VAT Registration Query for Two Companies with Different Activities

I'm seeking some guidance regarding the VAT registration for two limited companies with distinct activities. Company A, established a while ago, is involved in construction works for private clients and is VAT registered. Company B, founded two years ago by the same shareholder/director, focuses on manufacturing shelves and sells them online. Company B is currently not VAT registered. Both companies maintain separate business bank accounts. It's worth noting that the customer bases for these companies are entirely different. Additionally, both companies are registered under the same address. My primary question is: considering the different business activities, the separate customer bases do you think it is necessary to register Company B for VAT, or can it be treated as a separate entity with a different activity? I am also curious about how HMRC might view this arrangement. Could this be considered as VAT disaggregation, given the shared address, even though the companies have distinct activities and customer bases?

Have a read of this HMRC guidance https://www.gov.uk/government/publications/statement-of-practice-4-1983/statement-of-practice-4-1983 You need to be careful around the VAT registered business reclaiming VAT on costs that are not wholly and exclusively used by the VAT registered business, for example if two business share the same premises...then the VAT registered business cannot reclaim all the VAT on rent or service charges or on utilities as clearly some of these costs are enjoyed by the other business. Remember the right to reclaim VAT is that the incurred VAT is used in making taxable supplies, that is not the case if the VAT registered business buys a laptop and reclaims the VAT but then uses the laptop in the unregistered business. So whilst there may not be disaggregation in the truest sense, HMRC could still enquire as to the VAT reclaimed by the VAT registered business.

Hi QQask
Please see the guidance below:
Statement of Practice 4 (1983)
Thank you.