Beam and block external patio

[DeanoFromTheDock]

Hello all,,

 

just a quick question before I send it off to the enginner, has anybody used beam and block for external use? 
 

as you can see by the pictures I have a retaining wall which is set back from the house.. I’m looking to bring a block and beam from the outer skin of the house and sit on a frame/retaining wall and this use this base as our patio screed over the top and then slab.. 

 

has anyone used beam and block for external use before? What I was thinking of doing is bitumen all external parts of the beam before cladding of some sort to keep it weather proof 

 

any replies would be appreciated 

[Mr Punter]

A friend of mine has done this.  Sloping site and I think they can access a reduced height space under the patio for storage.  Your concrete retaining wall looks good.

[DeanoFromTheDock]

Thank you mr punter.. was a bit of a struggle but we are getting there. It is up to first floor level currently waiting on joists and scaffold after the new year so trying to sort this beam and block idea asap 

 

im only looking at using 4.2m beams build another small wall to carry the end of the beams.. the architect seems to think it will be fine but wants me to check with the enginner. I was just thinking of using a cement wash over the top and screed and patio slab on top.. 

 

but if anyone has any better ideas I’m open to listen? 

[Conor]

We're doing exactly the same. Raised patio out the back of the house, with a storage area underneath. I'm looking at span tables now before sending sketches off to architect and SE. 

 

My thoughts are also firmly on waterproofing. First, flashing against the house, secondly, a cement based tanking slurry over the beam floor. Paving over. The bit I'm worried about is how to get rid of the water on top of the beam floor. Inevitable that water will soak through the pavers and screed, and then sit on the tanked surface. I'm worried it'll be perpetually wet and lead to a horrible slimy surface. 

 

Alternative is to screed with a fall, then tank. Still trying to figure it out.

[Conor]

Actually, the sloped screed with tanking on top then pavers on pedastals is the answer. Just need a route for the water to leave the deck.

[PeterW]

2 hours ago, Conor said:

Actually, the sloped screed with tanking on top then pavers on pedastals is the answer. Just need a route for the water to leave the deck.

+1 to this 

 

Screed can take the camber out of the beams and can be graded with a long board to run to a drain point and then membrane or waterproofing liquid over the top. The slabs on pedestals can then be laid level as any water is draining below them.

[Temp]

Got planning permission? Or will it meet Permitted Development rules?

Edited December 27, 2022 by Temp

[Gus Potter]

11 hours ago, DeanoFromTheDock said:

any replies would be appreciated 

In principal you can use beam and block externally.

 

In Scotland you can (in the right circumstances) have B&B over a a raw soil solum.. i.e no DPM with solum screed. They can stand a damp environment.

 

But there is one big caveat. As a bit of background the Champlain Towers South in Florida that collapsed, I think the documentary is on I Player. There is one school of thought. They had a swimming pool and the slab connected into the main structure. They did not realise that the swimming pool slab was "really tied in" so when it failed it pulled the rest of the building with it.

 

If you asked me to design this I would want to play safe and say.. I want you to make sure that the B&B floor / roof is subject to no more a harsh environment that they would be say in a ground floor. In other words it needs to be waterproofed from above. One main reason is that some folk put salt on their drives and patios in winter weather. Folk may get too keen on fertilising pot plants.. again these chemicals can promote corrosion of the steel in the beams.  Reinforced concrete can protest and this can lead to failure that will drag the house with it.

 

Yes I know you may not do it (use salt etc) but subsequent owners may be unaware.

 

For all @DeanoFromTheDock is cracking on and has a big chunky retaining wall. Looking at the photo the design looks reasonably balanced as the house is not that wide along the road elevation.. but if it was a little wider then it opens up the possibility to make big savings on the retaining wall. Here you use the house to brace the retaining wall at the top and that can be a game changer in terms of retaining wall cost.

 

Depending on the soil you have and the loads on the ground uphill there is a trick you can deploy. We know for example that some CLAY soils can push quite hard horizontally against a retaining wall. This can be great if you are doing a passive build or eco freindly house. You are probably using EPS ayway so can get a good deal on price. What you do is to dig out more of the soil (if you have the space) and replace with EPS.. this takes out a lot of the lateral soil load, you brace against the house (If you are using ICF walls they can offer great stiff sideways/ horizontal support).. in other words you look at the design holistically and get try and get every bit to work most efficiently.

 

Oh but it sounds like I could sell you chalk from the Downs.. but.. here is a pit fall. If you use this trick you have to be sure about how you are going to control and understand the ground water. EPS floats so you need to check for "ballast".. if not you could wake up one morning and find your EPS is now blocking the view from the windows.. not a good look if you are the designer.

 

@DeanoFromTheDock Let us know what your SE thinks.

 

 

 

 

 

 

 

 

 

 

 

 

[DeanoFromTheDock]

Thank you for the replies.. I’ve added another picture.. this span is about 1.5m.. I’m having a galvanised H beam frame being fabricated which will carry the beams from the house. 
 

as the first image.. I’m thinking same again as to tie into to the house, the retaining wall will carry the bull of the load plus I’ve dug a footing to build a small wall block on flat to carry the end of the beam.. I’m looking at 4.2m beams.. this will then become only a patio area no storage.. I was thinking of a slurry screed and to bitumen all external parts of the beams before slabbing on top?? 
 

the other option is timber and composite decking but I don’t really like this idea? What are your thoughts? 
 

I’ll be going to the SE first week of January with my idea 
 

 

[DeanoFromTheDock]

12 hours ago, Gus Potter said:

In principal you can use beam and block externally.

 

In Scotland you can (in the right circumstances) have B&B over a a raw soil solum.. i.e no DPM with solum screed. They can stand a damp environment.

 

But there is one big caveat. As a bit of background the Champlain Towers South in Florida that collapsed, I think the documentary is on I Player. There is one school of thought. They had a swimming pool and the slab connected into the main structure. They did not realise that the swimming pool slab was "really tied in" so when it failed it pulled the rest of the building with it.

 

If you asked me to design this I would want to play safe and say.. I want you to make sure that the B&B floor / roof is subject to no more a harsh environment that they would be say in a ground floor. In other words it needs to be waterproofed from above. One main reason is that some folk put salt on their drives and patios in winter weather. Folk may get too keen on fertilising pot plants.. again these chemicals can promote corrosion of the steel in the beams.  Reinforced concrete can protest and this can lead to failure that will drag the house with it.

 

Yes I know you may not do it (use salt etc) but subsequent owners may be unaware.

 

For all @DeanoFromTheDock is cracking on and has a big chunky retaining wall. Looking at the photo the design looks reasonably balanced as the house is not that wide along the road elevation.. but if it was a little wider then it opens up the possibility to make big savings on the retaining wall. Here you use the house to brace the retaining wall at the top and that can be a game changer in terms of retaining wall cost.

 

Depending on the soil you have and the loads on the ground uphill there is a trick you can deploy. We know for example that some CLAY soils can push quite hard horizontally against a retaining wall. This can be great if you are doing a passive build or eco freindly house. You are probably using EPS ayway so can get a good deal on price. What you do is to dig out more of the soil (if you have the space) and replace with EPS.. this takes out a lot of the lateral soil load, you brace against the house (If you are using ICF walls they can offer great stiff sideways/ horizontal support).. in other words you look at the design holistically and get try and get every bit to work most efficiently.

 

Oh but it sounds like I could sell you chalk from the Downs.. but.. here is a pit fall. If you use this trick you have to be sure about how you are going to control and understand the ground water. EPS floats so you need to check for "ballast".. if not you could wake up one morning and find your EPS is now blocking the view from the windows.. not a good look if you are the designer.

 

@DeanoFromTheDock Let us know what your SE thinks.

 

 

 

 

 

 

 

 

 

 

 

 

That’s a very in-depth reply and way above my limited knowledge but I think I get it 🙈 

 

thank you 

[saveasteading]

1 hour ago, DeanoFromTheDock said:

That’s a very in-depth reply and way above my limited knowledge but I think I get it

So give him a 💙 

[DeanoFromTheDock]

On 27/12/2022 at 11:48, Mr Punter said:

A friend of mine has done this.  Sloping site and I think they can access a reduced height space under the patio for storage.  Your concrete retaining wall looks good.

It’s getting there.. we had to move around 1600t to begin with.. went for the concrete retaining wall and pretty happy tbh.. 

 

the joists and scaffold come first week of January so all systems go.. 

[Gus Potter]

On 28/12/2022 at 12:01, DeanoFromTheDock said:

That’s a very in-depth reply and way above my limited knowledge but I think I get it

All the best. Yes it was a long reply.. then main thing is that if you read my post I was not just writing for you really.. it was for everyone on BH.. we all pinch ideas and discuss design be it planning or all the other issues.

 

If you want more help then post more on your thoughts.

 

If you give a bit on BH you'll find that you get much more in return.

 

 

 

 

 

 

 

 

[Gus Potter]

On 29/12/2022 at 20:47, DeanoFromTheDock said:

It’s getting there..

Can you report back on what your SE says?

 

 

 

 

 

 

 

[DeanoFromTheDock]

On 31/12/2022 at 01:05, Gus Potter said:

Can you report back on what your SE says?

 

 

 

 

 

 

 

yes, i will as soon as i hear anything back... im still waiting but ive taken delivery of 17 beams today so im hoping its a yes haha

[DeanoFromTheDock]

Good evening Gents,

 

Just a quick update on what has been said by the SE 

 

I contacted the block and beam supplier in bristol and asked about external use and for a copy of the data sheet.. they informed me that external use for beam and block is fine.

 

The SE originally way over specked the design for the north elevation balcony (in the pic where the brickie is) he wanted 8" steels to carry the block and beam at 2.1m long... wasn't happy with this as it would of meant having a small step from east side to north side... so i decided to change the design.. on the east side we have 4.2 b&b which will sit on the external skin of the house sit on the retaining wall and ive also built a block on flat wall at 4m to carry the load all agreed and happy with the SE... The only thing he wanted was an 8" lintel to carry the last 3 beams.. i will run a dpc tray for the beams sitting on the external skin of the house blockwork

 

for the north facing balcony we have used 6" galvanised i beams which will now carry a timber frame and have composite on top.. we have built to supports into the house which are sitting on padstones..

 

thank you for the feedback gents  

[DeanoFromTheDock]

[DeanoFromTheDock]

The 2.1m lintel x 215 x 100mm will sit on the corner block work of the house and on the retaining wall to carry the last 3 beams for the patio 

[DeanoFromTheDock]