Beam and block flooring

[osmononame]

Hi all,

 

So due to the height at the rear of our house instead of going for a traditional timber or composite decking area we went for beam and block flooring which would hopefully give us some longevity. The issue we are having is that about 3 of the blocks have broken with light foot traffic already (only installed last week). Surely this isn't normal and you should be able to walk on them without fear of the blocks cracking?

 

I'm waiting on the structural engineer calling me back but it's a but unnerving hence me posting it here. 

[Declan52]

Used to hate block and beam flooring for this very reason. Blocks sometimes have cracks in them and they break. It happens. Just replace them.

[saveasteading]

52 minutes ago, osmononame said:

Surely this isn't normal

Not a problem. they were probably damaged in handling, and the foot traffic is not the real cause.

When the screed goes on top they become very much stronger as it all bonds together.

 

For now, to redcue your concerns,  if you pour over a cement slurry mix and work it into the gaps, the blocks will bind together and not joggle when walked on.

 

Just cement and water in pourable consistency, applied with bucket and broom, or even watering can.

 

You possibly don't even need to replace these blocks, but I would.

[Russell griffiths]

As has been said, blocks would have been broken previously, then laid, crack only appears after a bit of rocking about. 

Pull it out and put a new one in. 

[osmononame]

Thanks for that - we did think it was due to damage when handling the blocks but we have had broken blocks now from 3 separate deliveries and handled them like a newborn when installing them after the first crack but who knows how they were handled before they got to us!

 

There is going to be a storage room underneath and the fear is that a block comes crashing down on your head years down the line - good to know the screed will strengthen everything! On another note the bounce is terrible! I can tolerate it outside but if we had gone for beam and block internally I think I would have been sorely disappointed. Had it not been for access issues I would have probably gone for something like a hollowcore floor.

[Mr Punter]

You can specify less bounce either bigger beams or blocks sideways.

[osmononame]

Yeah we did that. Our beams are doubled in places and also blocks sideway in places. We could have gone for shorter runs and had less bounce (and a compromised room underneath) that way but as things always end up at - budget - decided our fate and we ended up with what we could afford. Not unhappy with it and I knew to expect it - just an observation. Maybe with the screed it'll settle a bit too. 

[saveasteading]

2 hours ago, osmononame said:

the bounce is terrible!

The bounce also reduces dramatically when the screed goes on. I do hope your have a concrete screed next, and not insulation.

 

firstly the blocks will be rather loosely placed and will not contribute the overall strength, unless you fix them as mentioned above.

Secondly, and more importantly, when you add say 100 to the top of a beam it becomes composite and that concrete is now compressing whenever load is put onto the floor. It also spreads the load out further, so onto more beams.

In approximate terms , you double the thickness and quadruple the stiffness.

 

So stop bouncing on it or you may crack more blocks.

 

what is the construction from now?

[DragsterDriver]

Have you grouted it?

 

am I right in thinking this is an outside raised patio/deck?

[Dave Jones]

you are actually using 7n blocks right ?

 

If you have any double beams fill the void they create with conc, really helps stiffen it  all up.

[osmononame]

On 09/10/2021 at 17:32, DragsterDriver said:

Have you grouted it?

 

am I right in thinking this is an outside raised patio/deck?

 

Thats correct and yes its been grouted with a sand and cement mix.

 

2 hours ago, Dave Jones said:

you are actually using 7n blocks right ?

 

If you have any double beams fill the void they create with conc, really helps stiffen it  all up.

 

We just grouted these parts with the same sand and cement mix - should I remove/replace with concrete? I guess now is the time to do it if it will help!

[Dave Jones]

wouldn't worry about it.

[osmononame]

and yes we are using 7n blocks - thats what the structural engineer specified - although the brickies were moaning about the variances in the block sizes - apparently the manufacturer (Patersons) are bad for that! 

[saveasteading]

4 hours ago, osmononame said:

should I remove/replace with concrete?

No. That is the correct process before concreting.

 

Just to confirm, you are concreting over the whole area? how thick?

 

[osmononame]

From  memory about 50mm but would need to check with the structural engineer - we are really tight with the threshold at the sliding doors so dont think we can go much thicker than that.

[saveasteading]

On 09/10/2021 at 14:12, osmononame said:

block comes crashing down on your head years down the line

 

Best remind your SE of the bounce. I would think 50mm will make a huge difference.

 

Although the screed above will hold it all together, even without there is no way the blocks will fall through even if broken.

The crack is a very jagged line and you would have to pull the 2 parts of the block apart about 20mm before it fell The block is held in place at the ends by your preliminary grout or the concrete, so it will sit tight.

Relax.

[markc]

All sound advice. And if you wish to reassure yourself - take a broken block out from below and you won’t worry about them falling again.

[saveasteading]

1 minute ago, markc said:

take a broken block out from below

Or try, then give up, happy that it is tight.

[Mr Punter]

I have found that once the blocks are in and grouted you have to smack the hell out of them to remove one.

[Moonshine]

1 minute ago, Mr Punter said:

I have found that once the blocks are in and grouted you have to smack the hell out of them to remove one.

 

me too, i had to get into the floor void as a guide rope for services got stuck and needed to be freed.

 

I was actually surprised how much effort it took to get one out once grouted

[Temp]

We have B&B on both floors of our house. Has Insulation and screed on top and plasterboard below. Never had any blocks crack or fall down. Love it for the solid feeling. 

 

[phatboy]

Sorry to revive an old thread, but it's right on topic.

 

I see above a suggestion of just grouting with cement and water.... id not heard of that before.  I was thinking of 4:1 sand cement, with a lot of water and plasticiser.  Ill be doing it as soon as the weather cools down a little!

 

Any advice appreciated, it seems this job can be easy, or a complete nightmare!?

[Canski]

That’s what we do but using sharp sand. Wet the floor before pouring it over and have a big stiff brush to move it around. It’s easy you’ve just gotta keep it moving. 

[Roundtuit]

Definitely grout; it's structurally important for the block and beam and worth spending the time to do a good job. My builder did a bit of a slapdash job tbh.  I ended up have to chip off a load of 'snots' so the insulation would sit properly flat and fill the bits he missed.  Do it straight away after the block and beam goes down, or all the gaps will get full of crap and leaf debris, particularly as we head into an early autumn.

[saveasteading]

5 hours ago, phatboy said:

just grouting with cement and water.... id not heard of that before.

Yes , if the blocks are tight together then cement slurry will go between whereas s and c will sit on the top. For bigger gaps you need  s and c.

So I would do the cement slurry first, as it is just a watering can (without rose) and poured over the joints. It will dry out almost immediately. Then the s and c can go in the bigger gaps.

 

Doing the slurry first can lock loose or cracked blocks together and avoid damage, and is a lot easier than brushing. I seem to recall it was an official recommendation from the B and B manufacturers but maybe it was just me.

I now recall that by closing all the little gaps it stops clients fretting when looking up from a ground floor and seeing light through the floor.