"the house's chairs" is not accepted, does it mean it's a not a valid translation (if so, why) ?
Why? Because this is Duolingo Swahili. Somewhere in the world they should be able to find a native speaker of English to clean up the mess. The only reason I put up with this ignorance is that I am actually learning, without clobbering the small pension I live on.
Hapana. Although, you may come across a Swahili saying so, but it's a broken language. But also, your sentence maybe a correct but incomplete one. You will have to provide more information onto it:
"Viti vya nyumba ya jirani" - The neighbour's house chairs
Hope I have cleared your doubt.
Swahili is a language, not a people. It is improper to refer to Swahili speakers as "a Swahili" unless they are of the Swahili tribe, which is a very small subset of Swahili speakers.
I don't know what meaning was intended here. I thought maybe it was different types of chairs, e.g., viti vya nyumbani, viti vya ofisini, viti vya kanisani, viti vya shule(ni) ... but my answer was marked wrong. I still think "house chairs" or "chairs for a home" is a good answer, so I reported it.