Beam & Block flooring

[The Other Mike]

Anyone here done one themselves and got any tips on good suppliers and construction details?

It's for a single floor timber framed outbuilding (aiming for Passivhaus standards) footprint is around 5m x 4m

[Bob Minchin]

I looked at it about 10 years ago for a similar sized job (3m x 10m) and the killer was cost of transport for part loads of the beams. Manufactures like customers who can take a full wagon load. Maybe now BMs are starting to stock the beams and if you can base the design around off the shelf sizes or angle grind down to size.

[The Natural Philosopher]

yes. Bu t too long ago to be off any real use on suppliers etc

I am not sure you can span 4m without central supports.

The way the houses I saw being built last year were done was this.

block foundations to about 1 ft below finished floor, then DPC overlaid and the beams laid on that with some sort of cinderblock like spacers, and infilled with about 150mm of white EPS foam. Underfloor vents were fitted

A further 100mm or maybe 150mm EPS was laid on top of that, UFH pipe was pegged into that and the whole thing given about 150mm of concrete...with more insulation at the edges of that slab to prevent it cold bridging to a little more blockwork that formed the boundary of the floor slab itself.

Above that level this builder used timber framing with celotex infill, but block and cavity fill is also possible.

Really all ths stuff is produced to a BCO spec so any manufacturer will supply the gory details and its all stressed to a standard so its really just a matter of picking a supplier and doing it.

A crane or other lifting device is handy - the beams are not light, and a decent angle grinder capable of cutting them is also useful.

You will need at least one other fit person to help

[dennis]

You need to be careful if you want to cut them down as they are prestressed IIRC. That is why the beams are curved and flatten out when loaded.

[Andrew Gabriel]

As someone who often threads services under floors later, they look like a nightmare. What's going for them?

[SteveE]

Yes they are pre-stressed and ours were ordered to size.

[SteveE]

Ours are ~ 3.3m. I'm not certain that they are meant to have central supports due to the stressed nature of them and being designed for the span. A central support probably requires separate beams each side of the central support (2x as many shorter beams)

Ordinary concrete blocks are OK with building standards, at least for domestic use, but stronger blocks with heavier kN loadings are available.

+1, exactly how we did our floor and UFH.

There are probably one or two places locally that can make/get them and local builders will be in the know... IIRC, we ordered through "Burdens Civils".

They shouldn't need cutting if the span they're bridging has been measured accurately!

They are not light!

[SteveE]

Try

if they have a branch nearby.

[Andrew]

Don't use that Irish PIR stuff in case it collapses and your floor drops :-)

[ARW]

I have worked on a few. Now if there were service hatches in the suspended ceiling below them you could do the same.

[dennis]

A lot of the houses around here are built with block and beam. It appears to be the cheapest way these days.

They put piles in around the edges and cast a ring around the structure.

Then the beams and the blocks are added.

AFAICS the insulation goes on top and then a screed but I can't say I have paid any attention to it.

I'm amazed that some people haven't noticed that the beams aren't straight. You only have to look at them on the lorry.

[Andy Burns]

I've noticed several Tesco express attached to petrol stations use beam and block ... the ones where the bottles of wine on the shelves go "kling-kling-kling" as you walk down the aisle.

[dennis]

They aren't block and beam then as they are pretty ridged unlike timber floors. Maybe they have put a suspended floor in to get services around?

[The Other Mike]

Significantly less concrete in the strip foundations than a poured slab

Easier to move materials onto site, the beams being the heaviest component at around 150kg a piece (4m)

All services within the building will be in metal trunking and conduit at or above ceiling level with the exception of water and drainage and the electricity that can be on the end of a block run.

Even on a bigger building it would be easier to run services at ceiling level than forming a covered trench/cavity in a concrete floor.

Suspended timber floors have already been ruled out

[Tim Lamb]

In message , The Other Mike writes

I believe builders prefer them because they don't attract attention from BC. (so my architect says)