SIPs quote

[Kevan Marshall]

Just had a quote for supply and erection of SIPs house, my house is 180sqm ground floor area with provision to convert loft 70sqm at later date, external walls 197mm SIP panels to give U value of 0.13 or 172mm SIP panels plus 25mm PIR internal insulation to give U value of 0.12, roof is of vaulted truss system with steels in to support and boarded out and insulated to 0.12, all supporting stud walls are supplied, posi joists are supplied for loft conversion and floor boarded out, all wall and roof locations made airtight and battened out for service void ready to plasterboard, all exterior areas made weather tight, all crane hire, delivery costs included, airtight test done after I fit windows, all paperwork done for building control, with quite a lot of structural support walls going in leaves me very few stud walls to put in after installation of screed floor, I am waiting on quotes from two other SIPs companies but does this seem a reasonable price at 100k?

 

kind regards,

Kevan.

[Russell griffiths]

What score do they say they will achieve with the airtightness test. 

[Nickfromwales]

18 hours ago, Kevan Marshall said:

Just had a quote for supply and erection of SIPs house, my house is 180sqm ground floor area with provision to convert loft 70sqm at later date, external walls 197mm SIP panels to give U value of 0.13 or 172mm SIP panels plus 25mm PIR internal insulation to give U value of 0.12, roof is of vaulted truss system with steels in to support and boarded out and insulated to 0.12, all supporting stud walls are supplied, posi joists are supplied for loft conversion and floor boarded out, all wall and roof locations made airtight and battened out for service void ready to plasterboard, all exterior areas made weather tight, all crane hire, delivery costs included, airtight test done after I fit windows, all paperwork done for building control, with quite a lot of structural support walls going in leaves me very few stud walls to put in after installation of screed floor, I am waiting on quotes from two other SIPs companies but does this seem a reasonable price at 100k?

 

kind regards,

Kevan.

Doesn’t sound terrible tbh, but I’m just not a fan of SIP’s vs a proper timber frame blown full of cellulose.

 

Have you read the small print twenty times? Usually you’ll be responsible for a lot of stuff and you need that costed out before you take one more step forward, so you have a high level project cost.

 

I was going to ask about the promised AT score, but I’m assuming 1.0ach or close to? 

[Kevan Marshall]

15 hours ago, Russell griffiths said:

What score do they say they will achieve with the airtightness test. 

They have told me AT shall be well within limits, as long as I install good quality triple glazing then it should be up into passive standard 

[Kevan Marshall]

3 hours ago, Nickfromwales said:

Doesn’t sound terrible tbh, but I’m just not a fan of SIP’s vs a proper timber frame blown full of cellulose.

 

Have you read the small print twenty times? Usually you’ll be responsible for a lot of stuff and you need that costed out before you take one more step forward, so you have a high level project cost.

 

I was going to ask about the promised AT score, but I’m assuming 1.0ach or close to? 

Yes, even on the quote they are 100% clear what they are responsible for and what I am responsible for, only thing I want to ensure is that window sizes as per drawing are within tolerance and if windows do not fit due to incorrect sizes then they shall be responsible, they assure me they have never had any issues before and windows/doors can be ordered during  kit manufacture 

kind regards,

Kevan.

[JohnMo]

8 hours ago, Kevan Marshall said:

only thing I want to ensure is that window sizes as per drawing are within tolerance

That is pretty easy for most builds. One caveat, you and everyone else are working to the same drawing revision. People change stuff, they assume because they know, and the architect knows, everyone does.

 

I had final sign off on all drawings for the build, once our building warrant was approved, no drawings got changed, no details where changed. But that isn't the case very often. So dot you eyes and cross you tees.

[Mr Punter]

16 minutes ago, JohnMo said:

That is pretty easy for most builds. One caveat, you and everyone else are working to the same drawing revision. People change stuff, they assume because they know, and the architect knows, everyone does.

 

I had final sign off on all drawings for the build, once our building warrant was approved, no drawings got changed, no details where changed. But that isn't the case very often. So dot you eyes and cross you tees.

 

+1

I changed a couple of door handings and although drawings were updated, the electricians worked from an old set of drawings we had sent out for quote purposes, so there was some messing to get light switches in the right place.

[Kevan Marshall]

1 hour ago, JohnMo said:

That is pretty easy for most builds. One caveat, you and everyone else are working to the same drawing revision. People change stuff, they assume because they know, and the architect knows, everyone does.

 

I had final sign off on all drawings for the build, once our building warrant was approved, no drawings got changed, no details where changed. But that isn't the case very often. So dot you eyes and cross you tees.

Thanks John,

I want to be strict on no changes, to be honest I have more confidence in my contractors than I do my Architect who is questioning everything, trying to change things and complicate everything, unfortunately I need him for getting everything signed off.

 

kind regards,

Kevan.

[Kevan Marshall]

1 hour ago, Mr Punter said:

 

+1

I changed a couple of door handings and although drawings were updated, the electricians worked from an old set of drawings we had sent out for quote purposes, so there was some messing to get light switches in the right place.

I spent a lot of my time looking at every detail as I had the attitude that if you change anything it costs money, I have also told the boss (wife) that, also went down the KISS route (keep it simple and stupid).

[SteamyTea]

18 hours ago, Kevan Marshall said:

They have told me AT shall be well within limits

Do they mean Building Regulation limits, which are pretty poor.

 

[Kevan Marshall]

2 hours ago, SteamyTea said:

Do they mean Building Regulation limits, which are pretty poor.

 

Well beyond that getting upto passive house standards 

[JohnMo]

13 hours ago, Kevan Marshall said:

Well beyond that getting upto passive house standards 

I would want a number, otherwise it's meaningless. Getting towards something is very open to interpretation, scoring 6m³/m² @ 50Pa is getting towards passivhaus (it's nowhere near) compared 10. You possibly thinking under 1.0, so there may or may not be a big gap of expectations?

[ProDave]

On 19/12/2025 at 23:52, Kevan Marshall said:

only thing I want to ensure is that window sizes as per drawing are within tolerance and if windows do not fit due to incorrect sizes then they shall be responsible

Regardless of any assurance, before ordering windows I would MEASURE the actual window openings as built.

 

I paid a local builder company to build and erect my frame, and then later paid them to supply and fit windows.  Even they did not trust they had built the openings to the drawing, and measured them before ordering windows.

[saveasteading]

46 minutes ago, ProDave said:

openings to the drawing,

A quality window contractor will minimise the gap, and the amount of filler/ foam needed to fill it. Even the best builder will have wobbles and variations in the opening, and that quality window contractor will insist on measuring. They will also use expanding tape to get a good closure that will move with the building , not squirt stuff in after.

[Kevan Marshall]

5 hours ago, JohnMo said:

I would want a number, otherwise it's meaningless. Getting towards something is very open to interpretation, scoring 6m³/m² @ 50Pa is getting towards passivhaus (it's nowhere near) compared 10. You possibly thinking under 1.0, so there may or may not be a big gap of expectations?

Hi John,

I shall ask the TF company what they can guarantee and ask for proof from previous builds

[Kevan Marshall]

3 hours ago, saveasteading said:

A quality window contractor will minimise the gap, and the amount of filler/ foam needed to fill it. Even the best builder will have wobbles and variations in the opening, and that quality window contractor will insist on measuring. They will also use expanding tape to get a good closure that will move with the building , not squirt stuff in after.

As soon as I get detailed drawings from TF company I’ll ask Window suppliers what their turn around shall be, if they install the walls it may take the TF company one week to install the roof, etc so that might help me for time

[Kevan Marshall]

4 hours ago, ProDave said:

Regardless of any assurance, before ordering windows I would MEASURE the actual window openings as built.

 

I paid a local builder company to build and erect my frame, and then later paid them to supply and fit windows.  Even they did not trust they had built the openings to the drawing, and measured them before ordering windows.

As soon as I get detailed drawings from TF company I’ll ask Window suppliers what their turn around shall be, if they install the walls it may take the TF company one week to install the roof, etc so that might help me for time

[Redbeard]

Add a good margin for error to the cited turn-round time. My last big-ish order was estimated at 8 weeks and took just under 14.

[Gus Potter]

On 19/12/2025 at 01:53, Kevan Marshall said:

Just had a quote for supply and erection of SIPs house, my house

 

On 20/12/2025 at 08:46, JohnMo said:

That is pretty easy for most builds. One caveat, you and everyone else are working to the same drawing revision. People change stuff, they assume because they know, and the architect knows, everyone does.

 

I had final sign off on all drawings for the build, once our building warrant was approved, no drawings got changed, no details where changed. But that isn't the case very often. So dot you eyes and cross you tees.

John is right. Once the SIPS are fabricated there is no turning back without potential big cost. 

 

In my experience of self builds the design does get changed more often than not. It is often a small thing, an unforseen event. 

 

.That said, if you have really been this through this and looked at the savings / vs change risk then ok. But you have to have every service position  thought out, boiler flue.. everything, a detailed an dimensioned foundation design and so on. There is no margin for error on SIPS. 

 

SIPS work say on the Athletes Village in Glasgow where they had a few house types but built many. I have have Clients that want to adapt and they are a nightmare. The designer could afford to go into every last detail as there was economy of scale.

 

On a self build to get this to work you need to pay your designer enough to ensure every last bit fits together,  is regs compliant and both of you need to work together very closely. I suspect you have not done this. Paid them enough? 

On 20/12/2025 at 10:19, Kevan Marshall said:

than I do my Architect who is questioning everything

Get to the bottom of this. Your Architect may be a little unsure, they may be nervious as lack experience. It's not a bad thing, everyone needs to learn and work together. You may be a bit of a "scary client" and to your own detriment you may be forcing the design when actually you should not. This is business and if I get a Client that just wants to "pay me from the neck down" I'll warn them of the risks, usually twice... what comes after is for another day.

 

12 hours ago, ProDave said:

Regardless of any assurance, before ordering windows I would MEASURE the actual window openings as built.

This is some of the best advice you will ever get! Also check you window order, opening direction is a common mistake, hard to believe but it happens on a regular occurance.

 

 

[Kevan Marshall]

2 minutes ago, Gus Potter said:

 

John is right. Once the SIPS are fabricated there is no turning back without potential big cost. 

 

In my experience of self builds the design does get changed more often than not. It is often a small thing, an unforseen event. 

 

.That said, if you have really been this through this and looked at the savings / vs change risk then ok. But you have to have every service position  thought out, boiler flue.. everything, a detailed an dimensioned foundation design and so on. There is no margin for error on SIPS. 

 

SIPS work say on the Athletes Village in Glasgow where they had a few house types but built many. I have have Clients that want to adapt and they are a nightmare. The designer could afford to go into every last detail as there was economy of scale.

 

On a self build to get this to work you need to pay your designer enough to ensure every last bit fits together,  is regs compliant and both of you need to work together very closely. I suspect you have not done this. Paid them enough? 

Get to the bottom of this. Your Architect may be a little unsure, they may be nervious as lack experience. It's not a bad thing, everyone needs to learn and work together. You may be a bit of a "scary client" and to your own detriment you may be forcing the design when actually you should not. This is business and if I get a Client that just wants to "pay me from the neck down" I'll warn them of the risks, usually twice... what comes after is for another day.

 

This is some of the best advice you will ever get! Also check you window order, opening direction is a common mistake, hard to believe but it happens on a regular occurance.

 

 

Thank you Gus,

All good advice, I have spent 9 months researching this whilst waiting on planning and I have to tell my architect how the SIP’s/TF contractor shall do things, My friend who is doing all the civils is an experienced builder who has been dealing with building control for many years so I am confident that everything shall go smoothly, my plans are set in stone and only issue I have had was the Architect changing things to how he wanted, I designed the house at the start and told him if anything needed tweaked a little for the better to do it, unfortunately he completely changed door positions, started adding fitted wardrobes etc, in rooms that we planned to put our own furniture in, it taken six drafts to get things right and they ended up near enough to my original layout, I shall speak to my TF supplier to as about windows as they assure me they have never had any issues, TF company shall send foundation drawing details for my builder and I shall ensure all soil pipes are in a good location, I am waiting for two more quotes coming in then hopefully I can start progressing with sorting out prices for windows, MVHR, electrics, plumbing, etc

 

kind regards,

kevan

[Gus Potter]

16 minutes ago, Kevan Marshall said:

My friend who is doing all the civils is an experienced builder who has been dealing with building control for many years so I am confident

The big question is here is your friend going to be doing the work? 

 

A word of caution. Friendships can end quickly if there is a disagreement about money. 

 

I can see you have got all the major design elements in place and put that into work packages.

 

You have to double check all setting out, where the design interfaces stop. I work from time to time as a lead designer / Structural engineer and the problems often arise at the interfaces between the different design packages not marrying up. Some are downright dangerous. 

 

This is where your risk and unforseen costs lie. 

 

Neglect this at your peril. Be blunt and ask each work package provider if what they are doing is going to fit with the next part of the structure. I bet your SIPS supplier has made caveats, DO NOT bury your head in the sand. Provide them with drawings of the interfaces and ask them specifically "IS YOUR DESIGN COMPATIBLE" with the proposed interface and what structral forces need to be transferred. You'll see they caveat stuff. That is fair but you MUST understand what the caveats mean. 

 

 

25 minutes ago, Kevan Marshall said:

friend who is doing all the civils is an experienced builder

The fact that you are on BH suggests to me that while your friend may be experienced they may be missing something. 

 

Diplomacy is going to be required here.