Raised Timber Flooring on Concrete Slab

[Bronson]

Just searched this forum extensively but I couldn't find anything to help me specifically.

I would like to build a raised timber level in my lounge room and bedroom. About a 200mm step up. I got the idea from some display homes in the area.

I'd just like to know the best way to go about doing this. Fixing it to the slab? How to go about getting the height i need? Should I do it now or wait til the plaster is done? (my house is currently being built, the frame has just been completed), Allowing for movement? etc, etc...

Any advice is appreciated

[OBBob]

I guess you could build it like you would build a new floor? If you used 90mm bearers (dynabolt to the slab?) with 90mm joists on top plus 20mm floor boards you'd be around your 200mm mark.

Maybe put the frame in before the plaster but then the floor boards after the plaster has been in a while.

I assume you don't have any doorways or windws that will be affected by raising teh floor 200mm??

[Bronson]

Thanks for the reply OBBob.

The windows are about a foot from the floor so thats not a problem. No doors to worry about.

Why do you say to put the floor in after the plaster has been in a while?

[OBBob]

I'm not expert on it but timber floors can be affected by the moisture in drying plaster, cause expansion and warpage etc. You'll notice that even when you buy new timber doors they often have warnings on them about not leaving them in freshly plastered rooms.

I guess the other option is to do the floor first and seal it properly, then plaster? I think the key is just not to do those two jobs too close together. You'll find plenty of horro stories on here about how timber floors can go wrong.

By the way I like the idea ... have seen split level floors in a few places and think they can look really great.

[Bronson]

Thanks for the info - makes a lot of sense!!

[DJ’s Timber]

I would also think about putting some form of sound deadening under the floorboards as well.

I would imagine that it would have an echoing effect, being a sealed box on top of concrete

[Sturdee]

I have done it in part of the downstairs area. I used hardwood beams of 200 * 50 mm with spacing blocks in between and covered it yellow tongue boards as the area was to be carpeted.

Using hardwood beams rather than bearers and joists is much easier and they don't need to be bolted to the concrete as the weight is sufficient to stop it moving. But maybe a bead of construction adhesive could be used.


Peter.

[Bronson]

Sturdee. Did you put the spacing blocks level with the top of the beam or at the bottom?

[Sturdee]

For the spacer blocks I used short pieces of the same type of beam and slightly ofset against each other ( similar to ofsetting of wall noggings for easy nailing) so that the beams can't twist out of shape.

Got the idea from the way the builders used oregan beams for the upstairs floor.


Peter.

[Bronson]

Thanks for that Peter.

Is there any regulations about how high I can make this platform? Do you think 300mm is too high?

[OBBob]

I think 300 is fine as long as the stairs conform to the BCA. I think the regulation is above 600mm to require any railing etc.