Block and beam construction for decking

P

pal123

Member
I'm looking for 'no wood' decking - so no wood whatsoever regardless of whether the wood is pressure treated.

There are 4 x concrete pillars. The existing wooden decking is partially rotted.

I came across this 'block and beam' construction for a suspended floor. A youtube video is here:
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I think that this block and beam construction could be used for a decking as the concrete pillars are there. and go deep into the earth - I would need to check how deep and how strong these pillars are. The framing would need 2 x large lintels to span the two concrete pillars. And then 8-12 thinner lintels spanning across the two larger lintels. Then blocks would fit between the thinner lintels. Finished with a cement render and drain holes to drain holes.

Any idea if I can use this block and beam method for the decking?
 
You could but would it be the most cost efficient way to install it?
How high does it need to be? Are you using an all composite system? Or are you talking about just block n bream finished look?
Bnb I’ve done hase been constructed same way as suspended timber floors, small foundations bnb built off that, depending on height n size needed slab might be more suitable? Not the easiest thing to make look pretty
 
Resmond said:
You could but would it be the most cost efficient way to install it?
How high does it need to be? Are you using an all composite system? Or are you talking about just block n bream finished look?
Bnb I’ve done hase been constructed same way as suspended timber floors, small foundations bnb built off that, depending on height n size needed slab might be more suitable? Not the easiest thing to make look pretty
Click to expand...

The decking only needs to be a max of 20cm above the pillars. The current decking is about 25cm above the pillars. The ground slopes downward so the grass section stops then the decking starts.
Not looking to use composite as they are expensive and require maintenance. I'm talking about just using lintels and blocks (all cement) and zero wood and zero composite.

Only reason I'm suggesting blocks is that blocks can be slotted between lintels (which have a L cross section so hold the blocks). Don't think slabs can be slotted the same way. It will use a render finish and drain holes being drilled with painting after.
 
Ok a drawing might help, if the concrete posts are secure then they’re probably not the worry it’s more the span between them taking tge two long concrete lintels that you’re then planning on putting bnb on top of… usually there’s a longe span but only 500mm spacing.. basically you might need more posts/supports
 
Isn’t putting the beams straight onto the lintels pointing loading, which I believe you shouldn’t do with concrete lintels.
Just saying ;)
 
There's nothing wrong with the theory: you can span 4.5m or so with standard beams at maximum spacing and more if the beams are closed up. Obviously there are high loads at the beam ends which need consideration.

I personally think it would look seriously weird and have to ask why?? If you're happy with a concrete finish then put in a slab and either leave as finished or expose the aggregate (which can look really good). Or slabs, crazy paving, pavers etc
 
You're dead set not to use composite but don't say why.
FWIW, I used composite on a deck that I created over 20 years ago and it's still as solid and good looking as the day I finished it. No rot, UV damage, or degeneration of any description in all that time. It gets pressure washed once every 5 years or so, but that's just to make it less slippery during winter. (I would have the same chore if I had used your system, as it too would develop mosses).

If you've ever worked with the B&B systems you're looking at, you'd know that the blocks are not completely free of motion on the beams. They wobble ever so slightly as you walk on them. This is normal, and not a issue at all when they have a good strong slab or screed laid on them. If however you just put a render on them they would be cracked within a short while.

The other thing to note is that when some time out in the future you decide to sell the property, will your style of deck add value or detract value from it? Personally I'd be looking for a steep discount on the property because one if the first things I'd need to do is pay to get rid of it all. Hey, to each his own! :D
 
Resmond said:
Ok a drawing might help, if the concrete posts are secure then they’re probably not the worry it’s more the span between them taking tge two long concrete lintels that you’re then planning on putting bnb on top of… usually there’s a longe span but only 500mm spacing.. basically you might need more posts/supports
Click to expand...

Here's a link to a JPEG drawing (bird eye/top down view): https://e1.pcloud.link/publink/show?code=XZrbgRZ0bsy8P53Xuj2TCXLFBdIwVpiyAdk

This only shows the position of the 4 x concrete support pillars and the earth retaining wall. All pillars and the earth retaining wall are used to support the current wooden beams.

The decking span is about 4.5m x 4.3m
 
Abrickie said:
Isn’t putting the beams straight onto the lintels pointing loading, which I believe you shouldn’t do with concrete lintels.
Just saying ;)
Click to expand...
Here's a link to a JPEG drawing (bird eye/top down view): https://e1.pcloud.link/publink/show?code=XZrbgRZ0bsy8P53Xuj2TCXLFBdIwVpiyAdk

This only shows the position of the 4 x concrete support pillars and the earth retaining wall. All pillars and the earth retaining wall are used to support the current wooden beams.

The decking span is about 4.5m x 4.3m
 
Slightly confused reading back as you say you want ‘no wood decking’ and then that you don’t want to use wood in any form, or composite either so I’m
Not sure what you’re actually building. Sounds like you want some sort of block and beam suspended patio. In which case don’t. Far too much movement as already pointed out. Either build a composite deck or build a raised patio. The two aren’t really interchangeable.
 
Truckcab79 said:
Slightly confused reading back as you say you want ‘no wood decking’ and then that you don’t want to use wood in any form, or composite either so I’m
Not sure what you’re actually building. Sounds like you want some sort of block and beam suspended patio. In which case don’t. Far too much movement as already pointed out. Either build a composite deck or build a raised patio. The two aren’t really interchangeable.
Click to expand...
Really very simple: NO wood.

A block and beam is cheaper and longer lasting.
 
Maybe cheaper upfront costs (assuming you have taken all the labour and materials into the calcs), but maybe not in total cost of ownership, which includes the amount of value it adds to or detracts from your eventual selling price.
 
As abrickie pointed out you cant point load concrete lintels, possibly you could use steel, ideally you’d dig foundations then build dwarf walls and build your bnb off that in a similar fashion to a suspended timber floor..
The general consensus here is it’s not an ideal method of construction for what you want to achieve..
Raised patio is probably what you want as suggested, chuck a load of hardcore down, blind it, concrete then finish however you like, resin, slabs, polished concrete etc..
 
pal123 said:
Really very simple: NO wood.

A block and beam is cheaper and longer lasting.
Click to expand...

Longer lasting certainly. Just not sure what you’re hoping to build. From description it’s some sort of random suspended concrete block floor with render on top. It won’t last five minutes before it cracks. Have a look at how they build concrete floors in new steel framework building. That might be a better option.
 
Truckcab79 said:
Slightly confused reading back as you say you want ‘no wood decking’ and then that you don’t want to use wood in any form, or composite either so I’m
Not sure what you’re actually building. Sounds like you want some sort of block and beam suspended patio. In which case don’t. Far too much movement as already pointed out. Either build a composite deck or build a raised patio. The two aren’t really interchangeable.
Click to expand...
How would it move? I would bolt/fix the lintels into place.
 
Resmond said:
As abrickie pointed out you cant point load concrete lintels, possibly you could use steel, ideally you’d dig foundations then build dwarf walls and build your bnb off that in a similar fashion to a suspended timber floor..
The general consensus here is it’s not an ideal method of construction for what you want to achieve..
Raised patio is probably what you want as suggested, chuck a load of hardcore down, blind it, concrete then finish however you like, resin, slabs, polished concrete etc..
Click to expand...

The bottom two thicker support lintels would be laid onto the four concrete pillars. Then several thinner lintel would be laid over the thicker support lintels. How is that point loading? The lintels would be loaded in the same way as a suspended floor - approx 4.5m unsupported then support at 44cm (pillar 1) and 44cm (pillar 2) either end.

Steel beams? Not sure what you mean by steel

Would a raised patio need a retaining wall? There is a load of earth underneath the existing decking which would need to be removed first. Then a retaining wall build then infilled
 
pal123 said:
How would it move? I would bolt/fix the lintels into place.
Click to expand...

The blocks are laid loose and will move. The render will crack. But give it a go. Be interested to see the process. The fact that it’s not an accepted method doesn’t mean you shouldn’t do it. Loads of stuff that isn’t ‘correct’ will work fine. Just be prepared to experiment and change tack if it doesn’t work as expected.

It might work if you use it as the base for a concrete pour which will avoid the issue of movement but it’s an odd way of going about it. If you want a concrete type finish then do as has already been suggested and build a surround, fill with hardcore and do your concrete pour.
 
rogerk101 said:
You're dead set not to use composite but don't say why.
FWIW, I used composite on a deck that I created over 20 years ago and it's still as solid and good looking as the day I finished it. No rot, UV damage, or degeneration of any description in all that time. It gets pressure washed once every 5 years or so, but that's just to make it less slippery during winter. (I would have the same chore if I had used your system, as it too would develop mosses).

If you've ever worked with the B&B systems you're looking at, you'd know that the blocks are not completely free of motion on the beams. They wobble ever so slightly as you walk on them. This is normal, and not a issue at all when they have a good strong slab or screed laid on them. If however you just put a render on them they would be cracked within a short while.

The other thing to note is that when some time out in the future you decide to sell the property, will your style of deck add value or detract value from it? Personally I'd be looking for a steep discount on the property because one if the first things I'd need to do is pay to get rid of it all. Hey, to each his own! :D
Click to expand...
Cost really composite costs a bomb and replacement parts are a lot. The render would go over the beams and blocks - so would that not connect and bind together the blocks and beams.
 
Resmond said:
As abrickie pointed out you cant point load concrete lintels, possibly you could use steel, ideally you’d dig foundations then build dwarf walls and build your bnb off that in a similar fashion to a suspended timber floor..
The general consensus here is it’s not an ideal method of construction for what you want to achieve..
Raised patio is probably what you want as suggested, chuck a load of hardcore down, blind it, concrete then finish however you like, resin, slabs, polished concrete etc..
Click to expand...

The existing concrete pillars act as dwarf walls now
 
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