Raft disaster! Help, advice and likely copious amounts of Gin needed!

[lizzieuk1]

Oh lord, I could cry. 

Sorry its long but please read!

 

So, having thought we'd have no issues with AFT (insulated raft supplier) going out of business we have, according to the law of sod, now got a rather large issue. 

We've, for various reasons (some self influcted, others not) been quite delayed starting laying our insulated raft so, it has been safely stored away in one of our barns for the past (eek!) year.

 

After carefully completing the ground works/drainage over the past few months, with what felt like a ship load of pea gravel! all has been fine, levels all spot on and finally, this week we started laying it all out.

 

So now we are at the issue. 

 

We carefully installed the perimeter L Elements around 3 sides before we realised, oh bu##er, we don't have enough, we are 3 short! 

 

I initially thought it was our fault for not counting them all on delivery (stupid, things were a bit chaotic on the day unloading a huge lorry) but, after cross checking paperwork it looks like AFT didn't actually order enough from Benders!

 

On the original quote from AFT we have 45 detailed but, after double checking the order directly with Benders, there's only 42! 

I hadn't expected to need to check AFT had actually ordered enough, assuming it's their mistake and not Benders as, obviously, I can't see what AFT sent to them!

 

So, here we are up the proverbial creek without a paddle. Falling at the first hurdle, not a great start!

 

So, please, opinions/advice on how to get us moving again. 

 

As we see it options are:

 

1. Contact AFT for help? 

I have a contact number (that works) for Greg, but not sure how far we'll get. Left a voicemail & text yesterday (after speaking to him earlier in the day about a minor corner detail, before we found the big issue!) but no reply yet (not a great sign)

 

2. Try to source from someone else, Benders are Sweden based and don't supply direct but, maybe someone in the UK is getting a delivery from them we could piggy back on. Buildlite/Greenraft i think use similar elements but time likely a big issue here.

 

3. Manufacture our own L shape elements - doesn't look too tricky (am i being naive here?!) Xps base glued to eps upstand then render the exterior. Then, shutter like mad before concrete pour to ensure they don't fail. Hubby keen on this option as likely much quicker.

 

4. No idea what else, all suggestions gratefully received!

 

P.S is it too early for Gin?!

 

[-rick-]

First, don't panic!

 

8 minutes ago, lizzieuk1 said:

3. Manufacture our own L shape elements - doesn't look too tricky (am i being naive here?!) Xps base glued to eps upstand then render the exterior. Then, shutter like mad before concrete pour to ensure they don't fail. Hubby keen on this option as likely much quicker.

 

I think this is an easy option. The AFT forms are just a way to make the concrete laying easy, producing the same shape with standard (correct spec) XPS should be fine. Maybe reinforce with wooden forms on the outside if not sure of the glue strength. If you look at people in Sweden laying these types of foundations they don't necessarily use preformed XPS anyway, just build up from sheet.

[JohnMo]

I would look to make your own bits. As mentioned above once you get your head clear of the initial panic, suitable grades is eps and xps and some bracing and away you go.

[Nestor]

19 minutes ago, lizzieuk1 said:

P.S is it too early for Gin?!

If you are at the Airport, then no otherwise standards must be maintained.

 

As above, great advice to make your own and move on.

[Mr Punter]

Another vote for make your own.

[saveasteading]

Agreed make your own. The priority is strength as insulation can be sorted after.

[ChrisJ]

Make your own as needed, technically not right, but hey, we've all gone over the speed limit more then once and not an issue

 

And yes it's 12pm somewhere in this world - pour away, but make mine Gin and Lemonade

 

 

[Square Feet]

I'm hoping to make my insulated slab entirely myself using sheet materials so I would say No 3 and bash on.

[saveasteading]

If you put up a drawing showing the cross section and location, then we can maybe advise on the method.

[IanR]

1 hour ago, lizzieuk1 said:

1. Contact AFT for help? 

I have a contact number (that works) for Greg, but not sure how far we'll get. Left a voicemail & text yesterday (after speaking to him earlier in the day about a minor corner detail, before we found the big issue!) but no reply yet (not a great sign)

 

2. Try to source from someone else, Benders are Sweden based and don't supply direct but, maybe someone in the UK is getting a delivery from them we could piggy back on. Buildlite/Greenraft i think use similar elements but time likely a big issue here.

 

3. Manufacture our own L shape elements - doesn't look too tricky (am i being naive here?!) Xps base glued to eps upstand then render the exterior. Then, shutter like mad before concrete pour to ensure they don't fail. Hubby keen on this option as likely much quicker.

 

4. No idea what else, all suggestions gratefully received!

AFT used to use Springvale EPS, in the UK for their UK orders. I hadn't realised they'd changed to their Swedish Supplier for the UK orders. I did get extras from Springvale, but needed Olaf to "OK" the order. I assume the AFT <-> Springvale relationship turned sour???

Have you got Olaf's details? He still has the AFT domain, so his email is likely still operating. I believe I have his UK mobile, but he did use it in when in Sweden - have you got that?

If you are not in a rush, I'd try Olaf to supply the correct sections - no question on insurance cover then.

If not then I'd make them up myself, but you need to use the EPS200 or EPS300 spec that L Formers were specified in.

[IanR]

25 minutes ago, Square Feet said:

I'm hoping to make my insulated slab entirely myself using sheet materials so I would say No 3 and bash on.

Interesting... Are you doing the calcs, or a 3rd party SE, and does their insurance cover you for the DIY approach? I couldn't find a way of avoiding being "locked in" to a specific supplier and being charged a premium for the EPS - although I was happy in the end (after a long search and negotiation) the premium wasn't too high.

[-rick-]

18 minutes ago, IanR said:

Interesting... Are you doing the calcs, or a 3rd party SE, and does their insurance cover you for the DIY approach? I couldn't find a way of avoiding being "locked in" to a specific supplier and being charged a premium for the EPS - although I was happy in the end (after a long search and negotiation) the premium wasn't too high.

 

The formwork is really just a short cut/timesaver. It's the engineering that really matters. I had thought that some raft suppliers give you the choice of just using them for the engineering or for both that and the formwork.

 

Where rafts are more common I believe that using the precut XPS formwork is still not the norm with most making it from 100mm sheet.

[IanR]

1 minute ago, -rick- said:

I had thought that some raft suppliers give you the choice of just using them for the engineering or for both that and the formwork.

 

That wasn't my experience in 2016/17. The Engineers doing optimised rafts, like AFT, ie. 100mm thick in the main, with a deeper ring beam and single layer mesh, were all packaging up their calcs with EPS Supply. Some were also packaging concrete, steel and labour for installation.

If there are now Engineers that will sign off an optimised raft from sheet EPS and only charge for the calcs then that is a benefit. Can anyone share some names?

[JohnMo]

56 minutes ago, IanR said:

Are you doing the calcs, or a 3rd party SE, and does their insurance cover you for the DIY approach?

But only the steelwork and concrete are structural - the insulation is just that, insulation. It does provide support to the wet concrete while it cures so is just form work that remains in place. It an insulated slab at the end of the day.

[Nickfromwales]

2 hours ago, lizzieuk1 said:

P.S is it too early for Gin?!

It’s 5 o’clock somewhere

Make these up on site and chillax. 3 bits of EPS won’t ruin the week. 
 

Just shutter them well externally, belt & braces, and put some extra pins in to keep bits from floating up / away durning the pour.

 

Using a quality expanding foam to bond these together will make them act as 1 solid piece btw; apply pressure for 1hr until cured, and then you’ll have to break the EPS to get these apart again. Rock solid once foamed together and as bombproof as you’ll ever need. 

 

[lizzieuk1]

Thanks all for your support/advice.

Agreed, we will make them up ourselves. Have had to upgrade the xps400 to a 500 version as appears the 400 is elusive. 

We shall prevail! 

 

[IanR]

34 minutes ago, JohnMo said:

But only the steelwork and concrete are structural - the insulation is just that, insulation. It does provide support to the wet concrete while it cures so is just form work that remains in place. It an insulated slab at the end of the day.

It's an Insulated Raft Foundation. The Insulation is structural, 100% of the building's loads are passed through it and spread on to the ground beneath.

[Nickfromwales]

3 minutes ago, IanR said:

It's an Insulated Raft Foundation. The Insulation is structural, 100% of the building's loads are passed through it and spread on to the ground beneath.

Indeed!!

[JohnMo]

2 hours ago, IanR said:

It's an Insulated Raft Foundation. The Insulation is structural, 100% of the building's loads are passed through it and spread on to the ground beneath.

Well corrected😸

[lizzieuk1]

22 hours ago, IanR said:

AFT used to use Springvale EPS, in the UK for their UK orders. I hadn't realised they'd changed to their Swedish Supplier for the UK orders. I did get extras from Springvale, but needed Olaf to "OK" the order. I assume the AFT <-> Springvale relationship turned sour???

Have you got Olaf's details? He still has the AFT domain, so his email is likely still operating. I believe I have his UK mobile, but he did use it in when in Sweden - have you got that?

If you are not in a rush, I'd try Olaf to supply the correct sections - no question on insurance cover then.

If not then I'd make them up myself, but you need to use the EPS200 or EPS300 spec that L Formers were specified in.

Thanks Ian,

I'm not sure about the Springvale deal, our upstands appear to be xps on the base with an eps upstand. Looks as though Springvale only use eps (as do FutureFound/Buildlite) so I'm not sure if that would be an issue - assume if the strength is equivalent it shouldn't be.  I will call them though.

I've tried to contact Olaf on his mobile but its not accepting calls. Not tried email yet but will do that. 

We can source the xps base material easily but the eps is an issue, we need a 90mm but appears it's in 80 or 100 and the kpa rating also difficult - I think we need 100 but not 100% on that, it may be 200!  Again, proving hard to source.

Currently looking at parapet upstand boards, can get those in 86mm or 106mm 300kpa xps but either a bit big or a bit small, not ideal but may do the job. 

Nothing simple as a solution thus far 😬

[IanR]

55 minutes ago, lizzieuk1 said:

Thanks Ian,

I'm not sure about the Springvale deal, our upstands appear to be xps on the base with an eps upstand. Looks as though Springvale only use eps (as do FutureFound/Buildlite) so I'm not sure if that would be an issue - assume if the strength is equivalent it shouldn't be.  I will call them though.

I've tried to contact Olaf on his mobile but its not accepting calls. Not tried email yet but will do that. 

We can source the xps base material easily but the eps is an issue, we need a 90mm but appears it's in 80 or 100 and the kpa rating also difficult - I think we need 100 but not 100% on that, it may be 200!  Again, proving hard to source.

Currently looking at parapet upstand boards, can get those in 86mm or 106mm 300kpa xps but either a bit big or a bit small, not ideal but may do the job. 

Nothing simple as a solution thus far 😬

I ended up with some left over, but believe they are EPS200. If the form is correct I can check the spec. I had two different profiles:

 

and

 

 

The two different profiles were used on mine to create and integral ring beam, and then a seperate outer ring beam.

If either appear to be a similar shape to what you need, let me know the dimensions and I will check and confirm the EPS Spec.

[Redbeard]

1 hour ago, lizzieuk1 said:

We can source the xps base material easily but the eps is an issue, we need a 90mm

Like you, I have no idea about the different grades, but I have bought 90mm Graphite EPS from EWI store (www.ewistore.co.uk) and they are still listing it. This was, as you might guess, for EWI, not for a footing. They will almost certainly know where, if anywhere, you can get the grade you need.

[SteamyTea]

2 hours ago, lizzieuk1 said:

so I'm not sure if that would be an issue

If I remember correctly, XPS retains less water and is used for areas that may get damp, so are used for foundations. The Building Regs has a bit about it.

[Square Feet]

On 23/09/2026 at 11:42, IanR said:

Interesting... Are you doing the calcs, or a 3rd party SE, and does their insurance cover you for the DIY approach? I couldn't find a way of avoiding being "locked in" to a specific supplier and being charged a premium for the EPS - although I was happy in the end (after a long search and negotiation) the premium wasn't too high.

I am meeting Gus Potter of this parish (SE) on Monday and that will be amongst the topics of conversation.

[Gus Potter]

On 23/09/2026 at 09:43, lizzieuk1 said:

Oh lord, I could cry. 

Sorry its long but please read!

Don't cry and don’t apologise for a long read, you want to see what some of myself and others write when we get keen! 

 

As a bit of background I also design rafts, ground bearing slabs and everything in between. I share some of the stuff I do on BH, but also want to see what my competitors are up to. I've had a look at AFT's design details and I can see that they know their stuff, some of their designs are very elegant. Olaf is mentioned. He strikes me as being a very knowledgeable Engineer with excellent creative skills based on first principle design. 

 

If you are short on your modules then you can improvise. 

 

There are a few key steps to this. 

 

1. When you improvise you have to be very careful you don't change the load path down through the insulation for example. The diagram below is probably more complex than yours. The hatch below the slab shows XPS insulation, the bit up the sides is PIR insulation. The key bit is that I'm stepping the XPS so the load transfer from the concrete goes down to the hardcore below in direct bearing at 45 degrees. The extra rebar you see and the square links are due to the fact that this raft is supporting point loads from an oak frame, and the raft rests on some engineered fill I've designed. The external plinth course, only extends some 5 - 6 courses above ground level and is deliberately decoupled from the main structural frame, partly for thermal performance for example. 

 

 

Now if you can get your head round this then you are well on you way to being able to sort the problem yourself. 

 

2/ Next is to understand what insulation you could use to improvise. You want to get this off the shelf. Insulation is primarily specified with a certain compressive strength at 10% compression. EPS is very squashy, even though it seems initially it has the same strength as other insulations.  If it squashes too much before carrying the load then it will compromise the structure, too much deflection for example, which will crack your concrete. Don't get caught out, check to see the insulation you use to fix this is not more squashy than AFD insulation specified. 

 

On 23/09/2026 at 09:43, lizzieuk1 said:

No idea what else, all suggestions gratefully received!

Post the AFD detail you have and let us all have a look. My gut feeling is that there is a simple and justifiable fix available to you without any drama. 

 

Keep your head up!