I'm finishing a self build with suspended timber floor. Looking at oak floor and whether to go for solid or engineered wood. Am looking to glue T&G boards down to 18mm OSB which is fixed on top of ijoists insulated with 300mm of glasswool. The OSB is level and flat.

Welcome advice on what to go for and how much I'll expect to pay for a decent product. Thanks in advance.

I would go floating floor using engineered planks

<blockquote><cite>Posted By: owlman</cite>Either solid or engineered both are fine. Solid obviously allows for future sanding and refinishing to a greater degree than engineered, but some engineered has a decent wear layer. Good quality engineered may work out dearer than solid and not available in as many size variants. For wide boards go engineered.
Raw boards or pre finished is another question. I'd go for a pre sanded board and final finish yourself afterwards.
As for fixing to a suspended floor, personally I'd use a Porta-Nailer and secret nail, it allows for movement more so than glueing although many adhesives profess flexibility. I also like the satisfied feeling that laying a whole nailed floor gives.</blockquote>

Thanks Owlman, why pre sanded? I've been offered at a good price high quality engineered 14 ply birch with 6mm oak top. The ones finished with either oil or lacquer are a little bit more expensive than the unfinished, though the cost of finishing myself is higher.

Just to add a random influence ....

We went with stranded bamboo instead of engineered timber. It's much harder than wood and doesn't move much. We used a flexible Sika adhesive to stick it to a Caberfloor substrate and it's been fine so far (5 years). Visitors tell us it looks good and we think so to, of course.

We went for pre-oiled (engineeered) and have recoated with Osmo since.

One advantage of pre-finished is that it does give you some protection from stains/marking while you're fitting (and also means you don't have to worry about difficult to reach areas (which don't get any wear and won't need reciting in future)

<blockquote><cite>Posted By: Simon Still</cite>We went for pre-oiled (engineeered) and have recoated with Osmo since.

Did the Osmo match well without discolouration?

I too went for pre-oiled engineered floating laid before the skirting - it gave some protection whilst the builders, electricians and plumbers and were around - it took a coat of Osmo without issue (so far).

Each plank interlocked with the neighbouring one length wise using a "S" shaped profile - In addition the end's also interlocked with some plastic inserts - in effect no gaps can form within the floor body - all movement will take place under the skirting and architraves. Because of the nature of the interlocks you need to plan very carefully for any planks that need to slide under any obstructions.

Too late now Will, but did you put the usual cork cushions as spacers into the expansion gap?

Cheers Owlman, but it came as a system and it was quite specific not to have anything in the expansion gap - you put solid spacers in during fitting to set the correct expansion gap, but remove them when done.

Posted By: owlmanEither solid or engineered both are fine. Solid obviously allows for future sanding and refinishing to a greater degree than engineered, but some engineered has a decent wear layer.

Indeed. Some/many have a wear layer so thick that you can sand them as much as solid. eg enough that the T&G appears/fails before the wear layer runs out.

So have opted for untreated engineered oak and glueing it down. Looking for a bonding agent which is zero or low VOC. Any recommendations? I'm presuming that glue will form an impermeable seal above the earthwool insulation below?