Integrated Concrete Beams
Building with Durisol, Quadlock or any other ICF blocks? Here’s how to tackle the floors.
If there’s one thing that adds character, and value, to your self build home it’s a row of massive wooden beams across the ceiling. The trouble is they can be expensive, very heavy and sourcing could slow down your project.
Another desirable thing is a solid concrete first floor; low noise transmission, high thermal mass and suitable for under-floor heating. The trouble is the shuttering required is elaborate and expensive both in materials and time and once the floor is poured there is usually more work involved in boarding, plastering or some other finishing. Concrete block and beam systems look easier but you do need to be very organised and get delivery of exactly the right beams and after paying for heavy lifting gear they won’t look like a cheap fix, and again there will be final finishing to do. Plastering and painting ceilings – no thanks.
Never fear, help is at hand. The Original Twist Integrated Concrete Beam system is so suitable for the self builder that it is hard to consider anything else.
Make up the wooden beams as shown in this cross section. The blue and yellow bits are your choice of regular timber from your local supplier. The slots sawn out of the yellow sections are for wiring channels and it makes sense to insert the wires while the beam is being assembled. The threaded studding stops the beam spreading when the concrete pours in and is part of the construction with the outside acorn nuts making a decorative feature. Use a spindle moulder or router to round off the edges and then apply your choice of finish after distressing with chain, hammer, belt sander etc. You will see that the yellow sections stick up by the thickness of your floor planks and make a perfectly curved transition between the concrete floor and the integral ‘I’ beams. The rebar at the bottom of the ‘I’ section needs to be held in position prior to the pour and this can be done easily and cheaply with pairs of cup hooks screwed into the bottom plank. Use cable ties across each pair to hold the rebars in. Finally, paint the inside of the beam to isolate it from the wet concrete. The beams are then ready to be placed in position, typically on a one metre pitch (Durisol blocks are half a metre wide) and each propped with one or two Acrow props.
The floor planks can be cut and finished at ground level before fitting between adjacent beams. Now is the time to fit any pockets for spot lamps and take the wiring back towards the slots pre-cut in the main beams. The floor planks need to be strong enough to resist the weight of the concrete without sagging; they don’t need to be jointed together as a layer of building paper over the top will stop any leaks. Unlike concrete blocks they are light and easy to pass up to the man above.
Now after putting down some mesh over the beams and planks the floor is ready to pour. If you are using ICFs like Durisol for your walls you should cut out large slots on the inside face to take the beam ends and then the pour for the walls and the floor can be done at the same time. Note that you can walk on the floor while you start pouring the wall so there is no need for scaffolding. The outside of the Durisol blocks sets the top level of the floor so you don’t even need any shuttering. Once the pour is done and set, the walls and floor are all integrated with the homogenous ‘I’ sections in the beams giving enormous strength and stiffness. The ‘I’ section parts of the floor could be up to 360mm deep which makes them into a row of significant beams in their own right. At this point the lower part of the house is waterproof which makes for a good working environment from which to finish off the rest of the house.
Nothing much to do now. Just take down the props then go down to the pub to celebrate all the money and time you’ve saved. There is no ceiling finishing to do, no shuttering to take down, even the lights are fitted and wired. And all this was done with simple hand tools and without waiting for special parts to be delivered. And just look; lovely lovely beams.
A small spacer between the top of the beam and the floor joists will create a gap to house some LED strip lights. As you have a lovely wooden ceiling you might as well show it off.
In the same way that ICFs make wonderful poured supports for the beams don’t forget that support posts can be made really cheaply out of plastic drain pipes filled with rebar and concrete.
N.B. Wood shrinks. A tiny air gap could eventually appear between the concrete floor and the wood floor. A very thin elastic membrane between the floors (instead of the building paper) will prevent any ‘thwack’ as the upper floor is walked on.
While this system is great for under floor heating, I’m really not in favour of it for bedrooms as it is a big waste of money for an unwanted result. More on that in the eco-heating link below.
N.B. I just liked this idea so much that I had to share it but I am no builder so do your own evaluation for suitability.
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‘Dream House – Down To The Details’ 101 things you should have thought of. here:-
Heating for your eco-house
For another example of down to earth thinking, this time on heating systems, have a look at:
You really should get this right and there are many wrong turns where multiple energy sources are integrated.
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