Solid floor or Block and Beam which is best

Hi,

I've had a couple of quotes fro an extension and both came in very similar. The only difference being one builder was going to use a block and beam floor and the other a solid concrete floor.

The floor to the rest of the property is block and beam. Are they any advantages/disadvantages to having a block and beam floor. I'm worried that the floor will be colder due to the airflow under the floor or will this not be a problem if it is insulated properly.

If you go for the solid floor, then the venting arrangement to the existing pot and beam floor will have to be maintained.

No floor type will be colder than the other: the insulation will deal with that.

Both floors will be insulated to the same standard.

The only difference to you as the end user, will be that if you have a cabinet with china plates and ornaments, then it will rattle like hell as you bounce across the suspended floor.

Sorry to say Woody all suspended floors dont bounce. Back in the 70,s we used to span 4ft with 4x2 joists with 7/8" finished floor boards, No bounce

Modern way . Span 6ft with 4x2 with 3/4" chipboard-BOUNCY

Cure for modern - 5x2 & floorboards

Erm, Woody was talking about pot and beam floors bouncing

It may well be that there is a structural reason for your existing floors being supported off the perimeter walls (as in the beam and block system), rather than the ground. Or it maybe that it was just the original builder's preferred method of construction.

Do you know if the original foundations are overly deep or indeed piled? Either of these would indicate a need to have a floor of more than just plain concrete on the ground...

If you're lucky, you may get some information and reasoning behind the original construction from your local council (Building Control).

The house is built on a slope that has been tiered, there are retaining walls between myself and neighbours houses. One house 10ft higher than mine the other 10ft lower. Not sure if thats why we have beam and block. I hope I don't have to overly deep foundations for the exetension, the builder has quoted for 1m footings and when I dug a test trench I told him apart fromabout 2ins of top soil the rest looked like sand. He said all the houses around here are built on sand and 1m footing would probably be fine. Famous last words !!

Oh boy, that's definitely why you have beam and block floors in the original!
It's hard to say for definite without seeing the lay of the land and the relationship of the 10 foot drop to your extension, but it's more than likely you'll need a beam and block system again, or a cast-in-situ, reinforced concrete, suspended ground floor slab. (Enter Shytalkz ).

Again it's hard to be definite without more detail (and a crystal ball for the ground conditions), but if the extension is anywhere near to the '10 foot drop', you're going to be in for a 10 foot dig for any plain concrete strip foundations in that locality, so that the pressure exerted from the foundations doesn't load up and affect the retaining wall.
Also, if the ground has been (built up and) levelled off to form your garden you could be in for a deep dig just to get to original (undisturbed)ground levels. If the locality is all sand below the surface it can be very difficult to establish the original ground, as the house builder will have made your garden up with the sand he dug out from another area of the site.

If a 10 foot (or anything similar) dig looks likely, you'll not get it dug by hand (too dangerous), and if you can't get a JCB or similar in, prepare yourself for some extra foundation costs, maybe mini-piling. Soz!