My Garden Room Build - 9m x 4m

[Molynoox]

If you read it all you deserve a medal
I used 90mm nails for framing using my hikoki.
I hand nailed the cladding nails, couldn't justify the cost of another nail gun. I bought stainless steel, 50mm nails for that, as recommended by Silva timber. Also face fixed the nails, not secret nailing. Silva recommends face fix also, as do all the cladding companies it seems. I think I tried secret nailing and it just wasn't working. Maybe need a nail gun for that one, and smaller nails. Not sure.

I am wondering if I could have used my hikoki for the cladding....

 

[Molynoox]

Interesting to read that you are switching from SIPS. I am going to be doing another build and I am currently investigating SIPS as the method!

I haven't done the accurate costings yet but my rough estimates are that it is more expensive on materials. But cheaper on time as it goes up faster.

I don't want to complicate your decision making but there is a sort of in between option you might want to consider, I am looking into this, which is buying SIPS panels and cutting them to size yourself.

I think a lot of the cost in SIPS could be the custom design process for the panel layout that is required.

Are you looking at a custom SIPS design or an off the shelf SIPS garden room?

Martin

 

[BucksDad]

It is a custom design which I did and where I specified a number of full panels + the height / widths of cuts in each panel.. no design fee per say however there is a cutting charge of £25 + VAT per panel.

The things I've found are
- Each connection between the panels is 50mm, so to make the timber spline, you're connecting two lots of 50mm timber together - every 1220mm. This is effectively the same as a timber frame with 600mm centres, so even going down to 400mm centres, the cost is not that different in terms of timber. I'd argue the time to construct these and then put them in, including nailing, squirting foam etc. is probably comparable to building out a timber frame - albeit there is then no time then needed for the insulation / OSB.
- The panels are heavy. I don't fancy trying to lift the panels by myself and timber frame gives you the option of a lot of solo work.
- In a SIPS panel, you are paying for insulation + 2 sides of OSB and you still need an internal finish (in my case plywood). Therefore when I compare the cost, with a SIPS panel, I am paying for 2 sides of OSB, insulation + plywood. For timber frame construction, I don't need either layer of OSB - my walls will be as per Mike's shed method - cladding, batten, breather membrane, frame, vapour barrier, plywood, so I am effectively paying for insulation + plywood, removing the cost of OSB
- Constructing timber frame, you can order from a local timber yard and pay minimal delivery (I have a local one 10 mins drive from me who I think charge £20!). For 15 SIPs panels, the delivery charge I was quoted was £350+VAT (£420)
- I wouldn't fancy trying to cut the panels and make the rebates myself, it looks a real pig of a job.

Anyway, the long and short of it is that the quote for the SIPs panels, required timber, cuts and delivery was £3150. I have costed up the timber frame construction and it comes to £1300. For that SIPs cost, I am paying for 30 sheets of OSB I don't need and there is £300 for the cutting and £420 for the delivery.

Although overall construction time will be quicker with SIPs and a bit more thermally efficient, unfortunately I can't justify that price difference - that's a lot of tools I can buy instead

If you planned to do a double skin of OSB anyway, then the cost difference does reduce a lot and probably makes it more attractive.

 

[Molynoox]

It is a custom design which I did and where I specified a number of full panels + the height / widths of cuts in each panel.. no design fee per say however there is a cutting charge of £25 + VAT per panel.

The things I've found are
- Each connection between the panels is 50mm, so to make the timber spline, you're connecting two lots of 50mm timber together - every 1220mm. This is effectively the same as a timber frame with 600mm centres, so even going down to 400mm centres, the cost is not that different in terms of timber. I'd argue the time to construct these and then put them in, including nailing, squirting foam etc. is probably comparable to building out a timber frame - albeit there is then no time then needed for the insulation / OSB.
- The panels are heavy. I don't fancy trying to lift the panels by myself and timber frame gives you the option of a lot of solo work.
- In a SIPS panel, you are paying for insulation + 2 sides of OSB and you still need an internal finish (in my case plywood). Therefore when I compare the cost, with a SIPS panel, I am paying for 2 sides of OSB, insulation + plywood. For timber frame construction, I don't need either layer of OSB - my walls will be as per Mike's shed method - cladding, batten, breather membrane, frame, vapour barrier, plywood, so I am effectively paying for insulation + plywood, removing the cost of OSB
- Constructing timber frame, you can order from a local timber yard and pay minimal delivery (I have a local one 10 mins drive from me who I think charge £20!). For 15 SIPs panels, the delivery charge I was quoted was £350+VAT (£420)
- I wouldn't fancy trying to cut the panels and make the rebates myself, it looks a real pig of a job.

Anyway, the long and short of it is that the quote for the SIPs panels, required timber, cuts and delivery was £3150. I have costed up the timber frame construction and it comes to £1300. For that SIPs cost, I am paying for 30 sheets of OSB I don't need and there is £300 for the cutting and £420 for the delivery.

Although overall construction time will be quicker with SIPs and a bit more thermally efficient, unfortunately I can't justify that price difference - that's a lot of tools I can buy instead

If you planned to do a double skin of OSB anyway, then the cost difference does reduce a lot and probably makes it more attractive.

Lovely summary
Lots of great food for thought in that post. As I am investigating SIPS at the moment this information is excellent timing for me.

On the splines, some of the systems don't use timbers to connect, they use instead a sort of mini SIP panel. I wonder if those are cheaper than a timber spline, and also quicker to fit than two timbers back to back?

One aspect that I'm currently investigating about SIPS is electrical first fix, I think this could offer an advantage over timber framing because you don't need to drill through any timbers to get the cable runs, could be an efficiency gain. Also other things like the OSB on interior surface, underneath plasterboard could be handy for hanging heaters, TV etc.

Just thoughts at this stage as I'm just starting my journey learning about these but I think there could be done nice efficiencies with SIPS when considering the full package. And also some downsides of course.

I am going to end up with a sort of comparison matrix between timber framing and SIPS when I'm done looking at this. I wonder if it would be worth me posting that here or doing a separate thread about it even.... Yet more knowledge that seems wasted on one person / one build

Martin

 

[HOJ]

you don't need to drill through any timbers to get the cable runs

We don't.

In a "residential" construction, same as with a stick build , when using SIPS you would/should create an internal service void for electrics/plumbing, on the inboard side of a vapour membrane.

 

[Molynoox]

We don't.

In a "residential" construction, same as with a stick build , when using SIPS you would/should create an internal service void for electrics/plumbing, on the inboard side of a vapour membrane.

Yup. I've got that far in my research, I think this is quite a tidy solution. You can simply put up two battens per vertical so you create a gap for the cable runs through the middle of both battens.

One thing that I was curious about is the strength of the joint between batten and SIPS panel, particularly on the ceiling, with plasterboard hanging off it. Presumably screwing into the OSB on face of SIP is strong enough? What screws are used are they specialist ones?

Martin

 

[HOJ]

You can simply put up two battens per vertical so you create a gap for the cable runs through the middle of both battens.

We set ours at 600mm centers for the plasterboard gauge, unless we need something specific, but also block round any switch/socket outlets that are in isolation.

Presumably screwing into the OSB on face of SIP is strong enough? What screws are used are they specialist ones?

1st fix Ring nails, @ 300mm spacing, length to suit batten thickness + 25mm (typically 50mm) or good quality screws, were its awkward to get to.

This is one I'm "helping" out on, this is awkward to do..

 

[Molynoox]

why do you need block around sockets? and by that do you mean create a ring of batten behind the PB, around the perimeter of socket?

 

[Molynoox]

I wonder what the pull out force is on a 50mm ring shank nail when it's going into only 12mm of OSB?
It doesn't feel like it would be strong enough to support plasterboards on a ceiling - I was worried about screws not being good enough but you are saying that ring shank nails are ok!

 

[HOJ]

create a ring of batten behind the PB, around the perimeter of socket?

Precisely, a lot of spark's prefer to use metal back boxes rather than the plaster board plastic ones, so we end up fitting pieces of batten round the perimeter of the boxes to stop the face plates pulling the plasterboard back , the better option would be to get the beggars for the money they charge, to pack the box out or use a deeper box in the first place, its a problem with attitude, happens all the time , trades don't think about the follow on.

pull out force is on a 50mm ring shank nail when it's going into only 12mm of OSB?

The nails aren't working in isolation, you could look at how a screw could hold up plaster board in the same way, we consider the circumstance and fix accordingly (be it more nails, screws, glue if appropriate)

 

[Molynoox]

Precisely, a lot of spark's prefer to use metal back boxes rather than the plaster board plastic ones, so we end up fitting pieces of batten round the perimeter of the boxes to stop the face plates pulling the plasterboard back , the better option would be to get the beggars for the money they charge, to pack the box out or use a deeper box in the first place, its a problem with attitude, happens all the time , trades don't think about the follow on.


The nails aren't working in isolation, you could look at how a screw could hold up plaster board in the same way, we consider the circumstance and fix accordingly (be it more nails, screws, glue if appropriate)

Ok thanks.
Sorry for more questions, just curious, but do you excavate a rebate into the sips panel for the electrical back boxes? I can't imagine 25mm is enough for the back box.

When you say the nail isn't working in isolation... it is in my head! The nail goes through batten and into the sip panel in the ceiling. The PB is fastened to the batten. Therefore the nails are the only thing holding up the PB to the SIP. Or do your plasterboard screws go into OSB also?

Martin

 

[HOJ]

excavate a rebate into the sips panel for the electrical back boxes?

You can't dig a hole in the SIPS without compromising its integrity and that of the vapour membrane. Be better if the sparks used 35mm deep boxes it wouldn't be an issue, it would end up be fairly flush to the PB front face, (25mm batten + 12.5 PB) my problem is I get in to the job after they've 1st fixed, and have to work round, using the principal of the 7P's would be good! on a lot of projects I go to.

When you say the nail isn't working in isolation... it is in my head!

You keep saying "the nail" we use thousands on a job, (I buy boxes of 2500 in a box) what I mean in isolation, is, 1 nail & I can pull it out, not easily though, 10 and I'm in for a major battle, over shoot on PB screw length also adds to fixing, but not relied upon.

I didn't mean to hijack you excellent thread, its only since SIPS has come up, maybe wait till you've done your "comparison matrix between timber framing and SIPS", we could pick up again

SIPS is more expensive than stick, but 55% quicker to build, the one I'm "helping" out on, took 2 weeks to water tight ish!

Paul

 

[Molynoox]

You can't dig a hole in the SIPS without compromising its integrity and that of the vapour membrane. Be better if the sparks used 35mm deep boxes it wouldn't be an issue, it would end up be fairly flush to the PB front face, (25mm batten + 12.5 PB) my problem is I get in to the job after they've 1st fixed, and have to work round, using the principal of the 7P's would be good! on a lot of projects I go to.


You keep saying "the nail" we use thousands on a job, (I buy boxes of 2500 in a box) what I mean in isolation, is, 1 nail & I can pull it out, not easily though, 10 and I'm in for a major battle, over shoot on PB screw length also adds to fixing, but not relied upon.

I didn't mean to hijack you excellent thread, its only since SIPS has come up, maybe wait till you've done your "comparison matrix between timber framing and SIPS", we could pick up again

SIPS is more expensive than stick, but 55% quicker to build, the one I'm "helping" out on, took 2 weeks to water tight ish!

Paul

Yes you are right we are getting off topic, and it's my fault, but I'm so keen to pick your brains
I am definitely going to start a fresh thread on this so it would be good to get your views in there.

Oh yeah, regarding the nails I know there is more than one, I'm just not explaining myself well, but I understand your point now anyway im still surprised though

I like your last paragraph, that's exactly where I am with my thinking at the moment... time is money, and I think I am starting to understand the popularity of sips now.

Martin

 

[Scruples]

Lovely summary
Lots of great food for thought in that post. As I am investigating SIPS at the moment this information is excellent timing for me.

On the splines, some of the systems don't use timbers to connect, they use instead a sort of mini SIP panel. I wonder if those are cheaper than a timber spline, and also quicker to fit than two timbers back to back?

One aspect that I'm currently investigating about SIPS is electrical first fix, I think this could offer an advantage over timber framing because you don't need to drill through any timbers to get the cable runs, could be an efficiency gain. Also other things like the OSB on interior surface, underneath plasterboard could be handy for hanging heaters, TV etc.

Just thoughts at this stage as I'm just starting my journey learning about these but I think there could be done nice efficiencies with SIPS when considering the full package. And also some downsides of course.

I am going to end up with a sort of comparison matrix between timber framing and SIPS when I'm done looking at this. I wonder if it would be worth me posting that here or doing a separate thread about it even.... Yet more knowledge that seems wasted on one person / one build

Martin

When I built my workshop, I considered the different methods of wiring it and ended up using 100mm plastic trunking around the whole inside of building. I've never regretted it. It's easy to add/move sockets giving me a flexibility that I wouldn't have had by recessed cabling. I used a segregated trunking as I wanted to run some ethernet cables.

 

[BucksDad]

Indeed @Scruples, I'm doing the same but @Molynoox is building garden rooms so won't be wanting his utilities surface mounted.

@Molynoox I would start a separate thread for the SIPs discussion.

 

[BucksDad]

@Molynoox Do you notice the fixings on your fascias on the garden room? When I see pictures or videos on YT, they look really obvious and spoil the look somewhat, wouldn't mind a fixture-free fascia.. do you notice it day to day?

 

[Molynoox]

Hi

@Molynoox Do you notice the fixings on your fascias on the garden room? When I see pictures or videos on YT, they look really obvious and spoil the look somewhat, wouldn't mind a fixture-free fascia.. do you notice it day to day?

Yes it's my one annoyance with the build. Ive always hated those little bullets sticking out of the front of the fascias. I spent a bit of time looking for an alternative when I was building mine but didn't find anything in time for when I needed it.

I really wanted powder coated aluminium or something like that, a nice clean finish. I've seen it on some builds but it's quite rare. I couldn't find any suppliers for it at the time and i sort of gave up.

The aluminium trim is quite popular with some of the sips builders if they are using those Kingspan roof panels, and it looks good from the front but not from the top IMO. So I would still want to use EPDM (and not Kingspan panel) but with Alu trim instead the plastic ones.

You will see on my build that I managed to have just one set of visible bullets by hiding the fascia fixings (using normal nails) under the roof trim fixings (the roof trim fixings are those plastic capped nails that you can see).

So I am keen to find a solution for that one. It would probably need to be a roof trim underneath to direct water off the EPDM roof, and the alu trims on top. The roof trims are not as deep as the roof thickness therefore it would probably require an additional board to act as a packer sitting below the roof trim. With the roof trim and packer board side by side (or top to bottom I suppose) this would give a flat surface for the alu trim to mate up to on the fascia.

Martin

 

[BucksDad]

I was wondering about doing a double fascia... do the roof trim and fascia as per normal, then put another fascia on top which is taller and hides the roof trim. Glue some bits of wood every 400mm to the fascia with CT1 and then use buttonfix with the wood spacers to give a fixture-free external fascia

 

[Molynoox]

I was wondering about doing a double fascia... do the roof trim and fascia as per normal, then put another fascia on top which is taller and hides the roof trim. Glue some bits of wood every 400mm to the fascia with CT1 and then use buttonfix with the wood spacers to give a fixture-free external fascia

that's a brilliant idea.
I think you could miss out the first fascia board too, and then its the exact same materials as a conventional build other than the extra wooden packers and the buttons. I'm going to model that up to get my head around it.
Martin

 

[BucksDad]

My only concern with skipping the first fascia board is you will have a small gap that rain can fall through and potentially get the exposed wood wet