What Is a SIP House, and How Is It Different From a Normal Timber House?
This is the first article in our series answering the questions clients ask us most often about building on Madeira — and we start with the most basic one: what a SIP house actually is. You can see the full list here.
When somebody hears “timber house”, they usually picture one of two things — and a SIP house is neither of them. Either a mountain cabin made of logs, or an American film scene where a crew nails together a skeleton of studs and then stuffs mineral wool between them.
SIP is neither of those. And the difference is not cosmetic — it changes how the building behaves, especially on an island where it rains sideways for three days and then the sun comes out like nothing happened.
What a SIP house is actually made of
SIP stands for Structural Insulated Panel. It is a sandwich of three layers:
- 15 mm OSB board on the outside
- an insulation core in the middle
- 15 mm OSB board on the inside
The three layers are laminated together in the factory under hydraulic pressure. Once that is done, the panel is one piece. You cannot take it apart into layers again, and that turns out to matter more than it sounds.
The panels we use come in four thicknesses — 110, 170, 210 and 270 mm — and the core thickness is what changes. For Madeira we use EPS exclusively. Not because it is the cheapest option to say out loud, but because EPS does not absorb moisture from the air, and in a climate with permanently high relative humidity that property is worth more than a higher insulation value we do not actually need here.
The system carries ETA 18/0312 (European Technical Assessment), CE marking, and was tested by TSÚS, the Slovak building testing institute. The panels are manufactured by SIPEUROPE in Slovakia and shipped to Madeira in containers.
The one difference that matters: cavities
A classic timber frame house — what the industry calls light frame — is a skeleton. Vertical studs, horizontal members, and empty space between them that gets filled with insulation and then closed up with boards. The whole thing is assembled and closed on site.
A SIP panel has no cavities. It is solid all the way through, and it arrives on site already closed.
Now put that into Madeira conditions.
On a light frame build, the structure sits open on site while it is being assembled. It rains. It is humid even when it does not rain. Moisture inevitably gets into the cavities during construction — and once the walls are closed up, it stays there. Permanently. Nobody sees it, and the client finds out years later.
With SIP house there is nowhere for that to happen. The panel was pressed in a dry, controlled factory environment and it was already full when it arrived. On site we do not laminate anything — we only join panels together, seal the joints with Hydro-Seal gaskets, expanding tape and SIP Spline connections, and add a waterproofing membrane above the insulation as a further layer.
If you want proof that the principle holds under extreme conditions: the manufacturer has a reference houseboat built from the same panels. The structure floats on water.
Three more consequences of having no cavities
It is significantly stronger. Once assembled, the building behaves like a monolithic shell rather than a frame with infill. The structural values come out up to five times higher than a standard timber frame. That is what makes it possible to certify the structure for wind speeds up to 60 m/s — 216 km/h — with static analysis run from sixteen wind directions, plus seismic certification to Portuguese standards.
There are almost no thermal bridges. A frame wall is interrupted by a stud every 60 centimetres, and every stud is a thermal weak point. A SIP house wall has minimal structural timber in it. Thermal resistance comes out at R = 6.5 m²·K/W and above, depending on panel thickness, and the airtightness results in Blower Door tests are at the top of the range. As a side effect, the walls are thinner than a masonry wall of equivalent performance, which gives you 7 to 10 % more usable floor area on the same footprint.
It goes up fast. The panels are cut from a BIM model in the factory and arrive numbered, like a kit. There is no improvisation on site and no waiting for anything to dry. Shell construction — walls, floors, roof — takes 10 to 14 days. Foundations are separate and come before that.
There is also a weight consequence worth mentioning on a steep island: the panel weighs about 22 kg/m², and the finished structure is roughly eight times lighter than masonry. On a sloped plot that translates directly into smaller foundations and less retaining wall, which is one of the few places on Madeira where you can save real money without cutting quality.
The wood we use is not the wood you are picturing
A timber house — the ordinary kind — is built from standard sawn lumber. Cut, often not even dried very well, and put straight to work. That is where most of the “wood does not last” reputation comes from, and with that material, honestly, the reputation is fair.
We do not build with that. Our system always uses three engineered timbers, chosen per project depending on the design and the structural calculation: KVH, BSH and CLT.
KVH is kiln-dried construction timber — dried at high temperature down to around 15 % moisture content. That drying is what matters: at that moisture level the wood is biologically inactive, so it does not support the fungi or insects that need damp wood to live. BSH is glue-laminated timber for the larger structural spans. CLT comes in where the design calls for it.
But the type of wood is not even the main point.
Our timber is never exposed to the weather
Let me put a simple question to you. Have you ever been to Madeira? And if you have — did you see any wood indoors?
Of course you did. Furniture, kitchens, doors, door frames, interior joinery. All of it sits in exactly the same Madeira humidity, and none of it has a lifespan problem. Go further: there are historic houses on this island with timber roof structures that are centuries old and still standing. Visit a museum here — most of them are not specially climate-controlled, they are open to the normal environment — and you will find wooden artefacts several hundred years old with no problem at all. The reason is simple: that wood is under a roof, out of direct sun, out of the direct hit of the weather.
That is the whole point, and it is the argument I use most often with clients who are nervous about wood.
A lot of people will tell you Madeira is a bad place for timber — that wood does not last here. But there is no place on earth where unprotected wood, left exposed to the weather, lasts. Not Madeira, not anywhere. Wherever wood is outside, it has to be protected. That is not a Madeira problem; that is a physics problem, and it is the same everywhere.
How we keep the timber dry
So here is what our system actually does. Our structure is not an exterior. Our structure is an interior — and it is protected far better than a door or a piece of furniture, both of which already survive here for decades, sometimes centuries, without trouble. From the outside, the house looks exactly like a concrete house: render, cladding, whatever the design calls for. There is no visible wood, no structural member sitting out in the salt and the rain.
We protect it two ways. First, by keeping it inside a closed, dry envelope. Second, by sealing that envelope with superior-grade membrane and tape technology — our partner for this is Rothoblaas, whose membranes, tapes and connectors are engineered specifically to keep water and water vapour out of timber structures.
And the assembly as a whole is a diffusion-closed system. The sandwich panel itself acts as a vapour retarder — it slows water vapour from ever migrating into the structure in the first place. So the wood stays dry not by luck, and not by hoping the weather cooperates, but by design.
What SIP house does not change
To be fair about it, because this is where some suppliers get vague.
SIP house does not change the permitting process. Your project goes through the Câmara Municipal like any other building, and it takes the same 9 to 12 months it takes everyone else. The advantage is in execution, not in paperwork.
SIP house does not remove the need for foundations, retaining walls, or connection to utilities. Those depend on your plot, and they are the single largest source of budget surprises on this island.
And SIP house does not fix a bad design. If the geometry is wrong, it is expensive in every technology.
Where this leaves you
If you take one thing from this article, take this: a SIP house and “a timber house” share a raw material and almost nothing else. Different wood, different assembly, different exposure, a different lifespan. Ours is engineered timber — KVH, BSH, CLT — kept dry, sealed to standard, and never left out in the weather. The same wood that already survives here for centuries indoors, only protected far better.
So when someone tells you wood does not last on Madeira, you now know the honest answer: unprotected wood does not last anywhere. Protected wood does. That is the whole difference, and it is designed into the system rather than left to chance.
The real comparison for SIP on Madeira is not against other timber. It is against concrete — humidity, salt, maintenance, speed, and what actually ends up on the invoice. That is the next article in this series.
And if you already have a plot, the most useful thing you can do before committing to anything is a feasibility study on that specific piece of land — what it can carry, and what the foundations and retaining walls will realistically cost. It is usually the cheapest money spent on the whole project.