A trading update to the City today revealed revenue for the six months to end- June was down 5% at £167m compared to £177m last year.
The firm said: "After a good first quarter, the exceptionally poor working conditions experienced in April 2012 continued through to the end of June."
Marshalls blamed the bad weather for some of the fall but, underlying sales to the public sector and commercial market – which represent 64% of the company's business – were 2% below last year but "broadly in line with expectations".
Sales to the domestic market were down by 14%. Marshalls is "reducing costs, reducing inventories and conserving cash to mitigate the impact of the reduced sales", the company reported.
The cost-cuts will lead to a one-off charge of £7m but will save £4m a year.
Marshalls said it will continue to invest in growth markets, including street furniture and security products, internal paving and water management products.
The company half-year results for the half-year to end-June will be announced on 31 August.