How to vet a SIP house manufacturer: 12 questions to ask before you sign

Own factory or middleman, what is inside the panel, what warranty you get in writing, how to inspect built houses and what the contract must contain: the questions we would ask ourselves, with the Homebly answers.

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Published: September 4, 2026Updated: October 14, 20264 min read

You vet a SIP house manufacturer in three steps: ask for the factory address and go and see it, ask for a built house you can visit, and ask in writing what the panel contains, what the price covers and what the warranty says. Whoever answers the 12 questions below clearly deserves the contract; whoever dodges them does not. Our factory is in Baia Mare, and what that changes for a plot in the county is a separate article.

Searches for SIP house reviews are full of stories about good houses and bad ones, and the difference almost never comes from the technology, but from who designed the panel, who produced it and who assembled it. We have already written about the real downsides of SIP; this is the article about choosing the partner who keeps them under control. We put the questions to ourselves too; the Homebly answers are in the third column.

The 12 questions, and what a good answer sounds like

Question	Good answer	Homebly's answer
1. Do you have your own factory? Where?	A real address and an invitation to visit.	Yes — our factory is in Baia Mare, Maramureș; the panels are cut and glued there, not at a third party.
2. What is the panel made of?	The layers named, with material classes.	Two OSB boards (emission class E0–E1) and a self-extinguishing expanded polystyrene core.
3. What do you control in production?	Parameters, not adjectives.	The adhesive, the OSB thickness and the polystyrene density, on every panel.
4. Who assembles the structure?	In-house teams trained on this technology.	In Romania our own teams, not occasional subcontractors: one responsibility from production to handover. Abroad, a local contractor.
5. How long does it take, by stage?	Deadlines per stage, not "fast".	The kit about 6 weeks from the deposit (up to 8 if the design is adapted); structure assembly 1–2 weeks; a turnkey house in up to 6 months, permit time not counted.
6. What does it cost and what is included?	A price per design, with a list of what is in and what is out.	Shell on a foundation from €400/m² (no windows), turnkey from €900/m², self-assembly kit from €150/m²; the exact lists are on the pricing page.
7. Is the foundation included?	A clear yes or no, plus how the type is chosen for the plot.	Yes, in the shell on a foundation and in turnkey; the type (strips with a slab, a monolithic slab or concrete piers) is chosen after the geotechnical survey. Without the foundation, the shell starts from €300/m².
8. What warranty do you give, and on what?	The subject and the term of the warranty and who gives it, in the contract.	10 years on the structural integrity of the building, from whoever assembles it: in Romania our own teams do, so the warranty is ours; where a local contractor assembles, the warranty is theirs. On the SIP panels of a house kit, a 10-year factory warranty that they will not delaminate.
9. Can I see built houses?	Yes — and you can talk to the owner.	A visit to an inhabited house, on request.
10. How do you handle ventilation?	It is in the design from the start, properly sized.	Ventilation is designed in from the start, including heat-recovery options; we explain how to use it at handover.
11. What documentation do I get for the permit?	A design adapted to the urban planning certificate.	The plans of the chosen design and the panel layouts; the permit project can be done by us at €15/m² including VAT, or by your own architect.
12. Can the price change along the way?	Not if it is fixed in the contract.	After the consultation you get a fixed price for the whole job, which is not recalculated along the way.

Prices are indicative and shown for general information only: they are “from” figures for the standard design under typical conditions. For your plot, design and specification the final sum may differ; we fix the exact price in the offer after a consultation.

Take the list to the first conversation. The order does not matter; what matters is getting concrete answers rather than "don't worry, we have experience".

Red flags

1. There is no factory address, and a visit "is not possible right now". A middleman reselling someone else's panels can answer neither for production nor for the warranty.

2. "We'll give you any price by tomorrow", without having seen the plot, the design or the finishing level. A serious turnkey price needs a consultation, not a message.

3. A price per square metre without the list of what it includes. "€400/m² here, more elsewhere" says nothing if one price includes windows and roof and the other does not; see what a kit includes.

4. A "lifetime" warranty given verbally. A real warranty has a subject, a term and a signature.

5. A large deposit with no stages. Normal payments follow the stages: production, assembly, finishing, acceptance. How staged payment works is a separate article.

6. No built house you can visit and no client you can talk to.

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Local manufacturer or import: what matters with SIP

The SIP panel is a standardised product; what cannot be imported is the service around it. Three things matter more than the kilometres: who prepares the permit project and at what price, who comes to the site when an assembly problem appears, and whom you claim the warranty from over the next ten years. With a manufacturer whose factory is in the country, all three have an address.

We deliver from Baia Mare across Romania, where our own teams assemble, and to Hungary (the factory is 70 km from the border), where a local contractor we can arrange does the assembly on individually agreed terms; the design is the same, and the structural calculation is done by a local engineer, from €1,000. The difference from a kit brought from far away is not the panel, but that you can come and watch it being made before you pay.

How to inspect built houses

Ask, too, how many years the manufacturer has been working, how many houses it has built and how many of them in Romania. Our answer: 19 years of experience and more than 510 houses built; we have been building in Romania since 2023 and have built 35 houses here. A serious manufacturer tells you the small figure as well as the big one.

Photos show the façade; you want to see what does not show. Ask to visit a house that has been lived in for at least one winter and ask the owner three things: what they paid for heating, whether condensation appeared on windows or in corners, and whether the deadlines in the contract were kept. Look at the joints, the plinth and the places where pipes and cables pass through the walls: that is where the assembly shows.

Comparing technologies is about the design, not fashion: if you are still between options, we have put timber framing and SIP panels side by side on price, timeline and how much depends on the crew on site.

What the contract must contain

The design and the exact delivery list (which panels, which joinery, which roof, which finishes), the fixed price and what is not included, deadlines per stage with dates, payments tied to stages, the subject and term of the warranty, who carries out the assembly, what happens on delay by either side, and the acceptance report, which registering the house also depends on. If a point is missing, ask for it before signing; afterwards it is just a conversation.

All the figures above are in one place with us: the technology page explains the panel and the assembly, and the price list shows what each formula includes. Ask us the 12 questions; at the consultation we answer every one, with the documents on the table.

How do I know whether the company really has a factory?

Ask for the address and go. A SIP panel factory has a hall, a press, a stock of OSB and polystyrene and a production team. If the visit keeps being postponed or "the factory belongs to a partner", you are dealing with a middleman.

Is the price per square metre a good basis for comparison?

Only together with the list of what it includes. At Homebly the shell on a foundation starts from €400/m² and covers the foundation, the panels assembled by our team, floors, roof structure and roof, without windows (an add-on from €30/m²); the turnkey house, from €900/m², adds windows, installations and finishes.

What warranty is normal for a SIP house?

A written one, with a subject, a term and the name of whoever answers for it. Ours is 10 years on the structural integrity of the building, and it comes from whoever assembles the house: from us in Romania, where our own teams build. The service life of the house (from 50 years) is conditional on correct assembly and protection from moisture.

Does it matter whether the manufacturer is in Romania or abroad?

What matters is who answers after delivery: the permit project, coming to the site, and the warranty. With the factory in Baia Mare, all three have an address you can visit.

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