Block and beam floor - height not correct with existing

[amuseboy]

New to the forum - so I hope I have posted in the correct section.

I currently have a double storey extension being built - previous builder did not complete the job, £12000 lost on unfinished work and now I have new builder completing the job.

Problem I have is that the block and beam floor is 90mm lower than the existing internal floor -on my specs, it says that I need to at a DPM, 75mm insulation and 75mm reinforced screed. Now that adds up to 150mm.

What are my options in getting the floor insulated and screeded to building regs? I really don't want the floor in the extension to be higher than the existing floor.

Oh and I can't lower it as the structure is already up and awaiting a roof.

Thanks for your help in advance.

 

[RedHerring2]

I can't give you a definite answer, but having investigated block & beam floors recently for my own project, I think I may have seen the option of insulation and a floating wooden floor.
Perhaps it's worth you investigating that option. Although I think it'll still leave your new ffl about 10mm above the existing ffl.

I'm sure the more experienced and skilled people on this forum can give you a more definitive answer.

 

[amuseboy]

Thanks for your help.

I am hoping there is a more efficient insulation that I could use so that I don't have to put in 75mm or the floating floor sounds like a plan.

 

[RedHerring2]

To give the experienced people an option on specifying a more efficient insulation, you'll need to specify what you intended to use.

 

[amuseboy]

Here are the specs:

Suspended concrete floor – ground floor
• Floor level to match existing.
• 65mm screed including mesh reinforcement.
• 1200g D.P.M. Laid under insulation minimum lap 150
mm.
• 90mm Kingspan TF70 insulation
• 20mm Kingspan TF70 at perimeter walls equal to
insulation thickness + screed depth.
• 1200g D.P.M. Laid under insulation minimum lap 150
mm.

 

[Static]

Hmm.. why is the screed reinforced? is it a composite floor or a particularly large area?

Ok.. one option if not a little more expensive may be to look into jetfloor or heatsave..

What spacing are the beams? and spans?

 

[amuseboy]

Stressline 125 x 150) pre-stressed ‘I’ concrete floor
beams at 530mm centres.

Infilled with Grade blocks with a maximum density of
1900 kg/m3 block size 440 x 215 x 100mm. Block to be
capable of supporting a 3.5kN transverse load over a
400mm clear span.

The extension is 4m x 8m wide.

 

[Static]

Stressline do a thermal composite option to their flooring.. it basically replaces the blocks with blocks of polystyrene.. but you then need a higher spec screed with reinforcement.. this way you can get away with a 75mm screed over your floor and only be 15mm shy of the mark..

 

[amuseboy]

What are the downsides of using 50mm insulation and 50mm screed?

 

[amuseboy]

I should have added - I need to find a solution that doesn't require me to replace the blocks and isn't too costly.

Having lost £12000 I am struggling to finish the extension.

Thanks so far!

 

[amuseboy]

Looks as though I may have found a solution - I can install 70mm celotec floor insulation and then use battens to install a plywood floor. I'll probably use 20mm ply to match the existing floor height.

Any one got any thoughts?