you'll even need midspan bracing with those (wall span) centres.

 

[padstar]

Thanks Noseall,

There are airbricks installed in the blockwork and they will sit just below the joists. The mid span walls are open to allow ventilation so there should be good airflow under the floor.

I was planning on fitting small battens to either side of the joists to slide 100mm of insulation between them.

On the start point and following the logic of not building myself into an area i cant access would it be sensible to start in the bottom right corner working backwards as below

 

[Deleted member 292770]

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[padstar]

Screw down every 10cm? Thats 2000 screws?

Is there a preference in screws for the job. I obviously dont want this moving. Do you just screw or glue and screw?

 

[padstar]

I have seen a lot of people using the "expanding" PU adhesives. They look decent and will fill any small gaps. Again do you have any recommended products for the glue?

 

[padstar]

The UFH pipework is 12mm from Continel. They recommend 6mm ply over the top but was thinking of upgrading to 9mm. I need to speak to their technical department to see if this has any negative effects on the performance.

 

[padstar]

Sorry a few more questions regarding fixing teh ledger boards back to the wall (I already have the timber so will go down this route).

Using M12 bolts am i correct in thinking i need a 14mm hole through the timber and a 16mm hole into the blockwork?

How far into the 100mm block do i go for the chem fixing?

 

[noseall]

Sorry a few more questions regarding fixing teh ledger boards back to the wall (I already have the timber so will go down this route).

Using M12 bolts am i correct in thinking i need a 14mm hole through the timber and a 16mm hole into the blockwork?

How far into the 100mm block do i go for the chem fixing?

80mm in.
Why are you chem fixing? Just use a standard rawl bolt.

 

[padstar]

Perfect thanks. Was chem fixing as some of the fixings are close to the edge (near the rear door) didnt want to blow the blockwork with a rawl bolt.

 

[catlad]

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