Hello,

I have bought a property with a 13' X 13' wooden workshop attached to the house - Would I need planning permission to knock down the existing wooden workshop and build to the same spec (dimensions) with brick as apposed to wood?

Thanks.

When was the workshop built?

If the workshop is attached to the house it's probably classed as an extension not an outbuilding. If it's 13 foot deep that's more than the 3 meters allowed for an extension to a semi or 4 meters for an extension to a detached house. See guidance on what can be built these days without needing PP here.

http://www.planningportal.gov.uk/permission/commonprojects/extensions/

In short there might be several reasons why the workshop needed PP when it was built. If so did they get it? Find out.  

Lets suppose it needed PP but they didn't get it. If the workshop/extension is more than 4 years old (or 10 years see below) the council cannot take enforcement action. To make it all legal you could apply for a Certificate of Lawful Development on the grounds that enforcement action can no longer be taken and they could not refuse it. If less than 4/10 years old you may have to apply for retrospective planning permission which could be refused.

I say 10 years (rather than 4 years) because it's not clear if the workshop is classed as "residential use", "incidental to the dwelling" or "business use". In cases where there has been an unlawful "change of use" (eg to business use) they have 10 years to issue enforce. If no change of use then they only have 4 years to enforce.

Normally you don't need planning permission for "maintenance" or "repairs" but you do for a knock down and rebuild. This applies even if your house burns down. Once you knock the workshop down it no longer exists and there is a danger the planners will say the new extension has to be lawful in it's own right. They may insist you apply for planning permission or limit you to what you can build under Permitted Development Rights which could be smaller or none at all.

I think I would make sure the existing workshop/extension is legal before you do anything. Get that sorted and then ask the planners if you need PP or a CLD to replace it.