I'm building a house with a B&B first floor near Huntingdon.  Our Architect wasn't keen initially because it complicates the design. We insisted thats what we wanted because our current house has a B&B 1st floor and we love it. There isn't a single squeaky floorboard in the house and the kids can jump about upstairs without the whole house shaking. If you are thinking of having a wet room style bathroom or ensuite it's ideal - no risk of floor tiles or grout cracking.  

It's possible your Architect isn't familure with designing for a B&B 1st floor. In which case he may change his mind if you mention the possibility of employing a Structural Engineer to do the loading calculations However this is where some of the extra cost is.  We needed an SE anyway because our design has other complications like arched windows, large spans and a complex roof. Our SE's bill was £5000 but not all of that is down to the B&B floor! Don't rely on the layout drawings from the beam and block company - you do need the layout looked at more carefully and the sums will need to be sent to BC for approval. Our SE had the Architect change the way the B&B floor was supported - He added a few brick pillars and made other  changes to the design - like our chimney.

I can't really compare the cost easily but the materials cost of the beams and blocks don't seem that bad. Our 1st floor area is roughly 1600 sq feet on three levels. The quote for the concrete beams was about £1300 and the blocks about £600-700 (if I've done my sums right). Plus you need screed and insulation. We also used B&B for the ground floor and it was laid in about two days. We haven't got as far as building the first floor yet. Try Rackham floors for a quote.

If your house is a funny shape it might be worth using a mixture of construction. Use B&B for the rectangular areas and wood where there are cut outs. For example the gallery landing on our design will be wood because otherwise we would need the concrete beams to "overhang".  

It's worth pointing out that UFH can work well with a wooden first floor. There are several different systems but they all have some method of distributing the heat - typically they use special metal plates betweenthe pipes and the wood.  

If your Architect or Building Control start talking about the need to do expensive sound tests (to ensure compliance with Part E- Sound of the Building Regs).... Tell them it's not necessary. The reason this issue might come up is because (to my surprise) there isn't a so-called "Robust Standard" design for a Beam & Block Floor with UFH listed in the Building Regs. The nearest approved design has the screed directly on the blocks without any insulation between.  To get round the need to test you can can get a certificate of compliance from the B&B floor companies for a floor design _without screed_ that meets the specification. It took me weeks of delay to sort this out. I can give you more details if this issue comes up.

To keep the overall floor thickness within reason the make up of our floor will be as follows...

14-18mm Floor covering (carpet, tiles wood etc)
65mm reinforced screed
35mm insulation  with slots for the UFH pipes
150mm Beams and 100mm blocks
38mm battens and 38mm sound insulation
12.5mm plasterboard and plaster skim

If you want to fit recessed downlights in the rooms below (eg kitchen) you will need to use the type that meets Parts B (Fire) and E (sound) WITHOUT the need to add a fire/sound hood. This is because the void space is only about 100mm deep. There are at least three sources of downlights that meet this spec but you probably won't find them in your local DIY store. Let me know if you can't find them.

Colin  (colin.watters@pandoraBOX.be - remove BOX to get real email address)

Have been in my house just over a year now and I had what is called Hollow core floors at first floor. They come along and measure when you are out of the ground at dpc....by the time you have the first lift ready they come along with them on a lorry and lift them all into place in about three hours...job done and you have a solid base to work straight off. Will try and dig out a link, they were not that expensive either, they are insulated too and absolutel superb.

cw, your replies to questions are astonishing m8. well written, concise and helpful. imo you are a great credit to this place.

btk

No problems.

As Robbo mentioned hollow core slabs are an alternative to B&B.  I believe you need to specify any cut-outs or L shaped slabs when they are made.

Here in Belgium there is also a third option thats a bit hard to describe.. You buy concrete beams that are only about 1" thck. They come in various widths from say 6" to 3ft wide. They are laid flat side by side. The top surface has pyramid shape reinforcing rods on it (like stand-offs). When you have covered the whole area with beams you put mesh on the top and pour concrete. The result is a solid concrete floor. I saw them at a show in Brussels and the maker claimed that the 6" wide version was light enough to be laid by hand without a crane - although I wouldn't want to!