Hello! I've bitten off more than I can.... (SIP Office Room)

[Jamie McNaught]

Hi all,

 

We're out of space... wife and I both now work from home and using kids bedrooms as offices is not working. I'm getting kicked out into the proposed garden office....

 

So, we're tight on space (in the back garden), time and money - I've ruled out:

    brick & block due to thick walls (small back garden), cost (cant afford a bricky) and larger slab/foundations

    timber due to time (and potentially cost)

so we're looking at a self build SIP office. Approx 5.2m x 3.5m.

 

Looking to go the whole hog - 5m bifolds in a steel rsj/ beam goal post, 2m x 1m skylight and bricksips rear wall. Initially wanted to do an oak frame to support the albeit shorter bifolds but had to rule out due to extreme cost and manufacturers reluctance to discuss beam deflection on the oak (but we might clad the rsj in oak).

 

Which is the best forum to ask SIP & foundation questions? 

     House Construction & Structural Issues ->  House Construction ->  Structural Insulated Panels (SIPs) 

or should I be posting to:
     House Construction & Structural Issues -> Landscaping & Outdoor Buildings -> Garages & Workshops

 

Cheers,

 

J

[Ferdinand]

1 hour ago, Jamie McNaught said:

We're out of space... wife and I both now work from home and using kids bedrooms as offices is not working. I'm getting kicked out into the proposed garden office....

 

Welcome.

Sounds like an effective tactic to get it built.

[PeterW]

Bin the bifolds - you will never open them. Go for two pairs of French doors or even a couple of full height panels and a pair of doors in the middle. In the space you have they will intrude into the space, and also make it overheat. 
 

If cost is a real driver then consider one of the log systems such as Tuin and then insulate the inside. It will be much cheaper than SIPs and easier too as it will go on pad foundations.  

[Nickfromwales]

Are you looking to DIY or are you going for SIPS so you can have it made and erected from the comfort of the pub bar? 
I’ve done a 6m x 3.6m timber frame man shed / home office and stick built it with 4x2 walls and 5x2 rafters. Racked internally with OSB3 and same for floor. Uninsulated metal profile roof ( 6.3m long, one piece sections so no joints ) and it was cheap as chips to put up.

Plenty of budget left to have the remaining voids full filled with PIR vs paying for SIPs ( but I’ve not bothered as I’ll just make it draught-proof and live with the occasional running costs of a cheap £200 split ASHP I nabbed off gumtree a while back ) and then you could also fit insulated plasterboard internally to stave off cold bridging through the studs. You could also make the walls 5x2 and the roof 6x2 or even 7x2 to allow for more insulation, if you will spend a lot of winter in there?

Deffo go for the split air-con, as in the summer it will be roasting in there. Mine is nigh on unbearable, so the split will be a lifesaver for me as I’ll be working on stuff as well as ‘at the desk’. 
So lazy boy or DIY? You can save some serious money with DIY. 

Edited October 9, 2020 by Nickfromwales

[daiking]

I was trying to budget something DIY (Not SIPs) as built stuff was as expensive as a house. But still a bi fold was a massive chunk of the budget. Now we had a 3m door put into the house 5 years ago and that was about £3k for the door. I don’t suppose they’ve got much cheaper.

 

What with everything that’s going on, we managed to convert the box room into an office for me so there is no rush but my wife’s current plan is to get something like a Tuin Lory log cabin - £4.5k + other costs. It’s a 45mm thick log which they suggest as minimum for all year occupation but even thicker is better. As I won’t be working in it, we’ll be fine with heating it occasionally. I wouldn’t want to get a log cabin and then insulate it internally IYSWIM.

[Temp]

Possible insulated roof panels..

 

https://www.panelsell.co.uk/insulated-roof-panels?source=google&medium=adwords&campaign=1614494041&adgroup=62109888958&keyword=insulated roof panels&matchtype=e&adposition=&device=t&network=g&gclid=CjwKCAjwlID8BRAFEiwAnUoK1bB9upYPK1cPN1_smpBo1Oyz_koIJikm6xUO6Dz63dWeO66Hd_rhWRoC--cQAvD_BwE

 

Add more insulation below.

[Nick1c]

A second vote for Tuin, with a couple of caveats. They come with no base, which adds a fair bit to the overall cost. We got a Leipzig & put 50mm cellotex on the floor & roof which helps make it more comfortable (it is used as a garden shed/store/workshop). They move an unbelievable amount over the seasons, any rigid links between boards may well result in twisting/deformation so fitting it out needs careful thought. 

[daiking]

56 minutes ago, Nick1c said:

A second vote for Tuin, with a couple of caveats. They come with no base, which adds a fair bit to the overall cost. We got a Leipzig & put 50mm cellotex on the floor & roof which helps make it more comfortable (it is used as a garden shed/store/workshop). They move an unbelievable amount over the seasons, any rigid links between boards may well result in twisting/deformation so fitting it out needs careful thought. 

Should have said, would still insulate roof and floor as they advise but you Can do this without losing the log cabin look.

[Jamie McNaught]

23 hours ago, Ferdinand said:

 

Welcome.

Sounds like an effective tactic to get it built.

Yeah... I am due to get kicked out into it shortly 'come what may'... it's absence from the garden doesn't seem to be a blocker to this eviction.

 

21 hours ago, PeterW said:

Bin the bifolds - you will never open them. Go for two pairs of French doors or even a couple of full height panels and a pair of doors in the middle. In the space you have they will intrude into the space, and also make it overheat. 
 

If cost is a real driver then consider one of the log systems such as Tuin and then insulate the inside. It will be much cheaper than SIPs and easier too as it will go on pad foundations.  

The bifolds are intended to open outwards - 550 config so one 'access' door which can just be opened. We want the outside space to 'come into the inside space' / be able to use it all like one space for parties etc.

 

Tuin log cabins do look good... which I has found them sooner as it might have stopped me going down the SIP rabbit hole.

[Jamie McNaught]

12 hours ago, Nickfromwales said:

Are you looking to DIY or are you going for SIPS so you can have it made and erected from the comfort of the pub bar? 
I’ve done a 6m x 3.6m timber frame man shed / home office and stick built it with 4x2 walls and 5x2 rafters. Racked internally with OSB3 and same for floor. Uninsulated metal profile roof ( 6.3m long, one piece sections so no joints ) and it was cheap as chips to put up.

Plenty of budget left to have the remaining voids full filled with PIR vs paying for SIPs ( but I’ve not bothered as I’ll just make it draught-proof and live with the occasional running costs of a cheap £200 split ASHP I nabbed off gumtree a while back ) and then you could also fit insulated plasterboard internally to stave off cold bridging through the studs. You could also make the walls 5x2 and the roof 6x2 or even 7x2 to allow for more insulation, if you will spend a lot of winter in there?

Deffo go for the split air-con, as in the summer it will be roasting in there. Mine is nigh on unbearable, so the split will be a lifesaver for me as I’ll be working on stuff as well as ‘at the desk’. 
So lazy boy or DIY? You can save some serious money with DIY. 

While I'd love to do the pub bar approach, this is likely to be majority DIY due to costs (and because I've not got an architect and builders I speak to want professional plans, not my Sketchup efforts), hence the attaction of SIPs to speed it up.

 

Re SIP's costs, what is your (or others) opinons of companies like SuperSIPs (http://www.supersips.uk.com/structural-insulated-panels-prices.htm). I find it hard to believe I could timber frame much cheaper than their sips... or am I looking at the wrong builders merchants?

 

Insulated plasterboard - good idea - going to post some diagrams to ask about cold bridging shortly. Plan was 100mm walls, 150mm roof, but open to suggestions for thicker.... winter in Cambridge is not exactly 'severe' but I will be spending every day in it sitting stationary at the computer - so don't want to be cold - also want to keep the heat out in summer.

[Jamie McNaught]

12 hours ago, daiking said:

I was trying to budget something DIY (Not SIPs) as built stuff was as expensive as a house. But still a bi fold was a massive chunk of the budget. Now we had a 3m door put into the house 5 years ago and that was about £3k for the door. I don’t suppose they’ve got much cheaper.

What with everything that’s going on, we managed to convert the box room into an office for me so there is no rush but my wife’s current plan is to get something like a Tuin Lory log cabin - £4.5k + other costs. It’s a 45mm thick log which they suggest as minimum for all year occupation but even thicker is better. As I won’t be working in it, we’ll be fine with heating it occasionally. I wouldn’t want to get a log cabin and then insulate it internally IYSWIM.

Cheers for the links. Yes, bifold is expensive - about £3400 for 4.8m 5 door. I'm still on the fence - been also looking at 5m sliding doors... but really want to be able to open the space up to the garden. Tuin Log Cabins look good, but like you say... insulation is a bit of an issue for an all year round one used 5 to 6 days a week... they might be a backup if I can't make the SIP thing fly.

[Jamie McNaught]

11 hours ago, Temp said:

Possible insulated roof panels..

 

https://www.panelsell.co.uk/insulated-roof-panels?source=google&medium=adwords&campaign=1614494041&adgroup=62109888958&keyword=insulated roof panels&matchtype=e&adposition=&device=t&network=g&gclid=CjwKCAjwlID8BRAFEiwAnUoK1bB9upYPK1cPN1_smpBo1Oyz_koIJikm6xUO6Dz63dWeO66Hd_rhWRoC--cQAvD_BwE

 

Add more insulation below.

 

Very useful.... SIP's are great, but at 80+ kg, I am not looking forward to trying to get them up for the roof. Good option this.

 

1 hour ago, daiking said:

Should have said, would still insulate roof and floor as they advise but you Can do this without losing the log cabin look.

 

Yeah... it would seem a shame to insulate the walls and loose the look. Do they do any cabins which had insulation between walls, or is it just thicker logs with the bigger ones?

Edited October 9, 2020 by Jamie McNaught

[Jamie McNaught]

2 hours ago, Nick1c said:

A second vote for Tuin, with a couple of caveats. They come with no base, which adds a fair bit to the overall cost. We got a Leipzig & put 50mm cellotex on the floor & roof which helps make it more comfortable (it is used as a garden shed/store/workshop). They move an unbelievable amount over the seasons, any rigid links between boards may well result in twisting/deformation so fitting it out needs careful thought. 

Why do they move? Is this moisture causing the wood to shrink / expand or something else? I've been concerned about expansion on the planned build - e.g. 5m RSJ.

[Nickfromwales]

12 hours ago, Jamie McNaught said:

Re SIP's costs, what is your (or others) opinons of companies like SuperSIPs (http://www.supersips.uk.com/structural-insulated-panels-prices.htm). I find it hard to believe I could timber frame much cheaper than their sips... or am I looking at the wrong builders merchants?

Can't really argue with those prices, just DIY is where the savings would be, plus if plaster-boarding anyway, buying thinner ( cheaper ) frame material and retro-fitting with insulated PB would ba another way of killing two birds with one stone. However, just buying one increment up on those SIPs prices to achieve the same result and fitting PB to those ( prob over a service counter batten to allow for electrics etc ) seems a more straightforward direction.

 

13 hours ago, Jamie McNaught said:

Insulated plasterboard - good idea - going to post some diagrams to ask about cold bridging shortly. Plan was 100mm walls, 150mm roof, but open to suggestions for thicker.... winter in Cambridge is not exactly 'severe' but I will be spending every day in it sitting stationary at the computer - so don't want to be cold - also want to keep the heat out in summer.

Buy insulation once, reduce heating bills forever   I'd still be and advocate of A/C though, for both heating ( which should be negligible in this type of structure ) but more importantly not to cook to death in the summer ( a surprising amount of nuisance noise comes into my 'office' from just cracking open the moderate sized window ( which I have to shut to hold a business conversation ) so be mindful you may not always be able to keep the sliders open all of the time )), but I don't yet have the acoustic batts in the roof void which may help there too.

 

I ran Cat 6 out there too, 1x for external WiFi AP which I mounted on the external 'office' wall ( so the garden now benefits from a very robust WiFi signal ), 1x for the desktop, and 1x for the network / internet printer.  You could just get a cable from your existing BB router and take it to an external AP ( like a Ruckus heavy traffic unit ) and hook everything up to that. Depends on your dependency, but a hard wired cable from the desktop is way better than wireless. 

[Jamie McNaught]

1 hour ago, Nickfromwales said:

Buy insulation once, reduce heating bills forever   I'd still be and advocate of A/C though, for both heating ( which should be negligible in this type of structure ) but more importantly not to cook to death in the summer ( a surprising amount of nuisance noise comes into my 'office' from just cracking open the moderate sized window ( which I have to shut to hold a business conversation ) so be mindful you may not always be able to keep the sliders open all of the time )), but I don't yet have the acoustic batts in the roof void which may help there too.

 

I ran Cat 6 out there too, 1x for external WiFi AP which I mounted on the external 'office' wall ( so the garden now benefits from a very robust WiFi signal ), 1x for the desktop, and 1x for the network / internet printer.  You could just get a cable from your existing BB router and take it to an external AP ( like a Ruckus heavy traffic unit ) and hook everything up to that. Depends on your dependency, but a hard wired cable from the desktop is way better than wireless. 

Would the level of insulation not help keep the heat out in summer or wil the bifolds ruin that? Our house stays fairly cool as long as we keep windows shut... when I say cool... in 2019 it was 38C outside and 27C indoors.... so 'coolish'

 

Yes, will be Cat6 all the way, don't use wifi if it can be avoided.

 

Do you have any experience of routing cables in the SIP's (to avoid a service void cost + space reduction)? I've seen them doing this for US house builds, but not sure if this creates a trap for condensation. Obviously would need to be well planned and done while errecting with careful thought for corners.

[Nickfromwales]

1 hour ago, Jamie McNaught said:

Do you have any experience of routing cables in the SIP's (to avoid a service void cost + space reduction)? I've seen them doing this for US house builds, but not sure if this creates a trap for condensation. Obviously would need to be well planned and done while errecting with careful thought for corners.

I couldn’t imagine a bigger ballache / logistical

nightmare tbh. You can’t ( shouldn’t ) cut into the SIPS face materiel either as they form racking strength, so any f-ups in the PIR core means abandoning that and surface mounting anyway. ( Also you can’t run cables in insulation without de-rating the breakers or upsizing the cables ( a lot ). ?.

[Ferdinand]

2 hours ago, Jamie McNaught said:

Would the level of insulation not help keep the heat out in summer or wil the bifolds ruin that? Our house stays fairly cool as long as we keep windows shut... when I say cool... in 2019 it was 38C outside and 27C indoors.... so 'coolish'

 

 

The level of insulation helps, but the problem is when it eventually heats up and toasts you the heat stays. This when we think about how long the heat pulse takes to get through - and for that we look at the "decrement delay" number for the material to be suitable. For that the stuff in SIPS, or PIT if you are using it, are not that suitable.

 

In a shed  garden room it is more difficult than in a house as it is smaller space (surface area:volume ration etc), so it all works more quickly. 

 

My house is bricks, mortar, and PIR, and it tends to get uncomfortable for me by mid afternoon in a real heatwave. With a different insulation material and  more of it it may have taken longer, but it is built as a good quality conversion only 10-11 years ago, so I am not about to sort that out.

 

A split aircon is really just the currently cheapest and most flexible elastoplast to manage the issue using the least energy.

Edited October 10, 2020 by Ferdinand

[Ferdinand]

On 09/10/2020 at 08:50, Temp said:

Possible insulated roof panels..

 

https://www.panelsell.co.uk/insulated-roof-panels?source=google&medium=adwords&campaign=1614494041&adgroup=62109888958&keyword=insulated roof panels&matchtype=e&adposition=&device=t&network=g&gclid=CjwKCAjwlID8BRAFEiwAnUoK1bB9upYPK1cPN1_smpBo1Oyz_koIJikm6xUO6Dz63dWeO66Hd_rhWRoC--cQAvD_BwE

 

Add more insulation below.

 

Make sure you know how you will work with these.

 

eg How will you cut the compound foam + alu sheet sandwich without the thin alu folding up at the slot.

 

Used a version of this on an s/s extension back in 2000, and it was a sod.

 

May be doable, just make sure you know how.

Edited October 10, 2020 by Ferdinand

[Nick1c]

The change in humidity is what causes the movement - up to 20mm in about 1.7m! I have a board rack fixed to the shed with slots to allow movement which show it up. I think it is particular to this style of construction as no nails/screws are used in the walls. 

[Jamie McNaught]

On 10/10/2020 at 16:37, Nick1c said:

The change in humidity is what causes the movement - up to 20mm in about 1.7m! I have a board rack fixed to the shed with slots to allow movement which show it up. I think it is particular to this style of construction as no nails/screws are used in the walls. 

That is a lot of movement, but I guess given you wouldn't normally plaster the inside of these its probably not such an issue. To think I am getting concerned about 3mm of expansion on 5m of steel rsj....