Will a timber building survive Madeira humidity and salt?

This is the most common worry we hear, by a wide margin. And it is a fair one — Madeira is humid, the air near the coast carries salt, and everyone has seen a timber structure somewhere that rotted, warped or fell apart.

So let me answer it properly. But to answer it honestly, we have to turn the question around, because the real question is not “does timber survive here”. It is “what actually survives here, and what doesn’t” — and the answer is not the one most people expect.

We covered the timber side of this in the first article of this series, on what a SIP house actually is: engineered wood, kept inside a dry sealed envelope, never exposed to the weather, the same way the furniture and roof timbers already survive on this island for decades. If you have not read it, start there.

This article is about the other side of the comparison — the one nobody questions. Because the building method everybody trusts on Madeira, the one assumed to be the safe default, has two quiet problems of its own. And they are worth understanding before you decide what “survives” really means here.

The problem is not timber. It is what happens to masonry and concrete here.

Walk around Madeira and look closely at the concrete and masonry houses — not the new show homes, the ones that are ten, fifteen, twenty years old. Look at the staining, the cracking, the render peeling, the rust bleeding through in patches. That is not bad luck. It is what this specific climate does to that specific building method over time.

The trouble splits into two categories: the quality of the waterproofing, and the quality of the concrete itself.

Category one: waterproofing

This is the bigger of the two, and we went deep on it in the previous articles, so I will keep it short here.

A masonry or concrete house is porous. Block, render and concrete all absorb water, and on an island with this much rain and humidity, water is always looking for a way in. The defence against it is the waterproofing strategy — the membranes, the flashings, the sealed detailing, the way windows are set into the wall, the façade. And on most builds here, that strategy is thin. A microns-thick acrylic coating passing as a façade. Standard detailing that we can already see, at the drawing stage, is going to leak. Materials that are not available on the island at the quality the climate actually demands.

We build the opposite way, and the reasons — the imported membranes, the high-silicone façade, the window installation, the drainage detailing — are laid out in the article on fair cost comparison. The short version: our envelope is engineered to keep water out as a complete system, not patched together at the end. A porous wall with a thin coat of paint is not.

Category two: the concrete itself

This is the part almost nobody talks about, and it deserves attention.

Concrete on a humid, salt-carrying island is not the same material as concrete in a dry mainland climate. Two things work against it over time.

First, salt and reinforcement. Concrete is rarely used alone — it is reinforced with steel bars inside it. When chlorides from salt-laden air and moisture penetrate the concrete and reach that steel, the steel corrodes. As it corrodes it expands, and that expansion cracks the concrete from the inside out. You see it as rust stains bleeding through the surface and concrete spalling off in flakes. On a coastal site, this is a slow, quiet, ongoing process for the life of the building.

Second, how the concrete is cured and protected. Concrete needs to be poured, cured and protected under controlled conditions to reach its intended strength and durability. In a wet, humid, sometimes rushed site environment, that control is not always there — and concrete that was compromised at the pour is compromised for good. It is a wet process, done outdoors, exposed to exactly the conditions that work against it.

(A note on precision: the exact mechanisms — chloride ingress, carbonation, curing conditions — behave differently on every site, and I am describing the general pattern, not a lab verdict on any specific house. The point is simply that concrete on this island faces stresses it does not face on the dry mainland.)

Why our system sidesteps both

Here is the part that ties it together.

The main structure of our house is not concrete. It is an engineered timber system, factory-made, dry, sealed, and never exposed. That means the primary carrier of the salt problem — reinforced concrete standing in the weather — is simply not there in the load-bearing structure. There is no steel reinforcement in the walls to corrode, no porous mass soaking up moisture, no wet process cured outdoors in the rain.

Yes, the foundations use concrete — that is unavoidable, and it sits below and is detailed accordingly. But the house itself, the part standing up in the salt air and the rain, is a dry, sealed, engineered envelope. The two problems that quietly age concrete and masonry buildings on Madeira do not have the same grip on it.

So — will it survive?

Turn the original question around one more time.

There is no place on earth where unprotected material — timber, concrete, masonry, anything — survives being left exposed to the weather. The question was never really about timber versus concrete. It is about which system keeps water out and keeps its structure protected, and which one slowly loses that fight.

A porous, reinforced, wet-built structure with thin waterproofing spends its whole life resisting a climate that is patiently working into it. A dry, sealed, engineered envelope with a proper waterproofing strategy does not fight that battle in the same way, because it was built to keep the water on the outside from the start.

So the honest answer is: a properly built SIP house is not the fragile option on this island. Measured against what actually happens to concrete and masonry here over twenty years, it is arguably the more durable one.

The next article in this series looks at how long the whole thing takes — shell construction versus the full project, and why the two numbers are so different.