We have been building with SIPS for a number of years but find that when potential clients visit finished houses, they always point out that the internal feel of the wall feels hollow. You see, most houses are built here in concrete and block.

The reason for this is that in our market, electrical and plumbing fittings pipes are faced fixed to the internal side of the SIPS panel, we then batten out and plasterboard over it. We cannot use pre drilled SIPS here. Also the norm here is to use plastic conduit and full sized electrical boxes (they wont use the slim ones) as opposed to grey twin and earth cabling, service cavities of up to 40 mm are thus required.

To make the wall feel a little more substantial, we have been lining the battens with 9mm OSB prior to dryling, but this is time consuming and expensive in the long run. So I thought about doing something that replicates the solid feel of a SIPS panel over the hollow feel of timber frame.

The idea I have is to line the internal side of the panel with either 40 mm XPS or 175 kg/m Rockwool batt, chase out the channels for the services, and then fix plasterboard on top with 60mm screws. I am hoping that the rigidity of the board and non compressive quality will allow the plasterboard to pull tight onto the panel, hence avoiding the need for battening. The cost and time of this method seems to be less and will mean that there is not a hollow void behind the wall surface.

In addition, I would think that adding another insulation layer will be beneficial as well as by using rockwool as an option, I should be able to increase fire resistance too.

If anyone has done anything similar or has a view on this I would most appreciate it.

Hi Jazzdude
Could you tell me where you are building these? It would seem that you need to educate your local inspectors to except SIPs and the values that are built into them rather than changing the system to suit them, educate them.

Fergie

We have built over a 100 houses here in SIPS and have no problems with the local inspectors. Electricians and and clients will not use twin core wiring on its own. Its a preference that has come over from conduit in concrete and block walls and it is difficult to get the trades to change. Personally I feel that there are great advantages in pulling cables through conduit for future upgrades and additions.

But that is no the issue here.

again perhaps you could explain where it is being built! I have built SIPs in many countries and have not had issues of drilling chase-ways or using them. I do know how it is hard for some to understand SIPs as well as getting trades on board, but if you are the builder then you set the specs they do it or they go without work, Period. Pulling multi lines is not really an issue in chases or conduits as conduits can be installed in the chases if required.

We build in Cyprus.

Not only are we dealing with wiring, but plumbing feeds, air conditioning piping and communications. In all my years as an Architect I have never had a build where the client does not want to change the electrical installation from the approved drawings. Often they do a complete 180.  Face fixing all services to the inside face of the panel, having the client see it there and approving it, and then covering it up I feel is the most flexible way to work. The panels stay intact and there is no need to start cutting and drilling if they want extra points etc.

In countries where twin core is the norm, I know either chased double boarding or boarding on 12mm battens is often used. Most plumbers here use pipe in pipe fixings where an angle is at least 38mm wide. You cannot get elliptical water pipes here. AC pipes are at least 35mm thick when you finish putting Armaflex on them.

Once again, the issue is not what kind of services we have, it is whether anyone sees a problem with my solution to the void behind the plasterboard.

Well I do understand there are many items to be placed and most definitely understand clients making changes. Perhaps a gunable spray foam would be your answer.

Jazzdude;

there have been many discussions on this in the past, we have built with OSB, fibercement and metal faced SIPs,  the problem with any wall board directly in contact with the SIPs is the transfer of sound, creating the "drum" effect or hollow sound.
to overcome this,  it is best to isolate the the two surfaces with hi-hat furring or resilient channels.   We use 1-1/2" hi hat and 4 x 4 electrical boxes with a 1/2" plaster ring, this allows sufficient cubic inches required to make 95% of the connections. We still use romex, but it can also be done with MC cable or conduit

We don't have a problem with the plasterboard that is screwed directly to the SIPS, in fact it is quite acceptable here, its the thin hollow sound you get when one sheet of plasterboard is on battens at 600mm centres.

If the XPS or Rockwool batt is nailed to the SIP, gauged out where needed so that the services can be fixed, then the whole thing covered with plasterboard sheeting with screws that go through all, say 50- 60 mm long. The result. You slap the plasterboard and there is no void behind it, except of course where the vertical runs are to the services.

I'm not so sure the Rockwool batts would make it sound any less hollow. If someone is expecting a solid stone or concrete wall, there isn't much you can do to wallboard to replicate that. I guess you could experiment and find out.

We have tried using XPS externally, with direct fixing to the SIPs (we completed checks for interstitial condensation and there were no risks), rendered with mesh, mapatherm and finish and the results were pretty good. A much firmer feel to the wall when comparing it to rendered cement board on battens. This though is rendered directly. On the inside I want to avoid render and use plasterboard on top without battens.

Posted By jazzdude on 16 Dec 2010 07:46 AM
We don't have a problem with the plasterboard that is screwed directly to the SIPS, in fact it is quite acceptable here, its the thin hollow sound you get when one sheet of plasterboard is on battens at 600mm centres.

If the XPS or Rockwool batt is nailed to the SIP, gauged out where needed so that the services can be fixed, then the whole thing covered with plasterboard sheeting with screws that go through all, say 50- 60 mm long. The result. You slap the plasterboard and there is no void behind it, except of course where the vertical runs are to the services.

I think you missed the point

I am not sure I understand what you mean Chris

Posted By jazzdude on 16 Dec 2010 11:34 AM
I am not sure I understand what you mean Chris

Jazzdude;

I was not questioning the direct fastening, we can do it also, The point was an air space aids with sound control.

Another thing that adds to a hollow sound in a home is many "hard" surfaces such as tile, marble, etc., carpet aids in deadening echo or hollow sounds

Jazzdude,

When do you get the thin hollow sound with one sheet of plaster board?  Is this from talking in the room or is it when someone knocks on the wall?  Just curious.

What I get from jazzdude's description is sort of the "feel" of the wall - wobbly, hollow, cheap - which is exactly what wallboard feels like, especially if you're used to living with stone walls.

Posted By Jelly on 16 Dec 2010 09:45 PM
What I get from jazzdude's description is sort of the "feel" of the wall - wobbly, hollow, cheap - which is exactly what wallboard feels like, especially if you're used to living with stone walls.

That's exactly my point, thanks Jelly

Have you tried furring out the wall and then after installing the utilities filling the chase with open cell foam?  Trim the open cell foam flush with the furring strips and then install the plasterboard.  This method should add to the insulation and also reduce the hollow sound.

Posted By Alton on 17 Dec 2010 09:03 AM
Have you tried furring out the wall and then after installing the utilities filling the chase with open cell foam?  Trim the open cell foam flush with the furring strips and then install the plasterboard.  This method should add to the insulation and also reduce the hollow sound.

sounds a lot more time consuming and costly than my original post, but thanks for your input.

It seems Alton's suggestion of using a combination of spray foam and furring strips (battens) would be a good one because it would give a very rigid solid feel. Spray foam really grips and sticks very firmly. True it's probably more expensive and time consuming than placing XPS sheets.

Do you think the XPS would compress when you screw the wallboard through to the SIPs panels? Also would your customers complain that there is nothing to nail or screw to in order to hang pictures or mirrors (without using a 60 mm screw)?

You mentioned render in the initial post (Americans refer to that as plaster). I would think that would be a good option to sort of imitate a stone feel, but maybe you'd prefer not to mess with it.

Posted By Jelly on 20 Dec 2010 08:11 AM

Do you think the XPS would compress when you screw the wallboard through to the SIPs panels? Also would your customers complain that there is nothing to nail or screw to in order to hang pictures or mirrors (without using a 60 mm screw)?

I would expect you would use the same fixings as you would if mounting to wallboard without fixing to a batten. We are leaning towards using rockwool batt, a heavy grade at 175 kg/m, doesn't compress and adds to the fire resistance too.

I think that it will be impossible to avoid battens altogether, especially in key areas such as kitchen etc where weight will be an issue.