Browsing these recently and most manufacturers have a panel which fits between the beams and one which goes over the top. Like this. 

 

But then I see a manufacturer who does it with the insulation underneath and in-between and i think you end up with cold bridges where the beam bears onto the supporting wall. Have they allowed for this in their u values? I suppose you could mitigate with a sheet over the top but just seems a massive design error to me. Is it that the bridges are inconsequential on a large floor or do others agree? I'm just trying to guess why they would design like this?

Beamshield is the same, and also covers the underside.

 

I would go for the system that keeps cold air from the ventilated cavity getting to the beams, for obvious reasons, and then use PIR over the top.

 

I see a lot of developer sites using the cheaper / faster (poorer) version so there’s your answer , but it is good to see some at least trying.
 

Using blocks is just neanderthal level building, with the cost and grunt of slinging lorryloads of them around site.

 

Developers have gone with this to reduce costs, the extra insulation is just an accidental side effect of their bean-counting. 

 

The beams will always bear on to blockwork due to the point loadings / weight upon them, and the cold bridging is negligible. 

20 minutes ago, Oz07 said:

manufacturer who does it with the insulation underneath 

This has been around for decades and is simple and effective. I've never used it and so haven't checked the relative cost.

22 minutes ago, Oz07 said:

Have they allowed for this in their u values? 

They will give a a value for a central cross section. The overall effect of the beam bearings depends on the size and shape of the building and is reality, not a flaw... any beam has the same.

The main benefit of this is in insulating under the beams, in vacant space, and saving insulation above.

 

Best is to work out the relative costs every way , if inclined.

 

At the internal wall I assume the eps block is cut to fit.

 

Another advantage will be the finish. With concrete blocks they don't always sit tight and you have to brush a sandy mortar into the gaps.

And lighter to handle of course.

 

 

I think you guys are missing what im saying. The bottom photo is how that system is finished. As in the slab sits directly on top of those beams which bear directly on top of the masonry at the walls. So an unmitigated cold bridge. The top system has the underside of the beams exposed but has a 75mm (or thicker) sheet of insulation over the whole top so no unmitigated cold bridge. It just seems a massive own goal to me but perhaps I don't understand cold bridges correctly?

I agonised over things like the cold bridges with insulated bnb floors then I did the numbers on a solid floor with lots of underfloor insulation.  I know bnb floors bypass a lot of underground issues and are often the only option (as in our last house) but if you’ve the choice why not check the relative costs of a solid floor for your build.  

I did ground bearing last place but got some apple trees im lopping so think gonna play safe with suspended

4 hours ago, Oz07 said:

you guys are missing what im saying

Not at all.  There is a cold bridge but it is not completely cold if thought through with insulation above.

A building is a cold bridge between indoors and outdoors... but it is relative.

 

4 hours ago, Oz07 said:

play safe with suspended

If near trees then the foundations will be deep and the trees won't affect the slab.

The main downside of  suspended floor is the essential draught under it. You lose the benefit of the natural insulation of the earth. 

3 minutes ago, saveasteading said:

Not at all.  There us a cold bridge but ig is not completely cold if thought through with insulation above.

A building is a cold bridge between indoors and outdoors... but it is relative.

 

If near trees then the foundations will be deep and the trees won't affect the slab.

The main downside of  suspended floor is the essential draught under it. You lose the benefit of the natural insulation of the earth. 

The system is designed by manufacturer. That bottom one is the finished article excluding dpm. Literally finished floor slab. On top of concrete beams which bear onto walls which touch the ground and are exposed to outside air. Of course you can potentially mitigate with insulation on top but who knows if then complies with bba cert. At least the top system has a nice chunky 75mm sheet on top of beams before concrete

Also certain trees mean deeper foundations which mean suspended floor is the better option incase of heave. 

55 minutes ago, Oz07 said:

I think you guys are missing what im saying. The bottom photo is how that system is finished. As in the slab sits directly on top of those beams which bear directly on top of the masonry at the walls. So an unmitigated cold bridge. The top system has the underside of the beams exposed but has a 75mm (or thicker) sheet of insulation over the whole top so no unmitigated cold bridge. It just seems a massive own goal to me but perhaps I don't understand cold bridges correctly?

The floor edges are dealt with as a linear thermal bridge separate from the insulation (& Uvalue) in the general floor area. The ground floor/wall junction is a difficult one when preventing/minimising the thermal bridge. This is more difficult with a suspended concrete slab that bears on inner masonry - 'overlapping' the cavity wall and floor insulation is one option. This is further complicated with beam and block. Relatively simple where the beams run parallel to the wall (2D thermal analysis) but probably requiring a 3D thermal analysis where the beams run into and bear on the wall. Again extending any cavity insulation to well below the floor insulation will help.

1 hour ago, Oz07 said:

suspended floor is the better option incase of heave. 

A bold assertion without knowing the detail.

Everything on its merits.

Its not that bold. A normal ground bearing floor is susceptible to heave, suspended one less so. I have trees very close to proposed house. Better to plan for the worst. 

 

I started the thread as I was interested in the difference between the cold bridges on the 2 different systems. I wasn't really looking for a discussion on whether to use ground bearing or suspended floor. This always happens on this forum. I can see why it has quietened down with ai. 

3 hours ago, Oz07 said:

The system is designed by manufacturer. That bottom one is the finished article excluding dpm. Literally finished floor slab. On top of concrete beams which bear onto walls which touch the ground and are exposed to outside air. Of course you can potentially mitigate with insulation on top but who knows if then complies with bba cert. At least the top system has a nice chunky 75mm sheet on top of beams before concrete

I did one in Gravenhill and the B&B had regular blocks, and then we put 200mm of PIR and 100mm of concrete; reinforced by 2 layers of mesh.

 

The design and storey rods help you to calculate how low the B&B needs to be set down to allow the extra insulation. 
 

75mm of EPS is pretty crap. 

35 minutes ago, Nickfromwales said:

I did one in Gravenhill and the B&B had regular blocks, and then we put 200mm of PIR and 100mm of concrete; reinforced by 2 layers of mesh.

 

The design and storey rods help you to calculate how low the B&B needs to be set down to allow the extra insulation. 
 

75mm of EPS is pretty crap. 

75 on top would be 225 in total with the 150 between beams. I think you can up the spec of the top sheet to achieve .08 u value according to the websites. 

 

But again we are proving my point here. The thread wasn't set up to debate whether beam and block is good or not. Just what appears to me the glaring cold bridge in one of the options above compared to the standard way these 'warm' b&b floors usually work. 

3 hours ago, Oz07 said:

I can see why it has quietened down with ai. 

No offence was intended, and I, probably others too, are aware that a  discussion, even when off course.  may be looked at by many more people than we see.

A tweak on the rudder can remind everyone of the original point.

 

ai can sometimes be very wrong. It picks up info regardless of source.

I don't think ai wil offer any recourse if a fault develops in your buiding.

we meanwhile do our best and can wander off the path sometimes. 

 

Back to your question again. Yes that is a cold bridge but also is with the special blocks which underlap the beams. It can be designed out in other ways.

I did block n beam with standard concrete block and insulation on top, I looked at all these insulated types and concluded that they had two many faults. 
harder to construct being a major one, standard block n beam is very fast and easy. 

cost also, if buying a large quantity of blocks you can get the price right down. 
 

the only upside I can see to these insulated systems is the height you gain, if you only need to put a 75mm cap sheet on then you save 75mm in floor build up, but that’s hardly a big issue. 

9 hours ago, Oz07 said:

But again we are proving my point here. The thread wasn't set up to debate whether beam and block is good or not. Just what appears to me the glaring cold bridge in one of the options above compared to the standard way these 'warm' b&b floors usually work. 

In my daytime role I provoke discussion, rake over everything robustly, and most of the time this is done inoffensively, to get all the options and possibilities on the table.

 

Some of my clients don’t know what they want because they don’t know their options; pros cons and caveats included.

 

You’ve been a member since 2016, so are either benefitting or are suffering in silence here. 🤷‍♂️. 
 

Peoples hunger for inaccurate quick fixes (aka AI) is the sum of modern day society, and even when they see a statement saying the information may be inaccurate they still bank their life on it.

 

After a decade on here, it’s a joy to hear you dismiss all the hard work, time, and effort that the volunteer staff have put in (for free) in some stupid attempt to help some folk out whom we’ll likely never meet or hear from again.

 

75mm of poor insulation over a cold ventilated block and beam substructure is crap, which is the truth. It is a part of an attempt to provide comprehensive feedback to allow you to amass these responses and form an opinion and take the project on admirably for the best outcome possible. 
 

If these digressions offend you so, then that’s an issue your side, as we don’t post here for popularity; facts are facts, take them or leave them, or ask AI which is the best, impartial website that is free to join is.

 

Let me save you asking “it”. 
 

 

PS, thanks for the ridicule. Much appreciated. 

11 hours ago, Russell griffiths said:

I did block n beam with standard concrete block and insulation on top, I looked at all these insulated types and concluded that they had two many faults. 
harder to construct being a major one, standard block n beam is very fast and easy. 

cost also, if buying a large quantity of blocks you can get the price right down. 
 

the only upside I can see to these insulated systems is the height you gain, if you only need to put a 75mm cap sheet on then you save 75mm in floor build up, but that’s hardly a big issue. 

A good benefit is reduced dig out compared to normal b&b with closer matching ground levels. Think you can get the difference between ground level outside and under slab to around 300mm

9 hours ago, Nickfromwales said:

In my daytime role I provoke discussion, rake over everything robustly, and most of the time this is done inoffensively, to get all the options and possibilities on the table.

 

Some of my clients don’t know what they want because they don’t know their options; pros cons and caveats included.

 

You’ve been a member since 2016, so are either benefitting or are suffering in silence here. 🤷‍♂️. 
 

Peoples hunger for inaccurate quick fixes (aka AI) is the sum of modern day society, and even when they see a statement saying the information may be inaccurate they still bank their life on it.

 

After a decade on here, it’s a joy to hear you dismiss all the hard work, time, and effort that the volunteer staff have put in (for free) in some stupid attempt to help some folk out whom we’ll likely never meet or hear from again.

 

75mm of poor insulation over a cold ventilated block and beam substructure is crap, which is the truth. It is a part of an attempt to provide comprehensive feedback to allow you to amass these responses and form an opinion and take the project on admirably for the best outcome possible. 
 

If these digressions offend you so, then that’s an issue your side, as we don’t post here for popularity; facts are facts, take them or leave them, or ask AI which is the best, impartial website that is free to join is.

 

Let me save you asking “it”. 
 

 

PS, thanks for the ridicule. Much appreciated. 

I don't know why you think I'm personally attacking you. I'm just giving valid criticism of what often happens on the forum lately. Someone will start a topic saying let's discuss A or B then C gets bought up. Again I can understand why in some cases but this topic didn't really warrant it. Also I think its disingenuous to say 75mm of insulation over a poor b&b floor is crap. These systems have 150mm between the beams then either 75 or 150 over the top. They can hit or better the 2022 u values of .13 for floors. I dont think .13 is crap by any stretch of the imagination. With this project im not going to start agonising for weeks trying to improve u levels by a certain percentage. It sends you mad. I'd much rather accept a certain running cost to the house and focus my efforts elsewhere. 

 

Again sorry if I offended you the forum has changed a lot since the earlier days. I also believe ai does have a place for answering quick queries. There is no guarantee but the same can be said with anonymous strangers on forums. 

Hi Folks,

Didn't want to create a new thread for another suspended concrete floor insulation question so I hope you don't mind me hijacking this old one.

I currently have suspected suspended concrete flooring in a couple bedrooms and the corridor of my bungalow. The exact construction of the floor is unknown, but it's raised, has a void under it, sounds & feels closer to solid concrete and it sure doesn't feel like suspended wood that I have elsewhere in the house. The floor make-up in the bedrooms is a layer of very old tiles, then underlay + carpet. The corridor has been re-done professionally under previous ownership and looks like a layer of screed (possibly over old tiles) + glued-on LVT, which makes it a very cold floor to walk on.

I'm eyeballing my options to add some floor insulation before I re-decorate the bedrooms and would really appreciate your advice.

Door frame clearance currently is 196cm. Internal walls construction is solid brick, which may make it difficult to raise the clearance to accommodate a raised floor. There's perhaps an extra 10-15mm that I can gain by knocking off the top of the wooden door frame and replacing it with a thin decorative veneer as an easy win.

I don't want to mess with the old tiles, as, given the age of the property, tiles & adhesive might be ACM.

My thinking is along the lines of 25mm PIR (not sure if I need wooden battens between them), then a layer of 8-12mm ply (is that sufficient?), then 2mm underlay & 4mm LVT or 6mm laminate. Perhaps a DPM needs to be placed below or above the PIR?

A total of about 40mm increase in floor level, which potentially sounds like a lot of work for marginal insulation gains and dodgy 193cm door clearances?

Are there any sensible alternatives to keep it under 40mm?

The fallback option is to just lay new carpet with thicker underlay in the bedrooms and replace corridor 2mm glue-on LVT with something like 2mm underlay + 6 or 8mm SPC LVT which I had in my old house and which felt very warm to the foot, so I'm guessing it's got very decent insulating properties. Or just SPC LVT everywhere.

The fallback option results in better door clearances and better quality flooring compared to thinner LVT and laminate.

Your thoughts on how to improve this without resorting to a bulldozer or a concrete breaker are very welcome.

Thank you.

The 12mm ply will deflect terribly, at a minimum you need 18mm and it needs to be tongue and groove so it spreads the load evenly. You need to glue the joints in the boards so the finished floor is in effect one big sheet.

You could use a thinner insulation something like 18mm xps then 18mm chipboard flooring.

Thank you very much.

Looks like there's a combined solution out there already:

https://shop.panelsystems.co.uk/product/styrofloor?attribute_pa_group=styrofloor&attribute_pa_product-name=styrofloor&attribute_pa_length=2400&attribute_pa_width=600&attribute_pa_thickness=68&attribute_pa_unit-of-sale=each

I'm planning on sealing any gaps along the walls for draft proofing. What would be your advice for extra DPM?

43mm XPS+boards, 2mm underlay, 8mm laminate - puts me at about 55mm floor level increase with doorways going down to 191-192cm 🤔

Worth the extra cost & effort, or am looking to waste money to I add a lot of height for very little insulation value?

Its not going to be worth the effort. Look to improve the property elsewhere

The styrofloor principle is relatively simple but you are only getting a thin layer of polystyrene. That page avoids saying how thin, which suggests to me that it isn't impressive.

Carpets with an underlay is the easy way.

Yeah, but carpets in kids' bedrooms can get very dirty very fast, and carpets in a corridor won't survive a fortnight.